<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Ginzburg, Orit</style></author><author><style face="normal" font="default" size="100%">Berg, Naama</style></author><author><style face="normal" font="default" size="100%">Steinberger, Yosef</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Do long-lived ants affect soil microbial communities?</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2012</style></year></dates><volume><style face="normal" font="default" size="100%">48</style></volume><pages><style face="normal" font="default" size="100%">227-233</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">&lt;p&gt;This study was designed to test the hypothesis that desert ant species that build nests that remain viable at a particular point in space for more than a decade produce soil conditions that enhance microbial biomass and functional diversity. We studied the effects of a seed-harvester ant, &lt;em&gt;Pogonomyrmex rugosus&lt;/em&gt;, and two generalist ant species, &lt;em&gt;Aphaeonogaster cockerelli&lt;/em&gt; and &lt;em&gt;Myrmecocystus depilis&lt;/em&gt;, on soil microbial communities. Microbial biomass was higher in &lt;em&gt;P. rugosus&lt;/em&gt;-modified soils than in reference soils when soil water content was higher than 3%. Microbial biomass was either higher in reference soils or exhibited no difference in reference soils and nest-modified soils of &lt;em&gt;A. cockerelli &lt;/em&gt;and &lt;em&gt;M. &lt;/em&gt;&lt;em&gt;depilis&lt;/em&gt;. There were differences in microbial functional diversity and microbial community level physiological profiles (MicroResp method) between ant-nest-modified and reference soils of the three ant species on some sampling dates. Temporal pattenrs of soil microbial communities associated with the ant species resulted from differences in soil moisture, density, and species composition of the annual plant c0ommunities associated with the ant nests and in reference areas. Differences in annual plant communities associated with ant nests and surrounding areas resulted in different chemical inputs into the soil organic-matter pools. This study shows that generalizations about the effects of long-lived ant nests on soil biota in arid regions must consider feeding behaviors of the ant species and temporal patterns of rainfall.&lt;/p&gt;</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2012-89968</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Steinberger, Yosef</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Effects of simulated storm sizes and nitrogen on three Chihuahuan Desert perennial herbs and a grass</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2011</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/11-010.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">75</style></volume><pages><style face="normal" font="default" size="100%">861-864</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">&lt;p&gt;Establishment and growth of three perennial herbs and a small tussock grass were studied in an experiment that provided simulated rainfall of 6 mm week_1 or 25 mm once per month and nitrogen fertilization in combination with the different simulated rainfall regimes. Wild onion, Allium macropetalum, failed to establish in plots receiving 25 mm month_1 simulated rainfall. The perennial composite, Bahia absinthifolia, occurred at higher densities in plots that were not irrigated but there were no differences in biomass in any of the irrigation or fertilization treatments. Desert holly, Perezia nana, failed to establish in nitrogen fertilized plots and developed higher abundance and biomass in plots receiving 25 mm month_1. Nitrogen fertilization had either no effect or an adverse effect on the perennial herbs. The tussock grass, Dasychloa pulchella exhibited highest abundance and biomass with 6 mm week_1 added water plus nitrogen. Since global climate change will affect both rain storm frequency and size and atmospheric nitrogen deposition, the results of this study are applicable to understanding vegetation responses climate change.&lt;/p&gt;</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2011-89979</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>5</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Steinberger, Yosef</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Herbivore-plant interactions and desertification in arid lands</style></title><secondary-title><style face="normal" font="default" size="100%">All Flesh is Grass</style></secondary-title><tertiary-title><style face="normal" font="default" size="100%">Cellular Origin, Life in Extreme Habitats and Astrobiology</style></tertiary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2010</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/10-037.pdf</style></url></web-urls></urls><publisher><style face="normal" font="default" size="100%">Springer-Verlas</style></publisher><pages><style face="normal" font="default" size="100%">239-256</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">&lt;p&gt;Arid lands around the world have experienced or are currently experiencing degradation that is known as desertification. Animal-plant interactions that have an effect on desertification are among the most important function of animals in arid ecosystems. Desertification has been defined as land degradation in arid and semiarid areas that is the result of various factors, including climate variation and human activities. The interactions between animals and plants affect desertification arid environments in a number of ways. These interactions may exacerbate desertification processes or contribute to the stability of desertified ecosystems. Some animal-plant interactions are direct, e.g., herbivory, while others are indirect, e.g., seed dispersal and soil modification. Animal-plant interactions that contribute to changes in the structure of plant communities or the spread of alien plant species may enhance some degradation processes such as soil erosion or contribute to soil stability and resistance to degradation.&lt;/p&gt;</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2010-90092</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Steinberger, Yosep</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Pack rats (Neotoma spp.): Keystone ecological engineers?</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2010</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/10-050.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">74</style></volume><pages><style face="normal" font="default" size="100%">1450-1455</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">&lt;p&gt;The potential role of two species of pack rats (&lt;i&gt;Neotoma albigula&lt;/i&gt;) and &lt;i&gt;Neotoma micropus&lt;/i&gt;) as keystone ecological engineers was examined by estimating the species diversity of invertebrates living in the nest middens, and nitrogen mineralization rates in soils associated with the middens. Although pack-rat middens in tarbush (&lt;i&gt;Flourensia cernua&lt;/i&gt;) shrublands were smaller than those in creosotebush (&lt;i&gt;Larrea tridentata&lt;/i&gt;) shrublands, they housed a higher abundance and diversity of arthropods. The &lt;i&gt;Neotoma&lt;/i&gt; spp. middens were an important microhabitat for crickets (&lt;i&gt;Gryllus&lt;/i&gt; sp.), wolf spiders (&lt;i&gt;Lycosa &lt;/i&gt;spp.), and lycid beetle larvae (Lycidae) in all of the shrub habitats. There were five arthropod taxa that occupied all middens in the creosotebush shrubland, and 12 arthropod taxa that occupied all middens in the tarbush shrubland. Soils associated with pack-rat middens had significantly higher soil organic-matter content than reference soils. Nitrogen mineralization was significantly higher in soils associated with pack-rat middens than in reference soils. &lt;i&gt;Neotoma&lt;/i&gt; spp. create habitats with moderate microclimates that are essential for several invertebrates, thus contributing to maintenance of biodiversity. The effects of middens on soil organic matter and nitrogen mineralization create nutrient-rich patches. &lt;i&gt;Neotoma&lt;/i&gt; spp. affect biodiversity and critical ecosystem processes, thus supporting the designation of keystone ecological engineers. &amp;copy; 2010 Published by Elsevier Ltd.&lt;/p&gt;</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2010-90070</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Eldridge, David J.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Duval, Benjamin D.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Animal disturbances promote shrub maintenance in a desertified grassland</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2009</style></year></dates><volume><style face="normal" font="default" size="100%">97</style></volume><pages><style face="normal" font="default" size="100%">1302-1310</style></pages><isbn><style face="normal" font="default" size="100%">doi: 10.1111/j.1365-2745.2009.01558</style></isbn><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">1. Soil disturbance by animals affects the availability of water, nutrients, sediment and seeds, which are critical for the maintenance of functional ecosystems. We examined long-lived faunal structures across six vegetation communities in the northern Chihuahuan desert of New Mexico, USA, testing the proposition that disturbances in undesertified grassland differ in magnitude and effect from those in desertified grassland.2. Vertebrate and invertebrate disturbances totalled 18.9 structures ha)1 across 18 sites. The most common were pits and mounds of American badgers (Taxidea taxus, 32%), nests of the ant Aphaenogaster cockerelli (18.8%) and mounds of kangaroo rats (Dipodomys spectabilis, 31%).3. Desertification was associated with a doubling of the density of structures, but no effects on cover or volume. The greatest density was in desertified mesquite and creosote bush shrublands, and the lowest density in undesertified grass swales. Badger and wood rat (Neotoma sp.) mounds were significant indicators of desertified communities.4. Desertification did not affect the density of kangaroo rat mounds (6.7 ha)1 in black grama grasslands and creosote bush shrublands). However, mounds in creosote bush shrubland were smaller and had more and larger shrubs than adjacent inter-mound hummocks. Desertification was associated with increases in the density of Aphaenogaster cockerelli and Trachymyrmex smithii nests, and declines in Pogonomyrmex rugosus nests. Substantial increases in soil nitrate and electrical conductivity on Myrmecocystus nests were associated with desertification.5. Synthesis. Desertification shaped this desert environment in two main ways. First, while kangaroo rat mound density changed little with desertification, mounds in shrubland continued to enhance shrub persistence long after abandonment, reinforcing desertification processes. Second, marked changes in the density of nests of the key ant species altered the spatial distribution of soil nitrate and electrical conductivity, likely affecting soil fertility and the distribution of desert plants. Our results highlight the importance of animal activity in shaping desert plant communities, and in maintaining or reinforcing desertification processes.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2009-90175</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Eldridge, D.J.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Badger (Taxidea taxus) disturbances increase soil heterogeneity in a degraded shrub-steppe ecosystem</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2009</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/09-002.pdf</style></url></web-urls></urls><pages><style face="normal" font="default" size="100%">66-73</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">In the western United States, overgrazing, weed invasion and wildfire have resulted in the conversion of shrub-steppe to annual grasslands, with substantial effects on ecosystem function. In these lands capes, badgers disturb large areas of soil while foraging for fossorial animals. Mounds created by badgers contained the lowest concentrations of total carbon, nitrogen and sulphur, mineral nitrogen and mineralizable nitrogen, inter-mound soils had the highest concentrations, and excavation pits had intermediate levels. Soil C:N ratio and pH were greater, and electrical conductivity and soluble Ca2þ, Mg2þ and Kþ were lower on mound soils compared with either pit or inter-mound soils. Larger pits generally trapped more litter, and increased litter mass equated with greater concentrations of active carbon, but only at the burned sites. Older mounds supported more vascular plants and cryptogamic crusts. Our results demonstrate reduced levels of nutrients and a higher C:N ratio on the mounds compared with either the pits or inter-mounds. Alteration to the homogeneous post-fire landscape by badgers contributes to patchiness in soils and vegetation, which is critical to the functioning of arid systems. Given their effect on soil C:N ratios, mounds may be important sites for recovery of indigenous shrub-steppe plant species.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2009-90135</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Duval, B.D.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Camel spider (Solifugae) use of prairie dog colonies</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2009</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/09-018.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">69</style></volume><pages><style face="normal" font="default" size="100%">272-276</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Solifugids (camel spiders) are widespread throughout arid regions of western North America and are thought to be important in structuring desert arthropod communities. Despite the ubiquity of camel spiders, little is known about their ecology. Black-tailed prairie dogs (&lt;i&gt;Cynomys ludovicianus&lt;/i&gt;) are also widespread in western North America and are important ecosystem engineers, but they have been reduced in extent because of human activity. Here we report significantly greater numbers of camel spiders on black-tailed prairie dog colonies in southern New Mexico. The difference in vegetation structure created by prairie dog activity is likely the reason for the increased prevalence of camel spiders on colonies. Because camel spiders are important predators and prey, the observation that colonies support higher numbers of these animals provides a mechanism explaining differences in arthropod communities on and off colonies and explaining the preferential foraging behavior of vertebrates associated with prairie dog colonies.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2009-90133</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Ukabi, S.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Steinberger, Y.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Faunal pedturbation effects of soil microarthropods in the Negev Desert</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2009</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/09-015.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">73</style></volume><pages><style face="normal" font="default" size="100%">907-911</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Soil microarthropod communities in seed-harvester ant-nest (Messor spp.) soils and pits excavated by porcupines (Hystrix indica) were examined on a hill-slope catena in the Negev Desert to test the hypothesis that animal-produced soil disturbances increase abundance and diversity of soil biota. There were significantly fewer arthropods and lower taxonomic diversity of soil microarthropods at the top and mid-slope locations, with no consistent patterns of abundance between cool-wet and hot-dry seasons.  Some prostigmatids, cryptostigmatids, and other arthropods in ant-nest, porcupine-pit, and undisturbed soils were more abundant in wet than dry seasons at some locations but more abundant in the hot-dry season at other locations and sample sites. Seven prostigmatid mite families that were relatively abundant in undisturbed soils were absent or of low abundance in ant-nest modified and porcupine-pit soils at mid- and low-slope catena locations. The data result in rejection of the hypothesis. However, the significant effects of topographic position on the catena on soil microarthropod communities emphasize the importance of examining broad spatial patterns and temporal variation before making generalizations about the effects of ecological engineers on arid ecosystem structure and function.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2009-90179</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Kilgore, A.</style></author><author><style face="normal" font="default" size="100%">Jackson, Eric</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Fire in Chihuahuan Desert grassland: Short-term effects on vegetation, small mammal populations, and faunal pedoturbation</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2009</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/09-021.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">73</style></volume><pages><style face="normal" font="default" size="100%">1029-1034</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">&lt;p&gt;A prescribed burn resulted in significant decreases in canopy cover of the grasses: Bouteloua eriopoda, Sporobolus flexuosus, and Aristida purpurea. One year post-burn, basal cover of B. eriopoda remained significantly lower in burned patches than in unburned areas but there were no differences in basal cover of the other perennial grasses. Only one species of the 14 summer annual species occurred in both burned and unburned plots. There were six species of spring annuals in burned patches but no spring annuals in the unburned grassland ten months post-burn. Fire killed 100% of the snakeweed shrubs (Gutierrezia sarothrae), 77% of the Ephedra torreyana shrubs, and 36% of the Yucca elata. All mesquite shrubs that were top-killed by fire, resprouted one month post-burn. Fire had no effect on abundance and species richness of rodents. There were fewer wolf spider, Geolycosa spp. burrows in burned areas than in unburned grassland. The area and volume of soil in termite galleries and sheeting were significantly larger in the unburned grassland than in the burned areas.&lt;/p&gt;</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2009-90196</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Steinberger, Y.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Harvester ants (Hymenoptera: Formicidae) discriminate among artificial seeds with different protein contents</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2009</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/09-009.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">53</style></volume><pages><style face="normal" font="default" size="100%">549-558</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Workers of colonies of the western harvester ant, Pogonomyrmex occidentalis, were recruited to patches of artificial seed of the same caloric value but different protein content. Rates of forager returns with artificial seeds containing five percent protein were nearly twice those of zero percent protein. Differences in foraging rates on artificial seeds of ten and twenty percent protein compared to foraging rates on zero percent protein seeds were not different from the comparison of foraging rates on five percent and zero percent protein seeds.  There were no differences in foraging rates on zero percent protein seeds, 0.5 percent and one percent protein seeds. P. occidentalis presented with patches containing equal amounts of zero, five, ten, and twenty percent protein seeds returned equal amounts of each protein content seed type to the colonies. When presented with high quality seed patches in the same location for four successive days, the rates of forager returns increased over time. When seed patch locations were switched, P. occidentalis' rate of return of zero protein content seeds was the same as for the five percent protein seeds at that location the previous day. Seeds with protein content between one and two percent represent a threshold for seed quality that affects the foraging rate of P. occidentalis workers.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2009-90127</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Noble, J.</style></author><author><style face="normal" font="default" size="100%">Muller, W.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Pfitzner, G.H.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">The significance of termites as decomposers in contrasting grassland communities of semi-arid eastern Australia</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2009</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/09-003.pdf</style></url></web-urls></urls><pages><style face="normal" font="default" size="100%">113-119</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Decomposition of various litter forms including dead tussocks of two native perennial grasses, woollybutt (Eragrostis eriopoda) and mulga mitchell (Thyridolepis mitchelliana), as well as roots of woollybutt, dung of sheep and kangaroo, and bleached toilet rolls, was studied in contrasting grazing exclosures, half of which had termites excluded by biocide (termiticide) treatment. Dead mulga mitchell tussocks decayed more rapidly than woollybutt tussocks during the first 17 months post mortem. Thereafter, rate of decay differed little between species. After 3 years, only small amounts of tussock residues of either species remained and only then did the impact of biocide treatment become significant. Decomposition of kangaroo pellets was typically bimodal with significantly higher decomposition recorded in the controls (no biocide) up to 40 months after treatment, and many intact pellets remaining in the biocide-treated plots. While decomposition of sheep pellets showed similar bimodality, decomposition remained significantly lower in the biocide treatments for the entire duration of the experiment. Results suggest that abiotic processes, including those induced by UV radiation, may be dominant influences mediating decomposition of litter in these semi-arid ecosystems, especially following high rainfall seasons when abundant grass biomass has been generated providing a surfeit of potential forage for harvester termites.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2009-90136</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Roth, G.A.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Steinberger, Y.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Small mammal herbivory: Feedbacks that help maintain desertified ecosystems</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2009</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/09-001.pdf</style></url></web-urls></urls><pages><style face="normal" font="default" size="100%">62-65</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We tested the hypothesis that herbivores contribute to feedbacks maintaining arid ecosystems in a degraded state. We studied small mammal herbivory on a subshrub, broom snakeweed (Gutierrezia sarothrae), and perennial grasses at three sites: (1) ungrazed black grama (Bouteloua eriopoda) grassland; (2) grassland degraded by intense short-duration grazing; and (3) mesquite (Prosopis glandulosa) coppice dunes. Snakeweed was browsed by herbivores primarily during dry winter months. The average percent of G. sarothrae standing crop biomass removed by browsing was 9.2 in ungrazed grassland, 7.4 in intensely grazed grassland, and 4.1 in the dunes. In ungrazed grassland, an average of 12% of grass cover was harvested by herbivores; in the intensely grazed plots – 80%. Herbivore exclusion plots showed that jackrabbits (Lepus californicus) were the primary browsers on snakeweed and rodents on grasses and G. sarothrae inflorescences. Rodent removal of G. sarothrae inflorescences allows wind dispersal of seeds in disturbed and desertified areas, thereby increasing abundance of this poisonous shrub. Grass-tiller cutting by rodents provides a strong feedback that may be responsible for keeping the grass cover low on the intensely grazed areas. Jackrabbit pruning has little effect on G. sarothrae abundance at any stage of desertification.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2009-90137</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Eldridge, D.J.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Soil distrubance by native animals along grazing gradients in an arid grassland</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2009</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/09-026.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">73</style></volume><pages><style face="normal" font="default" size="100%">1144-1148</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Domestic grazing animals that congregate around watering points in arid rangelands create clearly defined trampling-induced grazing gradients. Grazing and trampling alter soil and vegetation condition, often leading to substantial reductions in ecological function. We measured foraging pits and mounds created by native soil foraging animals over 12 months at three watering points in a Chihuahuan Desert grassland, and hypothesized that the density and cover of their disturbances would increase with increasing distance from water. We recorded an average of 3756 disturbances ha_1 and cover of 34.18 m2 ha_1 across the grazing gradients, which comprised mainly pits (43%) and mounds (25%) of heteromyid rodents, ants and spiders. Soil turnover was estimated at 1.43 m3 ha_1. We detected no differences in density, cover, soil volume or composition of disturbances in relation to distance from water, but there were significant, though ill-defined, differences across the five sampling periods, with generally more activity in the warm–wet months. Small animal-created mounds and pits are important sources of soil and sinks for litter within grazing gradients, and may represent the only sites where plants can establish given a relaxation in grazing pressure.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2009-90166</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Ginzburg, O.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Steinberger, Y.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Effects of harvester ant (Messor spp.) activity on soil properties and microbial communities in a Negev Desert ecosystem</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2008</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/08-042.pdf</style></url></web-urls></urls><pages><style face="normal" font="default" size="100%">165-173</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Harvester ants (Messor spp.) function as an essential link between aboveground resources and belowground biota such as the microbial community.  We examine changes in soil microbial biomass and functional diversity resulting from harvester ant (Messor spp.) activity in the Negev Desert, Israel. Abiotic and biotic soil parameters were recorded during two seasons – wet and dry – also representing food availability periods for the ants (low and high seed availability, respectively). Soil samples were collected monthly from the 0- to 10- and 10- to 20-cm soil layers: (1) near the nest entrance, (2) under chaff piles, and (3) at a 2-m radius from the nest entrance (control). Harvester ant activity increased the percentage of organic matter, total soluble nitrogen, and microbial activity in nest-modified soils in comparison to the control soils. Higher CO2 evolution was recorded in the low-seed season in ant nest soils than in the control soils.  During the high-seed season, higher carbon dioxide evolution was recorded only at the nest entrance locations. There were no differences in microbial biomass between the low- and high-seed seasons, but highest microbial biomass was found under chaff in low-seed season and in nest soils in high-seed season. Microbial function diversity was higher in nest-modified soils than in the control soils. This study suggests that the effect of harvester ant nests on soil fertility is due to increased microbial biomass and microbial activity in ant nest-modified soils.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2008-90289</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Barness, G.</style></author><author><style face="normal" font="default" size="100%">Steinberger, Yosef</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Effects of three species of Chihuahuan Desert ants on annual plants and soil properties</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2008</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/08-055.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">72</style></volume><pages><style face="normal" font="default" size="100%">392-400</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">&lt;p&gt;We tested the hypothesis that ant species, which occupy the same nest for a decade or longer, would modify nest soils by increasing soil nutrients and microorganisms resulting in increased biomass, density, cover and species richness of annual plants. We measured soil properties and annual plants on nest soils of three species of Chihuahuan Desert ants (Pogonomyrmex rugosus--seed harvester, Aphaenogaster cockerelli--generalist forager, and Myrmecocystus depilis--liquid collector-insect scavenger) in comparison to paired reference soils at several locations. There were no differences in nest and reference total soil nitrogen of M. depilis and of P. rugosus on three catena soils. Total soil nitrogen of nest-modified soils was higher than of reference soils of A. cockerelli and P. rugosus in a desert grassland site. Soil microbial biomass and respiration were not significantly different among ant species at most locations with the exception of P. rugosus at the base of the catena. Annual plant biomass was higher on M. depilis and A. cockerelli nest soils than on the reference soils. Annual plant biomass was higher on P. rugosus nest soils than on reference soils at the base of the catena and in the grassland but not at the mid-slope and top of the catena. The effects of long-lived ant colony nests on soil properties and vegetation vary in time and space but are independent of the feeding behavior of the ant species.&lt;/p&gt;</style></abstract><issue><style face="normal" font="default" size="100%">4</style></issue><accession-num><style face="normal" font="default" size="100%">LTER.2008-90350</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">James, A.I.</style></author><author><style face="normal" font="default" size="100%">Edridge, D.J.</style></author><author><style face="normal" font="default" size="100%">Koen, T.B.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Landscape position moderates how ant nests affect hydrology and soil chemsitry across a Chihuahuan Desert watershed</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2008</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/08-039.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">23</style></volume><pages><style face="normal" font="default" size="100%">961-975</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Ants moderate the supply of critical resources such as water and nutrients in desert environments by changing the physical arrangement of soils during nest construction. We measured water infiltration and soil physical and chemical properties on and off the nests of two ant species (&lt;i&gt;Pogonomyrmex rugosus, Aphaenogaster cockerelli&lt;/i&gt;) across five sites at differing landscape positions within a Chihuahuan Desert watershed. Our aim was to test whether the effects of these long-lived ant nests on water infiltration and soil chemistry varied between ant species or across sites within a watershed. Water flow was generally slowest at the site with the highest silt and clay contents, and fastest at the site with sandy soils. Flow was generally greater through ant nest soils than adjacent non-nest soils, and we attribute this to increases in macropores in the nests. However, the effects of both ant nests and species varied among sites. Despite wide variation in soil chemical properties across all sites, ant nests had a consistent effect on soil chemical properties, with higher levels of carbon, nitrogen, sulphur, phosphorus and electrical conductivity on nests compared with non-nest soils. Our results demonstrate that while we can generalise about the effects of ant nests on water flow and nutrient levels, differences in soil type, nest density and ant species across sites are likely to moderate these effects.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2008-90221</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Duval, B.D.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Resource regulation by a twig-girdling beetle has implications for desertifi cation</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2008</style></year></dates><volume><style face="normal" font="default" size="100%">33</style></volume><pages><style face="normal" font="default" size="100%">161-166</style></pages><isbn><style face="normal" font="default" size="100%">DOI: 10.1111/j.1365-2311.2007.00928.x</style></isbn><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">1. Resource regulation by insects is the phenomenon by which herbivory enhances resources for the progeny of the herbivore. This report provides an example of resource regulation with implications for desertification in the Chihuahuan Desert of North America.2. Female &lt;i&gt;Oncideres rhodosticta &lt;/i&gt;beetles chew girdles around mesquite ( &lt;i&gt;Prosopis glandulosa &lt;/i&gt;) stems before ovipositing in those stems. The mesquite plants respond by producing compensatory stems below the girdle. Mesquite volume was significantly correlated with the total number of beetle girdles across a suite of low shrub density grassland and high shrub density dune sites, and plants in dune sites had more old and new girdles than mesquite in grasslands.3. Smaller, younger shrubs in grassland responded more vigorously to girdling than did larger, older shrubs in dune landscapes. Stems on shrubs within grassland produced significantly more and longer compensatory stems per girdle than stems on shrubs in dunes. Soil capture by individual plants positively correlated with stem density, and stem density is increasing in the younger plants as a response to beetle damage.4. This study suggests that the interaction between &lt;i&gt;O. rhodosticta &lt;/i&gt;and mesquite is an example of resource regulation that increases the stem density and soil capture ability of mesquite. Because the conversion of productive grasslands to mesquite dune landscapes is one of the most important drivers of desertification in the Chihuahuan Desert, feedbacks between organisms that promote an increase in the size and soil capture ability of mesquite may exacerbate desertification.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2008-90335</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Liu, X.</style></author><author><style face="normal" font="default" size="100%">Monger, H. C.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Calcium carbonate in termite galleries biomineralization or upward transport?</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2007</style></year></dates><volume><style face="normal" font="default" size="100%">82</style></volume><pages><style face="normal" font="default" size="100%">241-250</style></pages><isbn><style face="normal" font="default" size="100%">DOI: 0.1007/s10533-006-9067-x</style></isbn><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Termites and soil calcium carbonate are major factors in the global carbon cycle: termites by their role in decomposition of organic matter and methane production, and soil calcium carbonate by its storage of atmospheric carbon dioxide. In arid and semiarid soils, these two factors potentially come together by means of biomineralization of calcium carbonate by termites. In this study, we evaluated this possibility by testing two hypotheses. Hypothesis 1 states that termites biomineralize calcium carbonate internally and use it as a cementing agent for building aboveground galleries. Hypothesis 2 states that termites transport calcium carbonate particles from subsoil horizons to aboveground termite galleries where the carbonate detritus becomes part of the gallery construction. These hypotheses were tested by using (1) field documentation that determined if carbonate-containing galleries only occurred on soils containing calcic horizons, (2) &lt;sup&gt;13&lt;/sup&gt;C/&lt;sup&gt;12&lt;/sup&gt;C ratios, (3) X-ray diffraction, (4) petrographic thin sections, (5) scanning electron microscopy, and (6) X-ray mapping. Four study sites were evaluated: a C&lt;sub&gt;4&lt;/sub&gt;-grassland site with no calcic horizons in the underlying soil, a C&lt;sub&gt;4&lt;/sub&gt;-grassland site with calcic horizons, a C&lt;sub&gt;3&lt;/sub&gt;-shrubland site with no calcic horizons, and a C&lt;sub&gt;3&lt;/sub&gt;-shrubland site with calcic horizons. The results revealed that carbonate is not ubiquitously present in termite galleries. It only occurs in galleries if subsoil carbonate exists within a depth of 100 cm. &lt;sup&gt;13&lt;/sup&gt;C/&lt;sup&gt;12&lt;/sup&gt;C ratios of carbonate in termite galleries typically matched &lt;sup&gt;13&lt;/sup&gt;C/&lt;sup&gt;12&lt;/sup&gt;C ratios of subsoil carbonate. X-ray diffraction revealed that the carbonate mineralogy is calcite in all galleries, in all soils, and in the termites themselves. Thin sections, scanning electron microscopy, and X-ray mapping revealed that carbonate exists in the termite gut along with other soil particles and plant opal. Each test argued against the biomineralization hypothesis and for the upward-transport hypothesis. We conclude, therefore, that the gallery carbonate originated from upward transport and that this CaCO&lt;sub&gt;3&lt;/sub&gt; plays a less active role in short-term carbon sequestration than it would have otherwise played if it had been biomineralized directly by the termites.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2007-90426</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Rodriguez-Zaragosa, S.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Steinberger, Y.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Effects of temporally persistent ant nests of soil protozoan communities and the abundance of morphological types of amoeba</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2007</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/07-034.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">37</style></volume><pages><style face="normal" font="default" size="100%">81-87</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We compared soil protozoan communities near ant nests with soil protozoans in reference soils 5m from the edge of any mounds.  We sampled three species of Chihuahuan Desert ants that construct nests that persist for more than a decade a seed harvester, Pogonomymex rugosus, a liquid feeding honey-pot ant, Myrmecocystus depilis, and a generalist forager, Aphaenogaster cockerelli.  Ant colonies were located on different topographic positions on catenas of two watersheds.  Total protozoan abundance was higher in P. rugosus nests soils at the tope of a catena and in A. cockerelli nest soils in a grassland than in the respective reference soils.  There were qualitative and quantitative differences in protozoan communities associated with the nests of ants at all locations studied.  Amoebae were the most abundant protozoans at all locations.  Type 1 amoebae (flattened with sub-pseudopodia (like Acanthamoeba) occurred at the highest frequency and was the only amoeba type found in M. depilis nest soils and P. rugosus nest soils at the tope of a catena.  Nanoflagellates were associated with P. rugosus and M. depilis nest soils but were absent from reference soils.  Ciliates, testate amoebae and nanoflagellates were absent from A. cockerelli reference soils but were present in nest soils.  The effects of ants on soil protozoan communities depend on the temporal persistence of the colony, nest building and food handling behavior, topographic position and soil type.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2007-90451</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Zaragoza, Salvador Rodriguez</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Steinberger, Yosef</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Effects of temporally persistent ant nests on soil protozoan communities and the abundance of morphological types of amoeba</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2007</style></year></dates><volume><style face="normal" font="default" size="100%">37</style></volume><pages><style face="normal" font="default" size="100%">81-87</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We compared soil protozoan communities near ant nests with soil protozoans in reference soils 5mfrom the edge of ant mounds.Wesampled three species of Chihuahuan Desert ants that construct nests that persist for more than a decade: a seed harvester, &lt;i&gt;Pogonomyrmex rugosus&lt;/i&gt;, a liquid feeding honey-pot ant, &lt;i&gt;Myrmecocystus depilis&lt;/i&gt;, and a generalist forager, &lt;i&gt;Aphaenogaster cockerelli&lt;/i&gt;. Ant colonies were located on different topographic positions on catenas of two watersheds. Total protozoan abundance was higher in &lt;i&gt;P. rugosus &lt;/i&gt;nest soils at the top of a catena and in &lt;i&gt;A. cockerelli&lt;/i&gt; nest soils in a grassland than in the respective reference soils. There were qualitative and quantitative differences in protozoan communities associated with the nests of ants at all locations studied. Amoebae were the most abundant protozoans at all locations. Type 1 amoebae (flattened with sub-pseudopodia (like &lt;i&gt;Acanthamoeba&lt;/i&gt;)) occurred at the highest frequency and was the only amoeba type found in &lt;i&gt;M. depilis&lt;/i&gt; nest soils and &lt;i&gt;P. rugosus&lt;/i&gt; nest soils at the top of a catena. Nanoflagellates were associated with &lt;i&gt;P. rugosus&lt;/i&gt; and &lt;i&gt;M. depilis&lt;/i&gt; nest soils but were absent from reference soils. Ciliates, testate amoebae and nanoflagellates were absent from &lt;i&gt;A. cockerelli &lt;/i&gt;reference soils but were present in nest soils. The effects of ants on soil protozoan communities depend on the temporal persistence of the colony, nest building and food handling behavior, topographic position and soil type. © 2007 Elsevier B.V. All rights reserved.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2007-90428</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Roth, G.A.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Steinberger, Y.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Jackrabbit (&lt;i&gt;Lepus californicus&lt;/i&gt;) herbivory changes dominance in desertified Chihuahuan Desert ecosystems.</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2007</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/07-016.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">70</style></volume><pages><style face="normal" font="default" size="100%">418-426</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">This study addressed the question: can herbivory by a medium size herbivore, black-tail jackrabbits (&lt;i&gt;Lepus californicus&lt;/i&gt;), change dominance in desertified ecosystems dominated by two species of shrubs. Shrubs that were pruned by jackrabbits in plant communities dominated by creosotebush (&lt;i&gt;Larrea tridentate&lt;/i&gt;) and tarbush (&lt;i&gt;Flourensia cernua&lt;/i&gt;) were compared to shrubs not browsed by the rabbits.  In the missed shrub area, herbivory on F. cernua resulted in death of 46.6% of the shrubs, compared to only 4.8% of L. tridentate shrubs. There was no evidence of jackrabbit browsing of dead &lt;i&gt;F. cernua&lt;/i&gt; in a tarbush monoculture area.  The canopy volumes of F. cernua plants that survived repeated browsing were significantly smaller than predicted based on unbrowsed plants with the same basal stem areas. Jackrabbit browsing resulted in increased canopy volume of creosotebush shrubs. Creosotebush average canopy volume significantly exceeded predicted values because of compensatory growth of stems from nodes below the severed point.  Close spatial association of lightly browsed creosotebush with heavily browsed tarbush may be a factor contributing to low utilization of creosotebush stems by jackrabbits.  Differential browsing by the rabbits is shifting thee ecosystems toward an &lt;i&gt;L. tridentate&lt;/i&gt; monoculture.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2007-90374</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Roth, G.A.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Steinberger, Y.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Jackrabbit (Lepus californicus) herbivory changes dominance in desertified Chihuahuan Desert ecosystems</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2007</style></year></dates><volume><style face="normal" font="default" size="100%">70</style></volume><pages><style face="normal" font="default" size="100%">418-426</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">This study addressed the question: can herbivory by a medium size herbivore, black-tail jackrabbits (&lt;i&gt;Lepus californicus&lt;/i&gt;), change dominance in desertified ecosystems dominated by two species of shrubs. Shrubs that were pruned by jackrabbits in plant communities dominated by creosotebush (&lt;i&gt;Larrea tridentata&lt;/i&gt;) and tarbush (&lt;i&gt;Flourensia cernua&lt;/i&gt;) were compared to shrubs notbrowsed by the rabbits. In the mixed shrub area, herbivory on &lt;i&gt;F. cernua&lt;/i&gt;resulted in death of 46.6% of the shrubs, compared to only 4.8% of &lt;i&gt;L. tridentata&lt;/i&gt;shrubs. There was no evidence of jackrabbit browsing of dead &lt;i&gt;F. cernua&lt;/i&gt;in a tarbush monoculture area. The canopy volumes of &lt;i&gt;F. cernua&lt;/i&gt;plants that survived repeated browsing were significantly smaller than predicted based on unbrowsed plants with the same basal stem areas. Jackrabbit browsing resulted in increased canopy volume of creosotebush shrubs. Creosotebush average canopy volume significantly exceeded predicted values because of compensatory growth of stems from nodes below the severed point. Close spatial association of lightly browsed creosotebushes with heavily browsed tarbush may be a factor contributing to low utilization of creosotebush stems by jackrabbits. Differential browsing by the rabbits is shifting these ecosystems toward an &lt;i&gt;L. tridentata&lt;/i&gt;monoculture. ©2007 Elsevier Ltd. All rights reserved.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2007-90434</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Jackson, E.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Seed harvester ants (&lt;i&gt;Polonomyrmex rugosus&lt;/i&gt;) as &quot;pulse&quot; predators</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2007</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/07-015.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">70</style></volume><pages><style face="normal" font="default" size="100%">549-552</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Seed harvesting ants, Pogonomyrmex rugosus, collected grass cicadas at a high rate (&gt;5 min-1 taken into the nest) at one location where cicada emergence exceeded 3m-2. Dry conditions in the winter-spring resulted in no annual plants in the northern Chihuahuan Desert. P. rugosus colonies were inactive in areas where grass cicada emergence was less than 1 m-2. P. rugosus initiate intense predatory activity in response to pulse of large numbers of prey. This study demonstrates that predatory behavior of seed harvesting ants is not limited to incidental encounters with prey during seed harvesting activities. Pulse predation demonstrates the importance of protein to seed harvester ant colonies.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2007-90373</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>5</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Bestelmeyer, BT</style></author></authors><secondary-authors><author><style face="normal" font="default" size="100%">Schlesinger, W.H.</style></author></secondary-authors></contributors><titles><title><style face="normal" font="default" size="100%">Chihuahuan Desert Fauna: Effects on Ecosystem Properties and Processes</style></title><secondary-title><style face="normal" font="default" size="100%">Structure and Function of a Chihuahuan Desert Ecosystem: The Jornada Basin Long-Term Ecological Research Site</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2006</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/06-063.pdf</style></url></web-urls></urls><publisher><style face="normal" font="default" size="100%">Oxford University Press</style></publisher><pub-location><style face="normal" font="default" size="100%">New York, NY</style></pub-location><pages><style face="normal" font="default" size="100%">247-265</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">This chapter addresses the direct and indirect effects of animals on ecosystem processes and/or their effects on ecosystem properties. This has been the primary focus of animal studies on the Jornada Experimental Range (JER) and the Chihuahuan Desert Rangeland Research Center (CDRRC) during the twentieth century. Early studies dealt with animal species that were thought to reduce the amount of primary production that was available to support livestock. With the establishment of the International Biological Programme (IBP) in the late 1960s and its premise that ecosystems could be modeled based on the energy flow conceptual model, animal studies were designed to measure energy flow through consumer populations. Those studies yielded estimates of consumption of live plant biomass between 1 and 10% of the annual net primary production. It was concluded that, in most ecosystems, consumers process only a small fraction of the net primary production as live plant material and consumers play important roles in ecosystems as regulators of ecosystem processes and a less important role in energy flow. This hypothesis has been the focus of animal studies in the Jornada Basin for nearly 30 years. Studies of animals as regulators of ecosystem processes led to the expansion of this hypothesis to include the effects of animals on ecosystem properties. Expanding the spatial scale of studies from the patch to the watershed and landscape engendered hypotheses that animals have an effect on processes at those scales because of animal activities that affect redistribution of soil and organic matter.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2006-90491</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Mathis, V. L.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Kay, F. R.</style></author><author><style face="normal" font="default" size="100%">Alkon, P.U.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Effects of grazing and shrub removal on small mammal populations in southern New Mexico, USA</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2006</style></year></dates><volume><style face="normal" font="default" size="100%">66</style></volume><pages><style face="normal" font="default" size="100%">76-86</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Between 1995 and 1997, grazing regimes and mesquite (Prosopis glandulosa) shrub removal were combined in a factorial arrangement to assess changes in small mammal communities on the Jornada Experimental Range in southern New Mexico. Small mammals were live-trapped biannually in winter and at the end of the growing season (fall). We examined changes in abundances, species richness, species and biomass diversity, and mean captures and biomass. Species richness did not change significantly with treatments but was seasonally higher in spring 1996 compared to the fall 1996. A decrease in species and biomass diversities were seen in fall 1996 and an increase in both diversities in fall 1997. No plots reached the same species richness, abundance, or diversity encountered during a pre-treatment study in 1993. Spring 1995 and fall 1996 revealed significant reactions to the combination of the applied treatments, yet no overall pattern can be elucidated. Environmental fluctuations such as variable rainfall and inherent stochasticity of the ecosystem may explain the lack of pattern, and only emphasizes the need for more long-term studies assessing the effects of vegetation alteration on dependent communities. © 2005 Elsevier Ltd. All rights reserved.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2006-90552</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Forbes, G. S.</style></author><author><style face="normal" font="default" size="100%">Van Zee, J. W.</style></author><author><style face="normal" font="default" size="100%">Smith, W.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Desert grassland canopy arthropod species richness: temporal patterns and effects of intense, short-duration livestock grazing</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2005</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://www.sciencedirect.com/science?_ob=MImg&amp;_imagekey=B6WH9-4DTP58W-1-1&amp;_cdi=6845&amp;_user=1496926&amp;_orig=browse&amp;_coverDate=03%2F01%2F2005&amp;_sk=999399995&amp;view=c&amp;wchp=dGLbVlz-zSkWb&amp;md5=af0933071b5bfa2dd14b60175e2cc3fb&amp;ie=/sdarticle.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">60</style></volume><pages><style face="normal" font="default" size="100%">627-646</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Arthropods living in the canopies of two woody shrub species (a sub-shrub [Gutierrezia sarothrae] and a large shrub [Prosopis glandulosa]) and perennial grasses, plus associated herbaceous species, were sampled on 18 0.5-hectare plots in a Chihuahuan Desert grassland for 5 consecutive years. Mesquite shrubs were removed from nine plots, six plots were grazed by yearling cattle in August, and six plots were grazed in February for the last 3 years of the 5-year study. Arthropod species richness ranged between 154 and 353 on grasses, from 120 to 266 on G. sarothrae, and from 69 to 116 on P. glandulosa. There was a significant relationship between the number of families of insects on grass and G. sarothrae and growing season rainfall but species richness was not a function of growing season rainfall on any of the plants. Several of the arthropod families that were the most species rich in this grassland were found on all of the plants sampled, i.e. Salticid spiders, Bruchid and Curculionid beetles, Cicadellid and Psyllid homopterans, and ants (Formicidae). There were more species rich families that were shared by grasses and the sub-shrub G. sarothrae than with mesquite. The absence of a relationship between growing season rainfall and species richness was attributed to variation in life history characteristics of arthropods and to the nonlinear responses of annual and perennial desert grassland plants to rainfall. There were no significant differences in insect family or species richness on any of the plant types as a result of removal of mesquite (P. glandulosa) from selected plots. Intense, short duration (24 h) grazing by livestock during late summer resulted in reduced species richness in the grass-herb vegetation layer but had no effect on insect species richness on snakeweed or mesquite shrubs. Livestock grazing in winter had no effect on insect species richness on any of the vegetation sampled.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2005-90601</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Duval, B.D.</style></author><author><style face="normal" font="default" size="100%">Jackson, E.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Mesquite (Prosopis glandulosa germination and survival in black-grama (&lt;i&gt;Bouteloua eriopoda&lt;/i&gt;) grassland: relations between microsite and heteromyid rodent (&lt;i&gt;Dipodomys&lt;/i&gt; spp.) impact</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2005</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/05-004.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">62</style></volume><pages><style face="normal" font="default" size="100%">541-554</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We conducted experiments to examine microsite and rodent influence on mesquite (Prosopis glandulosa) germination and survival in Chihuahuan Desert black-grama (Bouteloua eriopoda) grassland. Simulated caches with mesquite seeds were placed in undisturbed grassland, burned grassland patches with reduced grass cover, and on the periphery of kangaroo rat mounds. Rodent access to cached seeds was controlled by covering half of the caches with mesh domes. Kangaroo rats destroyed dung pats containing scarified mesquite seeds and excavated all seeds in simulated caches during a year in which no grasses or forbs set seed. Germination was the highest in unburned grassland, but over-winter survival was only observed across experiments in burned grassland microsites. A large proportion of seed caches were excavated (1.1–5.5% of the rodent-excluded caches and between 15.6% and 21.1% of the control caches). There were seasonal differences in numbers of emergent seedlings, with a peak in September 2002 following late summer rains. There were no significant differences in numbers of germinants in burned and unburned grassland microsites, but significantly fewer mesquite seeds germinated on banner-tail kangaroo rat mounds. Caches excavated by rodents yielded 46.6% of germinants. This study suggests that scarification of mesquite seeds is not necessary for germination and heteromyid rodents may be responsible for increased mesquite density in grasslands with some mature mesquite plants. The data also suggest that competition between mesquite seedlings and grasses in black-grama grassland is weak because of the physical characteristics of this system.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2005-90605</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>6</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Herrick, J. E.</style></author><author><style face="normal" font="default" size="100%">Van Zee, J. W.</style></author><author><style face="normal" font="default" size="100%">Havstad, KM</style></author><author><style face="normal" font="default" size="100%">Burkett, L.M.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Monitoring Manual for Grassland, Shrubland and Savanna Ecosystems, Volume I: Quick Start</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2005</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://usda-ars.nmsu.edu/monit_assess/PDF_files/Quick_Start.pdf</style></url></web-urls></urls><publisher><style face="normal" font="default" size="100%">The University of Arizona Press</style></publisher><pub-location><style face="normal" font="default" size="100%">Tucson, Arizona</style></pub-location><pages><style face="normal" font="default" size="100%">36</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">This manual describes how to monitor three rangeland attributes: soil and site stability, watershed function and biotic integrity. Nearly everything we value about rangelands depends on these attributes.  Monitoring these three attributes is like monitoring the foundation of our rangeland ecosystems.  The measurements used to monitor these attributes also can be used to generate indicators relevant to specific management objectives, such as maintaining wildlife habitat, biodiversity conservation or producing forage. Quick Start (Vol.I) includes basic methods and instructions for establishing photo points and completing four basic mesurements.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2005-90618</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>6</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Herrick, J. E.</style></author><author><style face="normal" font="default" size="100%">Van Zee, J. W.</style></author><author><style face="normal" font="default" size="100%">Havstad, KM</style></author><author><style face="normal" font="default" size="100%">Burkett, L.M.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Monitoring Manual for Grassland, Shrubland and Savanna Ecosystems</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2005</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://usda-ars.nmsu.edu/monit_assess/PDF_files/Volume_II.pdf</style></url></web-urls></urls><publisher><style face="normal" font="default" size="100%">University of Arizona Press - Distributor</style></publisher><pub-location><style face="normal" font="default" size="100%">Tucson, AZ</style></pub-location><volume><style face="normal" font="default" size="100%">II</style></volume><pages><style face="normal" font="default" size="100%">200</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">This two-volume document is intended to assist a wide range of users, including technicians (data collectors), field crew leaders, ranchers and landowners, land managers, rangeland professionals, and researchers. Volume II provides more detailed guidance on monitoring program design, data analysis and interpretation.  It also includes a number of supplementary methods.Monitoring is part of a broader process in which we use data to test and refine management decisions. Monitoring data allow the collective knowledge of scientists and land managers to be applied to improve resource management.  Monitoring is designed to support a diverse set of goals required by various societal interests. The monitoring procedures described in this manual provide data on three key attributes of landscape and ecosystem sustainability: soil and site stability, hydrologic function, and biotic integrity. These data provide the foundation for assessing and evaluating the degree to which societal goals and/or values are being met by current landscape management. They also provide the basis for management options that meet specific goals.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2005-90660</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Nash, M. S.</style></author><author><style face="normal" font="default" size="100%">Jackson, E.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Effects of intense, short-duration grazing on microtopography in a Chihuahuan Desert grassland</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2004</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://www.sciencedirect.com/science?_ob=MImg&amp;_imagekey=B6WH9-48XD3TW-3-W&amp;_cdi=6845&amp;_user=1496926&amp;_orig=browse&amp;_coverDate=02%2F29%2F2004&amp;_sk=999439996&amp;view=c&amp;wchp=dGLbVlb-zSkWz&amp;md5=c0df2ef989f73f07a1ad8d8c4ec01b40&amp;ie=/sdarticle.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">56</style></volume><pages><style face="normal" font="default" size="100%">383-393</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We studied the effect of three consecutive years of short duration (&lt;48 h per year), and intense grazing (20'40 yearling cows per hectare) on soil surface microtopography in a Chihuhuan Desert grassland. We also studied the effects of shrub removal plus grazing on microtopography. Microtopography was measured in 18 plots (treatments). Treatments were a combination of two factors: (1) three levels of grazing (winter-grazed, summer-grazed, and not grazed), and (2) two levels of habitat structure (shrubs-removed and shrubs-intact). Mesquite (Prosopis glandulosa) shrubs were removed from half of the plots (nine out of 18 plots). The average height of the micromounds, the average depths of intermound depressions, and the number of micromounds were significantly reduced on the grazed plots. Shrub removal had no significant effect on the height of the micromounds or the depth of the intermound depressions of ungrazed plots. There were significant differences in average micromound heights and intermound microdepression depths attributable to the season of grazing. Microtopography was significantly reduced on grazed plots from which shrubs were removed, compared to ungrazed plots, and grazed plots with shrubs present. Grass canopy reduction, and destruction of the micromound structure in a short duration, plus intense grazing results in erosion of micromounds and in-filling of intermound depressions. The loss of microtopography coupled with reduction in vegetation height and cover resulting from short-duration intense grazing by cattle exposed soils to an increased risk of soil erosion Destruction of the micromound/microdepression topography by cattle changes the spatial patterns of water infiltration, and may homogenize nutrients in desert grasslands.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2004-90731</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Kerley, G.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Kay, F. R.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Effects of pocket gophers on desert soils and vegetation</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2004</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://www.sciencedirect.com/science?_ob=MImg&amp;_imagekey=B6WH9-49S75S5-3-3N&amp;_cdi=6845&amp;_user=1496926&amp;_orig=browse&amp;_coverDate=07%2F31%2F2004&amp;_sk=999419997&amp;view=c&amp;wchp=dGLbVzb-zSkWW&amp;md5=10b8cdb758010e99a95984501d4dab44&amp;ie=/sdarticle.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">58</style></volume><pages><style face="normal" font="default" size="100%">155-166</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The effects of pocket gophers (Geomyidae) on soils and vegetation were studied on Chihuahuan Desert and Sonoran Desert catenas for comparison with the effects of pocket gophers on soils and vegetation in mesic environments. Two species of gophers, Thomomys bottae and T. umbrinus, ejecta mounds were located on upper slopes of piedmonts where runoff from mountains increase soil moisture. Geomys arenarius ejecta mounds were restricted to small valley bottoms on ridge and valley mesa topography. Soil bulk density of ejecta mound soils was lower than undisturbed soil at the Chihuahuan Desert sites but not at the Sonoran Desert site. Significantly higher annual plant cover were recorded only for ejecta mounds of the Chihuahuan Desert piedmont. The effects of pocket gopher burrowing differed between the species, with G. arenarius sites showing greater extent of soil disturbance at a local scale, but effects of these disturbances on desert soils vegetation are dependent upon the properties of the undisturbed soil. These findings of limited impacts of burrowing on soil chemistry contrast with the situation in more mesic areas.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2004-90716</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Nash, M. S.</style></author><author><style face="normal" font="default" size="100%">Bradford, D.F.</style></author><author><style face="normal" font="default" size="100%">Franson, S.E.</style></author><author><style face="normal" font="default" size="100%">Neale, A.C.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Heggem, D.T.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Livestock grazing effects on ant communities in the eastern Mojave Desert, USA</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2004</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/04-076.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">4</style></volume><pages><style face="normal" font="default" size="100%">199-213</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The effects of livestock grazing on composition and structure of ant communities were examined in the eastern Mojave Desert, USA for the purpose of evaluating ant communities as potential indicators of rangeland condition. Metrics for ant communities, vegetation, and other ground-cover elements were evaluated as a function of distance from livestock water tanks, which represents a gradient in level of livestock activity in desert settings. Data were collected at six isolated water tanks used by cattle during early summer, with seven plots (90m × 90m; 100 pitfall traps) per tank.   Thirty-eight species of ants were recorded, with an average of 14 ant species per plot. Ant species richness did not differ as a function of distance from the water tank. Also, overall species composition, as measured by a similarity index for species presence/absence for paired-comparisons of plots, did not show differences attributable to the gradient in grazing impact. In contrast, the relative abundance of several taxa and functional groups was significantly related to distance from the water tank. The predominant pattern was for the greatest abundance to occur at the water tank, with little difference in ant abundance among plots away from the water tank. This pattern was shown by the abundant ants species, &lt;i&gt;Conomyrma bicolor&lt;/i&gt; and &lt;i&gt;Pheidole tucsonica,&lt;/i&gt; and the groups &lt;i&gt;Conomyrma&lt;/i&gt; spp., &lt;i&gt;Pheidole&lt;/i&gt; spp., homopteran tenders, and plant foragers. However, two species, &lt;i&gt;Aphaenogaster megommata&lt;/i&gt; and &lt;i&gt;Monomorium wheelerorum&lt;/i&gt; showed the greatest relative abundance at a distance away from the water tank. A number of ant metrics were significantly related to ground-cover metrics (&lt;i&gt;R&lt;/i&gt;&lt;sup&gt;2&lt;/sup&gt;&gt; 0.5). Organic debris was the variable most frequently related significantly to ant abundance metrics, always in a positive direction, followed by cover for perennial grasses, annual forbs, and shrubs, and bare patch size. Ant community metrics in the study region appear to have little potential to serve as indicators of rangeland condition because differences were evident primarily in severely degraded localized conditions rather than in intermediate widespread conditions.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2004-90674</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Turner, S.J.</style></author><author><style face="normal" font="default" size="100%">Johnson, A.R.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Pairwise species associations in the perennial vegetation of the northern Chihuahuan Desert</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2004</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/04-077.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">49</style></volume><pages><style face="normal" font="default" size="100%">1-10</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We analyzed pairwise species associations based on presence/absence data from transects of perennial vegetation at 129 sites located in the northern Chihuahuan Desert.  The sites were chosen to represent the range of commonly encountered desert vegetation types from grassland to shrubland.  Twenty-four significant associations were found, all of which were positive (i.e., the species pairs co-occurred more frequently than would be expected by chance).  Some of the species associations identified by our analysis have been noted in the literature previously but others have not and warrant further investigation.  Given the nature and scale of the data used in our analysis, the associations we uncovered most likely represent species with similarities in ecological requirements or tolerances but might or might not indicate strong interaction at the scale of individual plants.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2004-90708</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">de Soyza, A. G.</style></author><author><style face="normal" font="default" size="100%">Killingbeck, K. T.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Plant water relations and photosynthesis during and after drought in a Chihuahuan Desert arroyo</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2004</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://www.sciencedirect.com/science?_ob=MImg&amp;_imagekey=B6WH9-4BV4TP1-3-V&amp;_cdi=6845&amp;_user=1496926&amp;_orig=browse&amp;_coverDate=10%2F31%2F2004&amp;_sk=999409998&amp;view=c&amp;wchp=dGLbVlb-zSkWb&amp;md5=7c3bb52759785951b87f2cff7a47a299&amp;ie=/sdarticle.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">59</style></volume><pages><style face="normal" font="default" size="100%">27-39</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">In order to understand the physiology and ecology of perennial shrub species occupying the banks of ephemeral streams we studied the plant water relations and gas-exchange characteristics of six perennial shrub species growing along an ephemeral stream (arroyo) in the northern Chihuahuan Desert. Two of the species are restricted to riparian habitats (Brickellia laciniata and Chilopsis linearis), three are classified as semi-riparian (Fallugia paradoxa, Prosopis glandulosa, and Rhus microphylla) and one is considered to be non-riparian (Flourensia cernua). Differences in gas-exchange patterns and water relations emerged among these six species, yet differences among obligate, semi-riparian, and non-riparian classes of species were evident, but not universal. Chilopsis and Brickellia did not develop the low plant water potentials that characterized some semi-riparian (Rhus) and non-riparian species (Flourensia) during periods of drought. Rates of photosynthesis and transpiration were highest in Prosopis throughout the study, and were relatively constant in Chilopsis during and after drought. Whether water became available as channel flow or direct rainfall appeared to play a role in the physiology of these arroyo shrubs.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2004-90694</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Steinberger, Y.</style></author><author><style face="normal" font="default" size="100%">Pen-Mouratov, S.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Soil disturbance by soil animals on a topoclimatic gradient</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2004</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/04-078.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">40</style></volume><pages><style face="normal" font="default" size="100%">73-76</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We measured the area and volume of soil disturbed by various groups of animals at three sites on a topoclimatic gradient in the Judean Desert, Israel. Both the area and volume of soil disturbed by animals correlated with the cumulative precipitation of the winter rain season. Rodent activity accounted for most of the soil disturbance at all sites except for June 2001, when the volume of soil transported to the surface by ants in the construction of nest chambers accounted for most of the soil volume moved at the intermediate rainfall site. The aggregate stability of soil ejected from animal excavations was significantly lower than that of undisturbed soil during and immediately following the winter rain season, but not during the following dry seasons. The quantities of soil moved by ants in the Judean Desert were comparable to quantities moved by ants in the Chihuahuan Desert of North America.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2004-90737</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Nash, M. S.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Understanding an ecological system: an example of temporal and spatial variability of &lt;i&gt;Dorymyrmex (Conomyrma) insana &lt;/i&gt;in a stressed system</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2004</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/04-002.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">3</style></volume><pages><style face="normal" font="default" size="100%">631-637</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The responses of pyramid ants &lt;i&gt;Dorymyrmex (Conomyrma) insana&lt;/i&gt; (Buckley) to structural change (removal of an invasive shrub species) and to an environmental stress (short-term, intense grazing by cattle) are presented from an experiment study in Chihuahuan Desert grassland.  Spatial and temporal responses of &lt;i&gt;D. insana&lt;/i&gt; were examined by analysis of variances, kriging maps, and regression analyses.  There were no significant responses of &lt;i&gt;D. insana&lt;/i&gt; to grazing.  The numerical and spatial responses of ants recorded from pitfall trap data were the same as those recorded from mapping ant nests.  The spatial distribution of D. insana nests was a function of the canopy cover of the invasive, woody shrub, honey mesquite (Fabaceae: &lt;i&gt;Prosopis glandulosa&lt;/i&gt; Torrey) (r = 0.82) and explained 68% of the variability in nest distribution.  The dominant, liquid-feeding ant species (D. insana) responded numerically and spatially to structural change and environmental stress.  Spatially referenced data are as important or more important for monitoring ecosystem change than are numerical data.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2004-90676</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Kemp, P. R.</style></author><author><style face="normal" font="default" size="100%">Reynolds, J. F.</style></author><author><style face="normal" font="default" size="100%">Virginia, R. A.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Decomposition of leaf and root litter of Chihuahuan Desert shrubs: Effects of three years of summer drought</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2003</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://www.sciencedirect.com/science?_ob=MImg&amp;_imagekey=B6WH9-47C45V8-C-1&amp;_cdi=6845&amp;_user=1496926&amp;_orig=browse&amp;_coverDate=01%2F31%2F2003&amp;_sk=999469998&amp;view=c&amp;wchp=dGLzVlz-zSkzk&amp;md5=190946302a8aa1232bb0a2fd96317de6&amp;ie=/sdarticle.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">53</style></volume><pages><style face="normal" font="default" size="100%">21-39</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">One of the more uncertain aspects of nutrient cycling in desert ecosystems is the extent to which decomposition is controlled by water availability.  Some of this uncertainty may be partly related to the duration of the studies and/or differences in the chemical composition of the decaying litter.  We conducted a 3-year field study of rainfall to determine the impact of summer (June through September) drought on decomposition of leaf and root litter of two shrub species (Larrea tridentata and Prosopis glandulosa) in the northern Chihuahuan Desert, New Mexico, USA.  In both species, leaf litter decayed at a faster rate and was less effected by drought than root litter.  Drought had no influence on the rates of decomposition of leaves of either species during the first 18 months but caused decay rates to decline by about 25% during the latter half of the study.  Drought decreased decay of root litter in both species by about 25% throughout the 3 years.  There was a general increase in percent nitrogen (%N) of decomposing leaf litter in both species.  Root litter %N declined slightly in Larrea but remained relatively constant in Prosopis.  Using a modified version of the CENTURY model, we were able to predict most aspects of observed leaf and root litter mass loss and nitrogen dynamics.  Overall, the results of this study suggest that relatively large changes in precipitation produce comparatively small changes in rates of decay of both leaf and root litter.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2003-90830</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Jackson, E.C.</style></author><author><style face="normal" font="default" size="100%">Krogh, S.N.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Desertification and biopedturbation in the northern Chihuahuan Desert</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2003</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://www.sciencedirect.com/science?_ob=MImg&amp;_imagekey=B6WH9-46XHFHW-2-1&amp;_cdi=6845&amp;_user=1496926&amp;_orig=browse&amp;_coverDate=01%2F31%2F2003&amp;_sk=999469998&amp;view=c&amp;wchp=dGLzVlz-zSkzk&amp;md5=9a021426458290aeb6e77813addcb4db&amp;ie=/sdarticle.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">53</style></volume><pages><style face="normal" font="default" size="100%">1-14</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We examined the relationship between biopedturbation (animal-caused soil disturbance) and several vegetation and soil-based indicators of rangeland condition to evaluate the effects of desertification on animal soil disturbance.  The area, volume, and abundance of various biopedturbation types were assessed at 117 sites in south-central New Mexico where vegetative cover and composition had previously been measured.  There were significant relationships between biopedturbation and selected rangeland condition indicators.  Increasing percentages of grass cover were positively associated with increasing total area of biopedturbation.  Increasing percentages of shrub cover and mean bare patch size were negatively associated with total biopedturbation area.  Biopedturbation area and volume were related to indicators of rangeland condition and percent shrub cover best predicts the area of soil disturbed by animals.  This relationship, however, cannot reliably predict total biopedturbation area or the area of soil disturbance types.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2003-90831</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Brown, M.F.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">The effects of termites and straw mulch on soil nitrogen in a creosotebush (Larrea tridentata)-dominated Chihuahuan Desert ecosystem</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2003</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://www.sciencedirect.com/science?_ob=MImg&amp;_imagekey=B6WH9-47C45V8-B-1&amp;_cdi=6845&amp;_user=1496926&amp;_orig=browse&amp;_coverDate=01%2F31%2F2003&amp;_sk=999469998&amp;view=c&amp;wchp=dGLbVlz-zSkWW&amp;md5=80ed07b02ae9f458a6196dadd53f8eaa&amp;ie=/sdarticle.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">53</style></volume><pages><style face="normal" font="default" size="100%">15-20</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The effects of organic matter (wheat straw) and subterranean termites on concentrations of soil nitrogen were measured on insecticide-treated plots to eliminate termites and by adding straw mulch to insecticide-treated and insecticide-untreated plots.  Soil nitrogen was significantly higher, 435 mg g (-1 power) soil at 0-5 cm depth, on plots with no termites than on plots with termites (340 mg g (-1 power) soil).  There were no differences in total soil nitrogen at soil depths of 5-10 cm.  Soil nitrogen was higher in soils with termites than in soils with termites excluded on straw-amended plots.  On the plots without straw amendments, total soil nitrogen was higher in soils without termites than in soils with termites present.  Termites had no significant effect on total soil nitrogen under shrub canopies in comparison with intercanopy soils.  The addition of straw mulch did not result in higher soil nitrogen content in soils without termites.  Termites were more important as effectors of soil nitrogen than addition of organic matter in the form of wheat straw.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2003-90832</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">The functional significance of cemented nest caps of the harvester ant, Pogonomyrmex maricopa</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2003</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://www.sciencedirect.com/science?_ob=MImg&amp;_imagekey=B6WH9-47C45Y8-V-1&amp;_cdi=6845&amp;_user=1496926&amp;_orig=browse&amp;_coverDate=02%2F28%2F2003&amp;_sk=999469997&amp;view=c&amp;wchp=dGLbVzb-zSkzS&amp;md5=866b989778702966a3fc00e97d3aa4d4&amp;ie=/sdarticle.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">53</style></volume><pages><style face="normal" font="default" size="100%">281-284</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Harvester ants, Pogonomyrmex maricopa, construct cemented caps on the sand mound nests in a fine sand dune area.  The caps are approximately 60% calcium carbonate that is transported from the underlying calcium carbonate layers.  The caps protect the nest structure from being eroded away during high-wind periods.  Partial erosion of the cemented caps adds calcium carbonate to the sand dune soils.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2003-90837</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Nash, M. S.</style></author><author><style face="normal" font="default" size="100%">Jackson, E.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Soil microtopography on grazing gradients in Chihuahuan Desert grasslands</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2003</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://www.sciencedirect.com/science?_ob=MImg&amp;_imagekey=B6WH9-47VYKHC-2-1B&amp;_cdi=6845&amp;_user=1496926&amp;_orig=browse&amp;_coverDate=09%2F30%2F2003&amp;_sk=999449998&amp;view=c&amp;wchp=dGLbVzz-zSkWA&amp;md5=de75fc2b1f3eceea4c3f3291d243556e&amp;ie=/sdarticle.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">55</style></volume><pages><style face="normal" font="default" size="100%">181-192</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The significant impacts of livestock in the creation of piospheres centered on water points is the loss of soil microtopography across a `landscape' that has been influenced by many years of livestock grazing.  The size, height, and spatial distribution of micromounds and surrounding depressions were measured by a modified erosion bridge at three distances (50, 450, and 1050 m) from water points in desert grassland pastures in the Jornada Basin, New Mexico, USA. Plots at 50m had fewer micromounds and the mounds were smaller than those recorded on the more distant plots.  Microtopography of plots at 450m from water was not significantly different from that recorded at 50m.  Microtopography of plots that were 1050m from water points was significantly different from that of plots nearer water points.  Strong correlation between microtopography and the cover of long-lived perennial grasses (R2=91%) was found, such dependence could be used for assessing the trend in organic matter content that is in concordance with that of microtopography.  Loss of microtopography from the impact of livestock in piospheres exacerbates erosion processes and contributes to desertification.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2003-90788</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>5</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors><secondary-authors><author><style face="normal" font="default" size="100%">R. Lal</style></author></secondary-authors></contributors><titles><title><style face="normal" font="default" size="100%">Ants</style></title><secondary-title><style face="normal" font="default" size="100%">Encyclopedia of Soil Science</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2002</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/02-084.pdf</style></url></web-urls></urls><publisher><style face="normal" font="default" size="100%">Marcel Dekker, Inc.</style></publisher><pub-location><style face="normal" font="default" size="100%">Columbus, OH</style></pub-location><pages><style face="normal" font="default" size="100%">76-79</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Ants are among the most ubiquitous insects on the planet.  They occur in all biomes except for the extreme polar regions.  In the biomes where ants are abundant, they affect many soil processes that contribute to the creation of patch mosaics that characterize the soils and vegetation of many landscapes.  The abundance and diversity of soil-nesting ants varies from as high as 7,000 colonies per hectare in tropical savanna to as few as 3-4 colonies per hectare on some periodically flooded, fine-textured soil, desert landscape units.  Soil-nesting ants affect critical ecosystem processes, such as nutrient cycling and water redistribution.  Ant nest mounds vary from a few centimeters in height and diameter to less than 1 m in height and less than 2 m diameter.  Ant nests consist of underground, branched networks of galleries and chambers.  Surficial chambers are connected to lower chambers by vertical galleries with branching lateral galleries.  Galleries and chambers vary in size and number depending on the species of ant.  For example, Lasius neoniger, an abundant ant species in temperate North America, constructs tubular galleries of 1.5-5.0 mm in diameter and chambers of 10-20 mm diameter and 30-50 mm in length. The volume of L. neoniger nests range from 20-250 cm (to the third power) and are confined to the upper 70 cm of soil (3).  Other species construct nests to depths ranging from 50 cm to greater than several meters, depending on species-specific behavior, soil type, and landscape position.  Soil profile mixing, texture, physical and chemical property modification of mound soils, soil macroporosity, and geomorphological attributes of ant nest mounds vary with species-specific colony longevity, body size, and numbers of workers of a colony, soil type, and landscape position.  The pedturbation effects of ants are, therefore, dependent on the species composition of the ant community, geomorphic history, soil properties, and topographic position of a landscape unit.  Because most studies of the effects of ants on soils have focused on one or two species, a comprehensive analysis of the combined effects of all ant species on the soils of an ecosystem cannot be made.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2002-90916</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>6</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors><secondary-authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></secondary-authors></contributors><titles><title><style face="normal" font="default" size="100%">Ecology of Desert Systems</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2002</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://www.elsevier.com/wps/find/bookdescription.cws_home/675553/description#description</style></url></web-urls></urls><publisher><style face="normal" font="default" size="100%">Academic Press</style></publisher><pub-location><style face="normal" font="default" size="100%">New York, NY</style></pub-location><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Conventional wisdom considers deserts stark, harsh regions that support few living things.  Most people also believe that water alone makes the desert bloom.  Ecology of Desert Systems challenges these conventional views.  This volume explores a broad range of topics of interest to ecosystem, population, community, and physiological ecologists.  Climate, weather patterns, geomorphology, and wind and water processes are examined as variables that affect the distribution of biota through fundamental ecosystem processes.  Descriptions of morphological, behavioral, and physiological adaptations of desert biota illuminate, through the lens of patch dynamics, principles for understanding observed patterns of primary production, nutrient cycling, and the effects of consumers.  Desertification and the techniques for monitoring and quantifying it is examined within the framework of desert ecosystem patterns and processes.  With 12 chapters and over 70 figures and tables, Ecology of Desert Systems is the only book that covers the entire desert ecosystem at this academic level.  Readers are provided with an excellent reference framework for their desert ecology research.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2002-90907</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Sipos, M.</style></author><author><style face="normal" font="default" size="100%">Andersen, M.C.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Gould, W.R.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Graminivory by &lt;i&gt;Dipodomys ordii &lt;/i&gt;and &lt;i&gt;Dipodomys merriami &lt;/i&gt;on four species of perennial grasses</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2002</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/02-085.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">47</style></volume><pages><style face="normal" font="default" size="100%">276-281</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Kangaroo rats have been described as primarily granivorous; however, they also consume green vegetation.  We investigated selectivity of grasses by kangaroo rats (Dipodomys ordii and D. merriami) presented with four common perennial grass species from the Jornada Basin in the Chihuahuan Desert.  All grass species offered were utilized, and there were differences in utilization.  Our results suggest that water content may underlie these differences, although other factors are not excluded.  Merrian's kangaroo rats removed more tillers from each tussock of grass than Ord's kangaroo rat.  Ord's kangaroo rat may select grasses with higher water content per tiller.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2002-90914</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Krogh, S.N.</style></author><author><style face="normal" font="default" size="100%">Zeisset, M.S.</style></author><author><style face="normal" font="default" size="100%">Jackson, E.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Presence/absence of a keystone species as an indicator of rangeland health</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2002</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://www.sciencedirect.com/science?_ob=MImg&amp;_imagekey=B6WH9-45FC338-3Y-1&amp;_cdi=6845&amp;_user=1496926&amp;_orig=browse&amp;_coverDate=03%2F31%2F2002&amp;_sk=999499996&amp;view=c&amp;wchp=dGLbVtb-zSkWz&amp;md5=3dcde2ac1560a651479d49261431f192&amp;ie=/sdarticle.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">50</style></volume><pages><style face="normal" font="default" size="100%">513-519</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We examined the relationship between a Chihuahuan Desert grassland keystone species (banner-tailed kangaroo rat, Dipodomys spectabilis) and several vegetation and soil indicators of rangeland health in order to define a threshold indicator value for irreversible change in ecosystem structure and function.  The abundance of occupied and/or abandoned D. spectabilis burrow-mounds was assessed at 117 sites in south central New Mexico where previous studies had reported vegetation cover and composition.  The most robust indicator for presence/absence of D. spectabilis was shrub cover.  D. spectabilis did not occur at sites with shrub cover greater than 20%.  It was concluded that a threshold value of 20% shrub cover could be applied to assessment and monitoring of Chihuahuan Desert rangelands because higher shrub cover results in the local extinction of this keystone species.  The combination of data on the presence/absence of a keystone species with vegetation and soil indicators provides a method for identifying thresholds of degradation that may be irreversible.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2002-90908</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Nash, M. S.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Bradford, D.F.</style></author><author><style face="normal" font="default" size="100%">Franson, S.E.</style></author><author><style face="normal" font="default" size="100%">Neale, A.C.</style></author><author><style face="normal" font="default" size="100%">Heggem, D.T.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Ant communities and livestock grazing in the Great Basin, USA</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2001</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://www.sciencedirect.com/science?_ob=MImg&amp;_imagekey=B6WH9-45RFHT2-S-1&amp;_cdi=6845&amp;_user=1496926&amp;_orig=browse&amp;_coverDate=12%2F31%2F2001&amp;_sk=999509995&amp;view=c&amp;wchp=dGLzVzz-zSkzV&amp;md5=3c8f42de3cd48efc80a3999bc5e7c04e&amp;ie=/sdarticle.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">49</style></volume><pages><style face="normal" font="default" size="100%">695-710</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The objectives of this study were to determine if metrics for ant species assemblages can be used as indicators of rangeland condition and to determine the influence of vegetation and ground cover variables, factors often influenced by livestock grazing, on ant communities.  The study was conducted in two areas in the Great Basin: a sagebrush-steppe in southeastern Idaho (n = 30 sites) and salt-desert shrub in western Utah (n = 27 sites).  Sites were selected based on known rangeland conditions (i.e., good, fair, poor) associated with livestock grazing.  Ant communities differed considerably between the two study areas.  Collectively, more ant species occurred at the Idaho sites (30) than at the Utah sites (21), relatively few species (8) occurred in both areas, species richness was significantly greater at the Idaho sites (mean = 12(.)0 species) than the Utah sites (mean = 6(.)9 species), and Formica spp. were diverse (total of 15 species) at the Idaho sites but rate (1 species) at the Utah sites.  In Idaho, all species collectively, generalists and Formica spp., were significantly less abundant on sites in poor condition than that on sites in good or fair condition; whereas in Utah, seed harvesters and Pheidole spp. were significantly more abundant on sites in poor condition than on sites in good or fair condition.  In Idaho, species richness was significantly lower on sites in poor condition.  In Idaho, species richness and relative abundances of several ant groups were significantly related to bare patch size and parameters for cover or species richness of several vegetation groups.  In contract to the comparisons involving sites in poor condition, no differences in any communities in either Idaho or Utah were evident between sites in good and fair condition.  Thus, the ant communities responded only to large changes in rangeland condition and to large differences in climatic/edaphic conditions between the two areas.  Hence, ant community metrics appear to have limited utility as indicators of rangeland condition in the Great Basin.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2001-91056</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Nielson, R</style></author><author><style face="normal" font="default" size="100%">de Soyza, A.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Establishment and effects of establishment of creosotebush, &lt;i&gt;Larrea tridentata&lt;/i&gt;, on a Chihuahuan Desert watershed</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2001</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/01-057.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">47</style></volume><pages><style face="normal" font="default" size="100%">1-10</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Creosotebush (Larrea tridentata) seedlings were planted in plots that were irrigated, plots that were irrigated and fertilized with ammonium nitrate, and plots that were not amended in three plant communities on a Chihuahuan Desert watershed: ungrazed black grama (Bouteloua eriopoda) grassland, creosotebush shrubland, and overgrazed grassland.  No seedlings were planted in one-half of the area of each plot.  No seedlings survived in the black grama grassland or the creosotebush shrubland 2 years after planting.  Growth of established creosotebush shrubs was highest in plots with the lowest grass cover.  Fifteen years after the seedlings were planted in the overgrazed grassland, the area under the shrubs was nearly devoid of perennial grasses and forbs.  The aggregate stability of the soils under the established creosotebush shrubs was significantly lower than the soils in the unplanted split-half of the plots.  Electrical conductivity, calcium, and nitrate were significantly lower in soils under shrubs than soils in the unplanted split-half of the plots.  There were also significant reductions in densities of annual plants growing under the shrubs than in the unplanted split-half of the plots.  Successful establishment of creosotebush in desert grasslands is dependent upon the presence of large patches of soil with no perennial plant cover.  Intense grazing by domestic livestock creates microsites and landscape characteristics favorable for seed dispersal, germination and establishment of creosotebush.  Soil changes resulting from shrub establishment reduce the probability of reestablishing perennial grasses in creosotebush-dominated shrubland.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2001-91047</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Herrick, J. E.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">de Soyza, A. G.</style></author><author><style face="normal" font="default" size="100%">Van Zee, J. W.</style></author><author><style face="normal" font="default" size="100%">Havstad, KM</style></author><author><style face="normal" font="default" size="100%">Seybold, C. A.</style></author><author><style face="normal" font="default" size="100%">Walton, M.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Field soil aggregate stability kit for soil quality and rangeland health evaluations</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2001</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/01-032.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">44</style></volume><pages><style face="normal" font="default" size="100%">27-35</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Soil aggregate stability is widely recognized as a key indicator of soil quality and rangeland health. However, few standard methods exist for quantifying soil stability in the field. A stability kit is described which can be inexpensively and easily assembled with minimal tools. It permits up to 18 samples to be evaluated in under 10 minutes and eliminates the need  for transportation, minimizing damage to soil structure. The kit consists of two 21 x 10.5 x 3.5 cm plastic boxes divided into eighteen 3.5 x 3.5 cm sections, eighteen 2.5 cm diameter sieves with 1.5 mm distance openings and a small spatula used for soil sampling. Soil samples are rated on a scale from 1 to 6 based on a combination of ocular observations of slaking during the first 5 minutes following immersion in distilled water, and the percent remaining on a 1.5 mm sieve after 5 dipping cycles at the end of the 5 minute period. A laboratory comparison yielded a highly significant linear  correlation between the stability class and percent aggregate stability based on oven dry weight remaining after treatment using a mechanical sieve. The relationship was not statistically different for a sandy clay loam and a loamy sand. We have applied the method in a wide variety of agricultural and natural ecosystems throughout western North America, including northern Mexico, and have found that it is highly sensitive to differences in management and plant community composition. Although the field kit cannot replace careful laboratory-based measurements of soil aggregate stability, it can clearly provide valuable information when these more intensive procedures are not possible.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2001-91030</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>5</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors><secondary-authors><author><style face="normal" font="default" size="100%">Prakash, I.</style></author></secondary-authors></contributors><titles><title><style face="normal" font="default" size="100%">Invertebrates: Their effects on the properties and processes of desert ecosystems</style></title><secondary-title><style face="normal" font="default" size="100%">Ecology of Desert Environments</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2001</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/01-055.pdf</style></url></web-urls></urls><publisher><style face="normal" font="default" size="100%">Scientific Publishers</style></publisher><pub-location><style face="normal" font="default" size="100%">Jodhpur, India</style></pub-location><pages><style face="normal" font="default" size="100%">333-356</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">This book chapter summarizes the role of invertebrate animals as regulators of ecosystem processes and their effects on the properties of ecosystem properties in arid lands.  Several groups of invertebrates are key players in decomposition and nutrient cycling processes.  Soil nematodes that feed on bacteria and fungi regulate the population growth of these soil microbes, thereby affecting the rates of decomposition, nitrogen mineralization, and rates of cycling of other nutrients.  Soil nematode populations are regulated by predation by several taxa of mites.  Fungal feeding mites are also directly involved in mineralization processes and are key invertebrates in nutrient cycling because they maintain activity in dry soils.  Soil bacteria, protozoans and nematodes cease activity when soil water potentials fall below the wilting point for agronomic plants.  The most important arid soil animals are termites.  Termites supplant earthworms in arid soils as the animals that process dead plant material.  Termites process between 30% and 70% of dead plants, depending upon the species, and also process much of the dung of large herbivores.  Because of the efficiency of the microflora and microfauna in the hind gut of termites, most of the plant material they consume is converted to carbon dioxide and water.  There is a strong negative correlation between termite abundance and soil organic matter in Chihuahuan Desert rangelands and African rangelands.  Termites are primarily responsible for the low organic carbon content of desert rangeland soils.Pedogenesis (soil formation) in arid environments is significantly affected by invertebrate animals.  Desert snails consume large quantities of soil algae, grind surfaces of exposed limestone and grind soil crusts.  Their fecal material is chemically and physically different from the materials that are ingested, thereby contributing to soil formation.  Burrowing and nest building by ants, isopods, and burrowing spiders results in soil turnover with subsoil deposited on the surface.  This activity is functionally similar to plowing but over geological time periods.  Termites build above-ground nests and foraging galleries and sheeting from subsurface soils, thereby contributing to soil turnover and pedogenesis.In arid rangeland soils invertebrates directly affect hydrological properties of soil by the production of macropores.  Macropores are continuous tubes or spaces (voids) in the soil with diameters larger than spaces in which capillary water movement occurs.  During rains, water moves down macropores by bulk flow.  Bulk flow is rapid and quickly wets deep soil layers around macropores.  Arthropods in order of relative importance for the production of macropores in arid rangelands are: termites, ants, isopods, burrowing spiders, cicadas, and beetles.  Emperical measurements of the effects of subterranean termites on hydrology have shown that infiltration rates on plots with termites are more than double those on plots with termites eliminated.Several species of ants and termites have been documented to be responsible for producing fertile patches in arid rangelands and thereby affecting plant production and plant species composition of the patches.  Insects not only affect plant production by changing soil fertility, some species of Cerambicid beetles and Bostrichid beetles stimulate productivity of mesquite (Prosopis glandulosa) by girdling or boring into stems to provide safe sites for larval development.  Mesquite exhibits compensatory growth by producing a number of stem leaders at nodes below the girdle or bore entrance.  The pruning of shrubs by girdling and boring insects exacerbates the problem of shrublands that resist control efforts and remain in a degraded state.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2001-91048</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Killingbeck, K. T.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Nutrient resorption in shrubs growing by design and by default in Chihuahuan Desert arroyos</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2001</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/01-056.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">128</style></volume><pages><style face="normal" font="default" size="100%">351-359</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">In the northern stretches of the Chihuahuan Desert, the margins of ephemeral stream channels called arroyos support a unique vegetation dominated by a guild of winter-deciduous shrubs.  To explore the dynamics of nutrient conservation in this assemblage of arroyo shrubs, we measured nitrogen (N) and phosphorus (P) resorption efficiency and proficiency in six species of shrubs growing in arroyos in southern New Mexico, USA.  Collectively, these six species were no more efficient or proficient at resorbing N and P from senescing leaves than shrubs growing in other environments.  Resorption efficiency averaged 53% and 50% for N and P, respectively, and resorption proficiency averaged 0.80% and 0.06% for N and P, respectively.  However, resorption varied significantly between species specifically restricted in their distribution to riparian habitats (obligate riparian species) and those that were not.  The two obligate riparian species combined (Brickellia laciniata, Chilopsis linearis) were significantly more efficient and proficient at resorbing N than the non-obligate riparian species combined (Fallugia paradoxa, Flourensia cernua, Prosopis glandulosa, Rhus microphylla). Additionally, both Brickellia and Chilopsis were individually significantly more proficient at resorbing N than any of the other four species. The dichotomy in resorption between obligate riparian species and those that were not may have been the result of the interplay between hydrology, geomorphology, and biology. Because arroyos move in space as the movement of water erodes banks and changes channel location, some plants are found along arroyos only because the arroyos have moved to them. These plants (plants growing by default) may be less well adapted to arroyo margins than obligate riparian species (plants growing by design). Significant differences in resorption between obligate and nonobligate riparian species suggested that evolutionary history and habitat specificity may be added to the list of factors known to influence resorption.  Selected life history traits of the six species did not appear to be related to any measure of resorption, but leaf surface area, specific leaf mass, and nutrient concentrations in green leaves were all correlated with resorption efficiency or proficiency in one or more species.  The only species capable of symbiotic N fixation, Prosopis glandulosa, retained at least 2.3 times more N in its senesced leaves than any other species.  Patterns of resorption in arroyo shrubs strongly indicated that efficiency and proficiency are fundamentally different, complementary measures of resorption.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2001-91071</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Nash, M. S.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Van Zee, J. W.</style></author><author><style face="normal" font="default" size="100%">Havstad, KM</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Ant (Hymenoptera: Formicidae) responses to environmental stressors in the northern Chihuahuan Desert</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2000</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/00-007.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">29</style></volume><pages><style face="normal" font="default" size="100%">200-206</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We studied responses of ant communities to shrub removal and intense, pulse seasonal grazing by domestic livestock for four consecutive years.  Weighted relative abundance and percent of traps in which an ant species occurred were analyzed using randomized, complete block design split in time analysis of variance to test for significant differences between means of ant groups.  The ant community in the Chihuahuan Desert grassland is dominated by small, liquid-feeding ants, Conomyrma insana (Buckley), and large seed harvesting ants, Pogonomyrmex desertorum (Wheeler).  The weighted relative abundance of C. insana was significantly reduced on the plots without shrubs.  The relative abundance of P. desertorum was significantly lower on grazed plots without shrubs than on the ungrazed plots without shrubs.  There were no detectable effects of shrub removal or intense, pulse grazing on the less abundant ant species.  These results suggest the recent encroachment of shrubs into Chihuahuan Desert grasslands has increased the relative abundance of the dominant ant species in these communities.  Intensive grazing by livestock has had an adverse effect on the most abundant seed-harvester, P. desertorum.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2000-91148</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Kerley, G. I. H.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Impact of grazing and desertification in the Chihuahuan Desert: Plant communities, granivores and granivory</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2000</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/00-010.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">144</style></volume><pages><style face="normal" font="default" size="100%">78-91</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Livestock effects on plant communities through overgrazing (desertification) should affect the structure and functioning of semiarid rangeland communities.  We measured plant, granivorous ant and rodent communities and rates of seed removal by rodents and ants in grazed (by livestock) and ungrazed desert grasslands, as well as mesquite and creosotebush shrublands to test hypotheses on the effects of grazing and desertification on ecosystem structure and functioning.  In desert grasslands, grazing reduced the cover of perennial grasses, particularly the dominant Bouteloua eriopoda, but the cover of forbs and shrubs did not differ between treatments.  One species of perennial grass, Dasyochloa pulchellum, increased in grazed grasslands compared with grassland exclosures.  Detrended correspondence analysis showed that grazing caused desert grasslands to shift in community structure towards the shrublands.  There were more seed harvesting ant and rodent species in the creosotebush shrublands than in the grasslands and mesquite shrublands.  Grazing had no effect on the diversity of ants or rodents within grasslands, and detrended correspondence analysis revealed no clear trends in granivorous ant community structure in the grazed and ungrazed grasslands or the mesquite and creosotebush shrublands.  Ants removed more seeds than did rodents in the grassland sites, but rodents removed more seeds than did ants in the creosotebush sites; seed removal rates by rodents and ants were the same in the mesquite sites.  Our data support the hypothesis that livestock grazing leads to a shift from grassland to shrubland in the Chihuahuan Desert with associated changes in the structure and functioning of faunal communities.  Because grasslands support few species and low densities of rodents, seed harvesting ants are the most important granivores in these desert grasslands.  On a larger scale, we therefore hypothesize that the observed dominance of rodents as seed harvesters in the Chihuahuan Desert is a function of the desertification of desert grasslands to shrublands by livestock and that associated feedback effects may complicate the regeneration of degraded communities.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2000-91124</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">de Soyza, A. G.</style></author><author><style face="normal" font="default" size="100%">Van Zee, J. W.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Neale, A.</style></author><author><style face="normal" font="default" size="100%">Tallent-Hallsel, N.</style></author><author><style face="normal" font="default" size="100%">Herrick, J. E.</style></author><author><style face="normal" font="default" size="100%">Havstad, KM</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Indicators of Great Basin rangeland health</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2000</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/00-014.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">45</style></volume><pages><style face="normal" font="default" size="100%">289-304</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Early-warning indicators of rangeland health can be used to estimate the functional integrity of a site and may allow sustainable management of desert rangelands.  The utility of several vegetation canopy-based indicators of rangeland health at 32 Great Basin rangeland locations was investigated.  The indicators were originally developed in rangelands of the Chihuahuan Desert.  Soil resources are lost through wind and water-driven erosion mainly from areas unprotected by plant canopies (i.e. bare soil).  Study sites in Idaho had the smallest bare patches, followed by sites in Oregon. The more arid Great Basin Sagebrush Zone sites in Utah had the largest bare patches.  Several vegetational indicators including percent cover by vegetation, percent cover by life-form, percent cover by sagebrush, and percent cover by resilient species were negatively related to mean bare patch size and are potential indicators of Great Basin rangeland condition.  Plant community composition and the range of bare patch sizes were different at sites in the three locations in Idaho, Oregon and Utah.  Therefore, expected indicator values are location specific and should not be extrapolated to other locations.  The condition of study sites were often ranked differently by different indicators.  Therefore, the condition of rangeland sites should be evaluated using several indicators.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2000-91146</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Liu, X.</style></author><author><style face="normal" font="default" size="100%">Lindemann, W.C.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Steiner, R.L.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Microbial diversity and activity of disturbed soil in the northern Chihuahuan Desert</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2000</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/00-011.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">32</style></volume><pages><style face="normal" font="default" size="100%">243-249</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The effects of intense grazing, seasonal drought, and fire on soil microbial diversity (substrate utilization) and activity in a northern Chihuahuan Desert grassland were measured in summer 1997, winter 2998, and spring 1998.  Intense livestock grazing was initiated in winter 1995, burning occurred in August 1994, and drought stresses were imposed from October 1994 to June 1997.  Microbial diversity was inferred from the carbon substrate utilization patterns in both gram (+) and gram (-) Biolog plates.  Microbial activity was estimated by the activity of selected enzymes.  Neither microbial diversity nor activity was affected by grazing.  The interaction of intense grazing and stress subtreatments only occurred in spring for one set of diversity measurements.  The maximum microbial diversity and activity occurred in the winter-drought-stress subplots in summer and spring.  Burning reduced microbial diversity and most enzyme activities as compared to the control in summer and spring.  Microbial diversity was also lower in summer-drought-stress subplots than in the control in summer and spring.  Microbial diversity was highest in summer, intermediate in winter, and lowest in spring.  Microbial activity was generally higher in summer and lower in winter.  It was concluded that substrate availability was the most important factor affecting the diversity and activity of soil microorganisms within a season.  Soil moisture was not the factor causing differences in microbial diversity and activity among the stress treatments, but it was a predictor for some microbial responses under a particular stress.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2000-91126</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Johnson, A.R.</style></author><author><style face="normal" font="default" size="100%">Turner, S.J.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">de Soyza, A. G.</style></author><author><style face="normal" font="default" size="100%">Van Zee, J. W.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Multivariate characterization of perennial vegetation in the northern Chihuahuan Desert</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2000</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://www.sciencedirect.com/science?_ob=MImg&amp;_imagekey=B6WH9-45FC31M-2J-1&amp;_cdi=6845&amp;_user=1496926&amp;_orig=browse&amp;_coverDate=03%2F31%2F2000&amp;_sk=999559996&amp;view=c&amp;wchp=dGLbVlb-zSkWA&amp;md5=3b4e0268abb40abfb17b1356bf81da82&amp;ie=/sdarticle.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">44</style></volume><pages><style face="normal" font="default" size="100%">305-325</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We surveyed vegetation at 100 sites in southern New Mexico to establish a benchmark for monitoring vegetation change.  Sites were selected in a stratified random design based on a classified AVHRR image.  Two shrubs (Larrea tridentata and Prosopis glandulosa) are the most important contributors to perennial cover in the area.  Principal components analysis (PCA) and detrended correspondence analysis (DCA) both clearly delineate these shrublands from the smaller number of compositionally varied grassland sites.  A latitudinal trend in DCA axis 1 scores suggests that encroachment of shrubs into grasslands is most pronounced in the southern portion of the study area.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2000-91118</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Van Zee, J. W.</style></author><author><style face="normal" font="default" size="100%">Nash, M. S.</style></author><author><style face="normal" font="default" size="100%">Smith, W.E.</style></author><author><style face="normal" font="default" size="100%">Herrick, J. E.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Ants as indicators of exposure to environmental stressors in North American desert grasslands</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1999</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/535.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">54</style></volume><pages><style face="normal" font="default" size="100%">143-171</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><accession-num><style face="normal" font="default" size="100%">LTER.1999-91210</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Eve, M. D.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Havstad, KM</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Applying satellite imagery to triage assessment of ecosystem health</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1999</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/652.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">54</style></volume><pages><style face="normal" font="default" size="100%">205-227</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Considerable evidence documents that certain changes in vegetation and soil result in irreversibly degraded rangeland ecosystems. We used Advanced Very High Resolution Radiometer (AVHRR) imagery to develop calibration patterns of change in the Normalized Difference Vegetation Index (NDVI) over the growing season for selected sites for which we had ground data and historical data characterizing these sites as irreversibly degraded. We used the NDVI curves for these training sites to classify and map the irreversibly degraded rangelands in southern New Mexico. We composited images into four year blocks: 1988-1991, 1989-1992, and 1990-1993. The overlap in pixel classified as irreversibly degraded ranged from 42.6% to 84.3% in year block comparisons. Quantitative data on vegetation composition and cover were collected at 13 sites within a small portions of the study area. Wide coverage reconnaissance of boundaries between vegetation types was also conducted for comparisons with year block maps. The year block 1988-1991 provided the most accurate delineation of degraded areas. The rangelands of southern New Mexico experienced above average precipitation from 1990-1993. The above average precipitation resulted in spatial variable productivity of ephemeral weedy plants on the training sites and degraded rangelands which resulted in much smaller areas classified as irreversibly degraded. We selected imagery for a single year, 1989, which was characterized by the absence of spring annual plant production in order to eliminate the confounding effect of reflectance from annual weeds. That image analysis classified more than 20% of the rangelands as irreversibly degraded because areas with shrub-grass mosaic were included in the degraded classification. The single year image included more than double the area classified as irreversibly degraded by the year blocks. AVHRR imagery can be used to make triage assessment of irreversibly degraded rangeland but such assessment requires understanding productivity patterns and variability across the landscapes of the region and careful selection of the years from which imagery is chosen.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1999-91211</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Atchley, M.C.</style></author><author><style face="normal" font="default" size="100%">de Soyza, A. G.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Arroyo water storage and soil nutrients and their effects on gas-exchange of shrub species in the northern Chihuahuan Desert</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1999</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/643.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">43</style></volume><pages><style face="normal" font="default" size="100%">21-33</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><accession-num><style face="normal" font="default" size="100%">LTER.1999-91177</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Kay, F. R.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Biopedturbation by mammals in deserts: A review</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1999</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/696.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">41</style></volume><pages><style face="normal" font="default" size="100%">203-230</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Disturbance-caused patchiness is important for development and maintenance of spatial and temporal heterogeneity in ecosystems.  Mammals are important agents of biopedturbation (soil disturbance by organisms) which is a major source of patchiness in arid ecosystems.  The contribution of soil disturbance by mammals to heterogeneity is a function of the size and longevity of the soil disturbance.  Foraging pits produced by a variety of mammals are relatively short-lived features that trap plant litter and seeds that are rapidly buried.  These form nutrient-rich germination sites.  High water infiltration rates, a low bulk density rooting environment, and frequently increased soil nutrient content (especially mounds of central-place foragers and larder-hoarders) characterize warren complexes.  Productivity tends to be higher on these mounds and the vegetation tends to differ in composition and richness from the surrounding areas.  Soil ejected from fossorial mammal burrow systems is generally of low bulk density, erodes readily, and varies greatly with respect to concentration of nutrients and organic matter, depending upon the species and landscape in which the species live.  The variability in soil properties of fossorial burrow system ejecta mounds precludes generalizations about the effects of these disturbances on vegetation.  Long-lived features such as Mima-like mounds and heuweltjies are nutrient-rich features that support high productivity and a distinct floral assemblage.  There is a significant relationship between longevity of mammal soil disturbance and size of the disturbance: longevity in years = 9¿33 Area to the 0.735 power.  The data suggest that pedturbation by mammals can be an important force in pedogenesis, in structuring landscapes, and in maintaining heterogeneity inecosystems.  Data on mammalian pedturbation is based on scattered autecological studies.  There is a need for long-term studies that focus on biopedturbation (soil disturbance by invertebrates and vertebrates) as a process at scales from the patch to the landscape.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1999-91194</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Rapport, D. J.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Common properties of arid and aquatic systems</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1999</style></year></dates><volume><style face="normal" font="default" size="100%">49</style></volume><pages><style face="normal" font="default" size="100%">193-203</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Given that regional ecosystems are unique and thus may differ considerably in their normal ranges of primary and secondary productivity, species composition, diversity, and nutrient cycling, and given that each system is exposed to unique combinations of stresses, it might be expected that patterns of response to stresses will be highly variable and unpredictable.  Therefore, it is surprising to discover remarkable similarities in the response of ecosystems to stress (Odum 1985, Rapport et al., 1985; Rapport and Regier, 1995). Stressed ecosystems are characterized by a &quot;distress syndrome&quot; (Rapport et al., 1985) that is indicated not only by reduced biodiversity and altered primary and secondary productivity but also by increased disease prevalence, reduced efficiency of nutrient cycling, increased dominance of exotic species, and increased dominance by smaller, shorter-lived opportunistic species. These signs have been well documented in a number of studies of both terrestrial and aquatic systems (Hilden and Rapport, 1993; Rapport et al., 1995; Whitford, 1995; Epstein and Rapport, 1996; Wichert and Rapport, 1998).  How might this distress syndrome pattern be explained?  By what mechanisms do stressed ecosystems become degraded?  Why has it proven so difficult to rehabilitate stressed ecosystems, even after the initial stresses have been reduced or removed altogether? In this article, we address these and related questions by an empirical examination of three very different regional ecosystems, each of which has had a long history of exposure to multiple anthropogenic and natural stresses.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1999-91184</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Schowalter, Timothy D.</style></author><author><style face="normal" font="default" size="100%">Lightfoot, David C.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Diversity of arthropod responses to host-plant water stress in a desert ecosystem in southern New Mexico</style></title><secondary-title><style face="normal" font="default" size="100%">American Midland Naturalist</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">AND</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1999</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://www.bioone.org/bioone/?request=get-document&amp;issn=0003-0031&amp;volume=142&amp;issue=02&amp;page=0281</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">142</style></volume><pages><style face="normal" font="default" size="100%">281-290</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><issue><style face="normal" font="default" size="100%">2</style></issue><accession-num><style face="normal" font="default" size="100%">LTER.1999-86171</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Effects of habitat characteristics on the abundance and activity of subterranean termites in arid southeastern New Mexico (&lt;i&gt;Isoptera&lt;/i&gt;)</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1999</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/697.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">34</style></volume><pages><style face="normal" font="default" size="100%">493-504</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Amitermes wheeleri was the most abundant termite species in most of the habitats.  Gnathamitermes tubiformans was the most abundant subterranean termite species in habitats dominated by creosotebush, Larrea tridentata.  Subterranean termite abundance measured by numbers of termites extracted from baits, mass of paper removed from baits, proportion of dung pats attacked, and quantities of surface foraging galleries all indicated that subterranean termites were most abundant in mesquite (Prosopis glandulosa) dune and creosotebush habitats and least abundant in grassland and shinnery oak (Quercus harvardii) habitats.  Subterranean termite abundance was not affected by soil stability but by the dominant vegetation.  Subterranean termites consumed more than 80% of the creosotebush leaf litter from litter bags between August and December.  There was no evidence that termites consumed shinnery oak leaves or grass stems and leaves.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1999-91196</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Sobhy, H. M.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Effects of repeated drought on soil microarthropod communities in the northern Chihuahuan Desert</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1999</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/99-002.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">28</style></volume><pages><style face="normal" font="default" size="100%">117-120</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Soil microarthropods were sampled in plots centered on creosotebushes (Larrea tridentata) and in plots centered on mesquite (Prosopis glandulosa) coppice dunes.  Nine plots in each area were covered by rain-out shelters with greenhouse plastic roofs which excluded natural rainfall and nine plots received natural rainfall.  There were differences in the abundance of several mite taxa in soils from the mesquite coppice dune plots.  Some taxa (Stigmaeidae, Nanorchestidae and Entomobryidae) occurred in significantly lower numbers in the soils of the drought plots.  Other taxa (Tarsonemidae and Cunaxidae) were more abundant in the drought plots in the mesquite coppice dunes.  There were no significant differences in the abundance of any of the dominant taxa of soil microarthropods in the drought and control plots centered on creosotebush.  In the creosotebush habitat, there were significantly fewer Prostigmata in the plots exposed to drought.  In an area with both creosotebush and mesquire, there were no significant differences in microarthropod population responses to drought and in recovery from drought.  The differences in responses of soil microarthropods to drought in creosotebush and mesquite habitats are attributed to the differences in soil stability, litter accumulations, and microclimate associated with the shrubs.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1999-91207</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Effects of repeated drought on soil microarthropod communities in the northern Chihuahuan Desert</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1999</style></year></dates><volume><style face="normal" font="default" size="100%">28</style></volume><pages><style face="normal" font="default" size="100%">121-128</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><accession-num><style face="normal" font="default" size="100%">LTER.1999-91220</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Rapport, D. J.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">How ecosystems respond to stress: common properties of arid and aquatic ecosystems</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1999</style></year></dates><volume><style face="normal" font="default" size="100%">49</style></volume><pages><style face="normal" font="default" size="100%">193-203</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Stressed ecosystems are characterized by a &quot;distress syndrome&quot; that is indicated not only by reduced biodiversity and altered primary and secondary productivity but also by increased disease prevalence, reduced efficiency of nutrient cycling, increased dominance of exotic species, and increased dominance by smaller, shorter-lived opportunistic species.  These signs have been well documented in a number of studies of both terrestrial and aquatic systems. How might this distress syndrome pattern be explained?  By what mechanisms do stressed ecosystems become degraded?  Why has it proven so difficult to rehabilitate stressed ecosystems, even after the initial stresses have been reduced or removed altogether? These and related questions are addressed by an empirical examination of three very different regional ecosystems, each of which has had a long history of exposure to multiple anthropogenic and natural stresses.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1999-91224</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Mun, H. T.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Changes in mass and chemistry of plant roots during long-term decomposition on a Chihuahuan Desert watershed</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1998</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/629.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">26</style></volume><pages><style face="normal" font="default" size="100%">16-22</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><accession-num><style face="normal" font="default" size="100%">LTER.1998-91276</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Taylor, H.S.</style></author><author><style face="normal" font="default" size="100%">MacKay, W. P.</style></author><author><style face="normal" font="default" size="100%">Herrick, J. E.</style></author><author><style face="normal" font="default" size="100%">Guerrero, R.A.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Comparison of field methods to detect termite activity in the northern Chihuahuan Desert (Isoptera)</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1998</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/635.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">32</style></volume><pages><style face="normal" font="default" size="100%">1-15</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><accession-num><style face="normal" font="default" size="100%">LTER.1998-91277</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Contribution of pits dug by goannas (&lt;i&gt;Varanus gouldii&lt;/i&gt;) to the dynamics of banded mulga landscapes in eastern Australia</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1998</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/645.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">40</style></volume><pages><style face="normal" font="default" size="100%">453-457</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The densities of pits made by goannas Varanus gouldii were estimated in the three distinct zones of banded mulga landscapes (erosion slope, interception zone, and mulga grove) in paddocks of a grazing study in northwestern New South Wales, Australia.  In lightly and moderately grazed paddocks, soil pits were significantly more abundant in the interception zones (M = 119¿7 m to the -2 degree) than in the groves and erosion slopes (M = 16¿7 m to the -2 degree).  In the overgrazed paddock, there were no differences in densities of pits in any of the zones.  In the groves and erosion slopes, approximately 70-80% of the pits contained litter, seeds, and fruits.  However, on the erosion slopes, less than 20% of the pits contained litter and seeds.  The data support the hypothesis that soil disturbance by Varanus lizards produces a positive feedback mechanism for the viability of the interception zone and the functioning of banded vegetation landscapes.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1998-91268</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>5</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors><secondary-authors><author><style face="normal" font="default" size="100%">Levins, R.</style></author></secondary-authors></contributors><titles><title><style face="normal" font="default" size="100%">The desert grasslands</style></title><secondary-title><style face="normal" font="default" size="100%">Ecosystem Health</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1998</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/639.pdf</style></url></web-urls></urls><publisher><style face="normal" font="default" size="100%">Blackwell Science, Inc.</style></publisher><pub-location><style face="normal" font="default" size="100%">Malden, MA</style></pub-location><pages><style face="normal" font="default" size="100%">313-323</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><accession-num><style face="normal" font="default" size="100%">LTER.1998-91281</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">de Soyza, A. G.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Herrick, J. E.</style></author><author><style face="normal" font="default" size="100%">Van Zee, J. W.</style></author><author><style face="normal" font="default" size="100%">Havstad, KM</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Early warning indicators of desertification: Examples of tests in the Chihuahuan Desert</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1998</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/607.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">39</style></volume><pages><style face="normal" font="default" size="100%">101-112</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><accession-num><style face="normal" font="default" size="100%">LTER.1998-91262</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Nash, M. S.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Van Zee, J. W.</style></author><author><style face="normal" font="default" size="100%">Havstad, KM</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Monitoring changes in stressed ecosystems using spatial patterns of ant communities</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1998</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/631.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">51</style></volume><pages><style face="normal" font="default" size="100%">201-210</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We examined the feasibility of using changes in spatial patterns of ants-distnbution on experimental plots as an indicator of response to environmental stress. We produced contour maps based on relative abundances of the three most common genera of ants based on pit-fall trap captures. Relative abundance of &lt;i&gt;Conomyrma &lt;/i&gt;spp. decreased, relative abundance of &lt;i&gt;Solenopsis &lt;/i&gt;spp. increased, and relative abundance of &lt;i&gt;Pogonomyrmex &lt;/i&gt;spp. remained relatively unchanged. The contour maps showed long-term changes in foraging activity and/or distribution of colonies of ants in response to grazing by domestic livestock. This study demonstrated that analysis of spatial patterns of ant activity derived from relative abundances of ants in pit-fall traps provided interpretable data for developing an indicator of exposure to ecosystem stress.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1998-91263</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>5</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors><secondary-authors><author><style face="normal" font="default" size="100%">Levins, R.</style></author></secondary-authors></contributors><titles><title><style face="normal" font="default" size="100%">Validation of indicators</style></title><secondary-title><style face="normal" font="default" size="100%">Ecosystem Health</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1998</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/640.pdf</style></url></web-urls></urls><publisher><style face="normal" font="default" size="100%">Blackwell Science, Inc.</style></publisher><pub-location><style face="normal" font="default" size="100%">Malden, MA</style></pub-location><pages><style face="normal" font="default" size="100%">205-209</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><accession-num><style face="normal" font="default" size="100%">LTER.1998-91305</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">de Soyza, A. G.</style></author><author><style face="normal" font="default" size="100%">Van Zee, J. W.</style></author><author><style face="normal" font="default" size="100%">Herrick, J. E.</style></author><author><style face="normal" font="default" size="100%">Havstad, KM</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Vegetation, soil, and animal indicators of rangeland health</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1998</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/641.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">51</style></volume><pages><style face="normal" font="default" size="100%">179-200</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We studied indicators of rangeland health on benchmark sites with long, well documented records of protection from stress by domestic livestock or histories of environmental stress and vegetation change. We measured ecosystem properties (metrics) that were clearly linked to ecosystem processes. We focused on conservation of soil and water as key processes in healthy ecosystems, and on maintenance of biodiversity and productivity as important functions of healthy ecosystems. Measurements from which indicators of rangeland health were derived included: sizes of unvegetated patches, cover and species composition of perennial grasses, cover and species composition of shrubs and herbaceous perennials, soil slaking, and abundance and species composition of the bird fauna. Indicators that provided an interpretable range of values over the gradient from irreversibly degraded sites to healthy sites included: bare patch index, cover of long-lived grasses, palatability index, and weighted soil surface stability index. Indicators for which values above a threshold may serve as an indicator of rangeland health include: cover of plant species toxic to livestock, cover of exotic species, and cover of increaser species. Several other indicator metrics were judged not sensitive nor interpretable. Examples of application of rangeland health indicators to evaluate the success of various restoration efforts supported the contention that a suite of indicators are required to assess rangeland health. Bird species diversity and ant species diversity were not related to the status of the sample site and were judged inadequate as indicators of maintenance of biodiversity.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1998-91264</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Peters, A. J.</style></author><author><style face="normal" font="default" size="100%">Eve, M. D.</style></author><author><style face="normal" font="default" size="100%">Holt, E. H.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Analysis of desert plant community growth patterns with high temporal resolution satellite spectra</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1997</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/593.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">34</style></volume><pages><style face="normal" font="default" size="100%">418-432</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><accession-num><style face="normal" font="default" size="100%">LTER.1997-91331</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Desertification and animal biodiversity in the desert grasslands of North America</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1997</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/600.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">37</style></volume><pages><style face="normal" font="default" size="100%">709-720</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><accession-num><style face="normal" font="default" size="100%">LTER.1997-91336</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Kerley, G.I.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Kay, F. R.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Mechanisms for the keystone status of kangaroo rats: graminivory rather than granivory?</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1997</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/591.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">111</style></volume><pages><style face="normal" font="default" size="100%">422-428</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><accession-num><style face="normal" font="default" size="100%">LTER.1997-91350</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Van Zee, J. W.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Smith, W.E.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Mutual exclusion by dolichoderine ants on a rich food source</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1997</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/599.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">42</style></volume><pages><style face="normal" font="default" size="100%">229-231</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><accession-num><style face="normal" font="default" size="100%">LTER.1997-91353</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">de Soyza, A. G.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Herrick, J. E.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Sensitivity testing of indicators of ecosystem health</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1997</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/509.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">3</style></volume><pages><style face="normal" font="default" size="100%">44-53</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The sensitivities of three indicators of ecosystem health were evaluated at several sites in the Jornada Basin of the Chihuahuan Desert. The size of bare patches, proportion of total grass cover contributed by long-lived perennial grasses and soil stability are interdependent indicators of ecosystem functions related to the retention and use of water and nutrients. Sensitivity tests were chosen using data collected&lt;i&gt;&lt;/i&gt;along disturbance gradients and then tested using independent, ungrazed exclosures and adjacent grazed pastures. The mean size of bare soil patches was sensitive to anthropogenic disturbance. When bare soil patch data were transformed usiing natural logarithms, the skewness of the frequency distribution weighted by mean bare patch size could be used to indicate early disturbance to the ecosystem. The proportion of total vegetation that was long-lived also was sensitive to anthropogenic disturbance and appears to be a good indicator of ecosystem degradation. The slake test for soil surface stability was extremely sensitive to disturbance and may serve as an early-warning indicator of soil degradation for the coarse-textured soils which were evaluated.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1997-91325</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Anderson, J.</style></author><author><style face="normal" font="default" size="100%">Rice, P. M.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Stemflow contribution to the &quot;fertile island&quot; effect in creosotebush, &lt;i&gt;Larrea tridentata&lt;/i&gt;</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1997</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/602.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">35</style></volume><pages><style face="normal" font="default" size="100%">451-457</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><accession-num><style face="normal" font="default" size="100%">LTER.1997-91364</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">de Soyza, A. G.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Martinez-Meza, E.</style></author><author><style face="normal" font="default" size="100%">Van Zee, J. W.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Variation in Creosotebush (Larrea tridentata) canopy morphology in relation to habitat, soil fertility and associated annual plant communities</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1997</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/510.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">137</style></volume><pages><style face="normal" font="default" size="100%">13-26</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Differences in creosotebush (&lt;i&gt;Larrea tridentata&lt;/i&gt;) crown morphology may reflect chances in relative demand for water vs. nutrient resources, coinciding with shrub growth and development. Creosotebushes with inverted, cone-shaped crowns were more abundant in water-limited environments; whereas, hemispherical-shaped creosotebushes were more abundant in less water-limited environments. Cone-shaped creosotebushes accumulated substantially less litter under their canopies than did creosotebushes with hemispherical-shaped crowns. Soil nutrient concentrations under conical shrubs were similar to those in intershrub spaces and both of these were less than soil nutrient concentrations under hemispherical shrubs. In ecosystems where overland flow of water exerted a greater influence on movement of organic litter than did wind, shrub shape had little effect on long-term litter accumulation. No persistent differences in the biomass or diversity of ephemeral taxa exploiting undershrub areas were found, probably because the positive effects of greater nutrient resources under hemispherical shrubs were offset by the limitations imposed by the larger, more dense canopies of hemispherical shrubs. Overall, creosotebush morphology affected litter accumulation patterns and soil nutrient patterns and must be considered when assessing the heterogeneity of desert ecosystems in the southwestern U.S.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1997-91365</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">de Soyza, A. G.</style></author><author><style face="normal" font="default" size="100%">Franco, A. C.</style></author><author><style face="normal" font="default" size="100%">Virginia, R. A.</style></author><author><style face="normal" font="default" size="100%">Reynolds, J. F.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Effects of plant size on photosynthesis and water relations in the desert shrub &lt;i&gt;Prosopis glandulosa&lt;/i&gt; (Fabaceae)</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1996</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/471.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">83</style></volume><pages><style face="normal" font="default" size="100%">99-105</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The Jornada del Muerto Basin of southern New Mexico has undergone a marked transition of plant communities. Shrubs now dominate areas that were previously dominated by perennial grasses. The replacement of grasses by shrubs requires an establishment phase where small shrubs must compete with similar-sized grass plants. This is followed by a phase in which established shrubs sequester nutrients and water within their biomass and alter soil resources under their canopy, creating “islands</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1996-91407</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Noble, J.C.</style></author><author><style face="normal" font="default" size="100%">Tongway, D.J.</style></author><author><style face="normal" font="default" size="100%">Roper, M.M.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Fire studies in Mallee (&lt;i&gt;Eucaluptus&lt;/i&gt; spp.) communities of western New South Wales: Spatial and temporal fluxes in soil chemistry and soil biology following prescribed fire</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1996</style></year></dates><volume><style face="normal" font="default" size="100%">2</style></volume><pages><style face="normal" font="default" size="100%">398-413</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><accession-num><style face="normal" font="default" size="100%">LTER.1996-91410</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Killingbeck, K. .</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">High foliar nitrogen in desert shrubs: An important ecosystem trait or defective desert doctrine?</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1996</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/495.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">77</style></volume><pages><style face="normal" font="default" size="100%">1728-1737</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><accession-num><style face="normal" font="default" size="100%">LTER.1996-91411</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">The importance of the biodiversity of soil biota in arid ecosystems</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1996</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/504.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">5</style></volume><pages><style face="normal" font="default" size="100%">185-195</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><accession-num><style face="normal" font="default" size="100%">LTER.1996-91412</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Martinez-Meza, E.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Stemflow, throughfall and channelization of stemflow by roots in three Chihuahuan Desert shrubs</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1996</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://www.sciencedirect.com/science/journal/01401963</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">32</style></volume><pages><style face="normal" font="default" size="100%">271-287</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><accession-num><style face="normal" font="default" size="100%">LTER.1996-91428</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Herrick, J. E.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Assessing the quality of rangeland soils: Challenges and opportunities</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1995</style></year></dates><volume><style face="normal" font="default" size="100%">50</style></volume><pages><style face="normal" font="default" size="100%">237-242</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><accession-num><style face="normal" font="default" size="100%">LTER.1995-91452</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>5</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Forbes, Gregory S.</style></author><author><style face="normal" font="default" size="100%">Kerley, Graham I.</style></author></authors><secondary-authors><author><style face="normal" font="default" size="100%">Van Devender, T. R. , eds.</style></author></secondary-authors></contributors><titles><title><style face="normal" font="default" size="100%">Diversity, spatial variability, and functional roles of invertebrates in desert grassland ecosystems</style></title><secondary-title><style face="normal" font="default" size="100%">The Desert Grassland</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1995</style></year></dates><publisher><style face="normal" font="default" size="100%">University of Arizona Press</style></publisher><pub-location><style face="normal" font="default" size="100%">Tucson, AZ</style></pub-location><pages><style face="normal" font="default" size="100%">152-195</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Any analysis of the community structure and functional roles of desert grassland invertebrates is constrained by the fact that there are few, if any, patches of grasslands undisturbed by humans and their domestic livestock.  The desert grasslands currently exist as scattered patches surrounded by large expanses of desertscrub or as a grassland matrix with shrubs.  Much of the area that was desert grassland in the 1850s is now classified as desertscrub (Buffington and Herbel 1965; York and Dick-Peddie 1969).  Further, the remaining desert grassland remnants are diverse in terms of soil characteristics and grass species composition.  In some areas, exotic introduced grasses have become dominant; in others, remnant grasslands are dominated by species of grasses that are relatively unpalatable to domestic livestock.     The invertebrate fauna of desert grasslands is incredibly diverse and includes several phyla.  while mammal, bird, reptile, and vascular plant species occur in the tens to hundreds, invertebrate species in desert grasslands number in the thousands or tens of thousands, and many of the less conspicuous species have never been described by taxonomists.  Much of this fauna is never seen by the casual observer.  If you were asked, &quot;What invertebrates did you see on your morning walk in the desert grassland?&quot; your response would probably be &quot;ants.&quot;  Ants are the most conspicuous and, along with unseen subterranean termites, the most numerous macroinvertebrates in arid environments.  However, the fauna of desert grasslands includes many microscopic organisms and many large but cryptic species as well as the obvious and familiar ones (Crawford 1981; Wallwork 1982).  Most of what we know about desert grassland invertebrates and their general life history characteristics is based on data from economically important species (Crawford 1981).</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1995-91457</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Fisher, F. M.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Field simulation of wet and dry years in the Chihuahuan Desert: Soil moisture, N mineralization and ion exchange resin bags</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1995</style></year></dates><volume><style face="normal" font="default" size="100%">20</style></volume><pages><style face="normal" font="default" size="100%">137-146</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><accession-num><style face="normal" font="default" size="100%">LTER.1995-91463</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">N.E. West</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">The intersection of ecosystem and biodiversity concerns in the management of rangelands</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1995</style></year></dates><volume><style face="normal" font="default" size="100%">IV</style></volume><pages><style face="normal" font="default" size="100%">72-79</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><accession-num><style face="normal" font="default" size="100%">LTER.1995-91464</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Martinez-Turanzas, G</style></author><author><style face="normal" font="default" size="100%">Martinez-Meza, E.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Persistence of desertified ecosystems: explanations and implications</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1995</style></year></dates><volume><style face="normal" font="default" size="100%">37</style></volume><pages><style face="normal" font="default" size="100%">319-332</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Studies of rainfall partitioning by shrubs, responses of shrub-dominated ecosystems to herbicide treatment, and experiments using drought and supplemental rainfall were conducted to test the hypothesis that the shrub-dominated ecosystems that have replaced desert grasslands are resistant and resilient to disturbance. Between 16 and 25% of the intercepted rainfall is channelized to deep soil storage by stemflow and root channelization. Stemflow water is nutrient enriched and contributes to the  &quot;islands of fertility&quot; that develop under desert shrubs. Drought and rainfall augmentation experiments during the growing season after 5 consecutive years of summer drought found that (1) growth of creosotebushes, , was not significantly affected, (2) perennial grasses and forbs disappeared on droughted plots, (3) nitrogen mineralization increased in the short term, and (4) densities and biomass of spring annual plants increased on the droughted plots. Doubling summer rainfall for 5 consecutive years had less-significant effects. Coppice dunes treated with herbicide in 1979 to kill mesquite () had the same frequency of occurrence of the shrub as the untreated dunes when remeasured in 1993. These data indicate that the shrub-dominated ecosystems persist because they are resistant and resilient to climatic and anthropogenic stresses.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1995-91471</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Nash, M. H.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Subterranean termites:  regulators of soil organic matter in the Chihuahuan Desert</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1995</style></year></dates><volume><style face="normal" font="default" size="100%">19</style></volume><pages><style face="normal" font="default" size="100%">15-18</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Soil organic matter and the abundance of subterranean termites were measured at 89 locations spaced at 30-m intervals from the bottom to the top of a small desert watershed.  There was no correlation between soil organic matter content and topographic position on the watershed.  Analysis by autocorrelogram demonstrated that the soil organic matter content was randomly distributed on the watershed.  There was a highly significant negative correlation between termite abundance and soil organic matter, r = -0.97.  Soils characterized by horizon in soil pits within each vegetation type (soil type) showed some relationships to erosion-deposition areas on the watershed, with surface organic matter contents varying between 3.4% in the playa basin where termites were absent to 0.4% in a sparse shrubland on erosional soils.  In the northern Chihuahuan Desert, subterranean termites appear to be responsible for most of the variation in soil organic matter.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1995-91479</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">DiMarco, R.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Variability in soils and vegetation associated with harvester ant (&lt;i&gt;Pogonomyrmex rugosus&lt;/i&gt;) nests on a Chihuahuan Desert watershed</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1995</style></year></dates><volume><style face="normal" font="default" size="100%">20</style></volume><pages><style face="normal" font="default" size="100%">169-173</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><accession-num><style face="normal" font="default" size="100%">LTER.1995-91482</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Kerley, G. I. H.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Desert dwelling small mammals as granivores: intercontinental variations</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1994</style></year></dates><volume><style face="normal" font="default" size="100%">42</style></volume><pages><style face="normal" font="default" size="100%">543-555</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><accession-num><style face="normal" font="default" size="100%">LTER.1994-91490</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Franco, A. C.</style></author><author><style face="normal" font="default" size="100%">de Soyza, A. G.</style></author><author><style face="normal" font="default" size="100%">Virginia, R. A.</style></author><author><style face="normal" font="default" size="100%">Reynolds, J. F.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Effects of plant size and water relations on gas exchange and growth of the desert shrub &lt;i&gt;Larrea tridentata&lt;/i&gt;</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1994</style></year></dates><volume><style face="normal" font="default" size="100%">97</style></volume><pages><style face="normal" font="default" size="100%">171-178</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">&lt;i&gt;Larrea tridentata &lt;/i&gt;is a xerophytic evergreen shrub, dominant in the arid regions of the southwestern United States.  We examined relationships between gas-exchange characteristics, plant and soil water relations, and growth responses of large versus small shrubs of &lt;i&gt;L. tridentata&lt;/i&gt; over the course of a summer growing season in the Chihuahuan Desert of southern New Mexico, USA.  The soil wetting front did not reach 0.6 m, and soils at depth of 0.6 and 0.9 m remained dry throughout the summer, suggesting that &lt;i&gt;L. tridentata&lt;/i&gt; extracts water largely from soil near the surface.  Surface soil layers (&lt;0.3 m) were drier under large plants, but pre-dawn xylem water potentials were similar for both plant sizes suggesting some access to deeper soil moisture reserves by large plants.  Stem elongation rates were about 40% less in large, reproductively active shrubs than in small, repoductively inactive shrubs.  Maximal net photosynthetic rates (Pmax) occurred in early summer (21.3 u mol m-2 s -1), when pre-dawn xylem water potential (XWP) reached ca. -1MPa.  Although both shrub sizes exhibited similar responses to environmental factors, small shrubs recovered faster from short-term drought, when pre-dawn XWP reached about -4.5 MPa and Pmax decreased to only ca. 20% of unstressed levels.  Gas exchange measurements yielded a strong relationship between stomatal conductance and photosynthesis, and the relationship between leaf-to-air vapor pressure deficit and stomatal conductance was found to be influenced by pre-dawn XWP.  Our results indicate that stomatal repsonses to water stress and vapor pressure deficit are important in dtermining rates of carbon gain and water loss in &lt;i&gt;L. tridentata&lt;/i&gt;.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1994-91495</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">MacKay, W. P.</style></author><author><style face="normal" font="default" size="100%">Loring, SJ</style></author><author><style face="normal" font="default" size="100%">Zak,  J.C.</style></author><author><style face="normal" font="default" size="100%">Silva, S. I.</style></author><author><style face="normal" font="default" size="100%">Fisher, F. M.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Factors affecting loss in mass of creosotebush leaf-litter on the soil surface in the northern Chihuahuan Desert</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1994</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://www.jstor.org/stable/3672197</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">39</style></volume><pages><style face="normal" font="default" size="100%">78-82</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We examined the relative importance of biotic factors (microarthropods, termites, and fungi), and abiotic weathering on loss in mass of creosotebush leaf-litter on the soil surface in the northern Chihuahuan Desert. We treated litter with either an insecticide (chlordane), a fungicide (benomyl), a general biocide (HgCl&lt;sub&gt;2&lt;/sub&gt;-CuSO&lt;sub&gt;4&lt;/sub&gt; solution or, as a control, distilled water. Our results suggest that microarthropods and fungi do not play significant roles in creosotebush litter decomposition in arid habitats. The rate of loss in mass from fungicide treated litter was not significantly different from control litter. Litter in fungicide treatment plots differed from that of the abiotic treatment plots in having higher rates of loss, suggesting that other components of the litter communities compensate for the lack of certain organismal groups. The rate of loss in litter treated with the general biocide during late summer was not significantly different from the rates for other litter, demonstrating that abiotic factors have an important effect. We suggest that these factors include intense sunlight and high UV-radiation and heat of the soil surface in summer. Actual evapotranspiration and decomposition rates of surface litter are uncorrelated in desert ecosystems. This may be due to abiotic fragmentation of the litter and the necessity of a threshold (amount or intensity) of rainfall which is necessary to fragment litter and wash it into the soil.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1994-91496</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">James, Craig D.</style></author><author><style face="normal" font="default" size="100%">Hoffman, M. Timm</style></author><author><style face="normal" font="default" size="100%">Lightfoot, David C.</style></author><author><style face="normal" font="default" size="100%">Forbes, Gregory S.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Fruit abortion in Yucca elata and its implications for the mutualistic association with yucca moths</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1994</style></year></dates><volume><style face="normal" font="default" size="100%">69</style></volume><pages><style face="normal" font="default" size="100%">207-216</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The yucca moth &lt;i&gt;Tegeticula yuccasella&lt;/i&gt; is the sole pollinator of &lt;i&gt;Yucca elata&lt;/i&gt;, and relies on yucca fruits to complete its life cycle.  A high percentage of pollinated flowers abort, killing the &lt;i&gt;T. yuccasella&lt;/i&gt; eggs and larvae in them.  We examined patterns of fruit production and abortion in &lt;i&gt;Y. elata&lt;/i&gt;, and related these patterns to vegetative characteristics, moth abundance, and environmental conditions.  We studied 38 inflorescences throughout their flowering period, during one season in southern New Mexico, USA.  Each night we recorded the number of flowers opening, the number of fruit formed, the relative abundance of yucca moths, and climatic conditions.  We monitored 11,786 flowers, resulting in 699 mature fruit.  Large inforescences produced more, but proportionately fewer fruit than small inflorescences.  Inflorescences flowering late in the season produced proportionately more fruit than inflorescences flowering early.  Only 6.6% (extremes 1.4-15.1%) of flowers produced mature fruits.  Hand-pollination of all flowers on inflorescences did not significantly increase the proportion of flowers that developed into mature fruit.  Fruit production appeared to be resource-, not pollinator- limited.  Ninety per cent of observed moth-pollinated flowers aborted (N=31), resulting in the death of moth eggs and larvae laid in the flowers.  Neither yucca moth abundance or climatic conditions correlated with fruit production.  Inflorescences usually developed mature fruit from flowers opening during a &quot;window&quot; of consecutive nights, lasting for five nights on average (36% of the flowering period of an inflorescence).  The timing of the window of fruit production was highly variable and unpredictable: mature fruits were produced from flowers opening at the beginning, in the middle, or at the end of the flowering period of an inflorescence.  The results for &lt;i&gt;Y. elata&lt;/i&gt; do not support existing hypotheses that attempt to explain patterns of selective fruit production.  High rate of abortion of initiated fruit, and the apparently unpredictable pattern of fruit production by individual inflorescences, may stabilize the mutualistic interaction by preventing yucca moths from hyper-ovipositing flowers that have a high probability of developing into mature fruits.  A risk-spreading strategy of oviposition is likely to be more successful for the moth than multiple ovipositions per flower.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1994-91498</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Kerley, G. I. H.</style></author><author><style face="normal" font="default" size="100%">Tiver, F.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Herbivory of clonal populations: cattle browsing affects reproduction and population structure of &lt;i&gt;Yucca elata&lt;/i&gt;</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1993</style></year></dates><volume><style face="normal" font="default" size="100%">93</style></volume><pages><style face="normal" font="default" size="100%">12-17</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">//NMSU, USDA//LTER II//Listed in LTER3 proposal as citing LTER2 support//</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1993-91539</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">James, Craig D.</style></author><author><style face="normal" font="default" size="100%">Hoffman, M. Timm</style></author><author><style face="normal" font="default" size="100%">Lightfoot, David C.</style></author><author><style face="normal" font="default" size="100%">Forbes, Gregory S.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Pollination ecology of &lt;i&gt;Yucca elata&lt;/i&gt;:  an experimental study of a mutualistic association</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1993</style></year></dates><volume><style face="normal" font="default" size="100%">93</style></volume><pages><style face="normal" font="default" size="100%">512-517</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The pollination biology of a population of 250 &lt;i&gt;Yucca elata&lt;/i&gt; and the prodoxid yucca moth &lt;i&gt;Tegeticula yuccasella&lt;/i&gt; have a mutualistic association that is essential for the successful sexual reproduction of both species.  However, a wide range of other invertebrate species visit flowers during the day and at night.  Our aim was to quantify the role of yucca moths and other invertebrate visitors in pollination and fruit set, using manipulative field experiments.  Inflorescences were bagged during the day or night (&lt;i&gt;N&lt;/i&gt;= 12 Inflorescences) to restrict flower visitors to either nocturnal or diuranl groups.  Yucca moths were active exclusively nocturnally during the flowering period and thus did not visit Inflorescences that were unbagged during the day.  None of the 4022 flowers exposed only to diurnal visitors set fruit, whereas 4.6% of the 4974 flowers exposed only to nocturnal visitors (including yucca moths) produced mature fruit.  The proportion of flowers production fruit in the latter treatment was not significantly different from unbagged control Inflorescences.  In a series of experimental manipulations we also determined that:  (1) flowers opened at dusk and were open for tow days on average, but were only receptive to pollen on the first night of opening; (2) pollen must be pushed down the stigmatic tube to affect pollination; and (3) most plants require out-cross pollination to produce fruit.  The combination of these results strongly suggests that yucca moths are the only species affecting pollination in &lt;i&gt;Y. elata&lt;/i&gt; and that if another species was to affect pollination, it would be a rare event.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1993-91546</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Hoffman, M. T.</style></author><author><style face="normal" font="default" size="100%">James, C. D.</style></author><author><style face="normal" font="default" size="100%">Kerley, G. I. H.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Rabbit herbivory and its effect on cladode, flower, and fruit production of Opuntia violacea var macrocentra (Cactaceae) in the northern Chihuahuan Desert, New Mexico</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1993</style></year></dates><volume><style face="normal" font="default" size="100%">38</style></volume><pages><style face="normal" font="default" size="100%">309-315</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We studied the timing and effect of black-tailed jackrabbit and desert cottontail herbivory on a platyopuntia species, Opuntia violacea var macrocentra at a site on the Jornada del Muerto, 35 km north of Las Cruces, New Mexico in the northern Chihuahuan Desert.  Total monthly fecal pellet dry mass collected around the base of individual opuntias over 15 months indicates that both rabbit species exhibit a seasonal preference for this opuntia with the greatest grazing pressure evident during dry seasons or when little annual or new growth of other perennial plants is present.  Neither rabbit species appears to graze small opuntias possessing less than three cladodes.  They also appear to avoid grazing new cladodes, since more than 80% of the cladodes produced in May 1990 survived for six months.  The proportion of individual opuntias grazed increases with increasing cladode number size class as does the mean fecal-pellet dry mass collected around the base of individual opuntias.  Spinescence did not affect grazing intensity over the 15-month study period.  Instead, plant size and grazing history appear to be the most important determinants of grazing intensity.  Although statistically not significant, there is a trend on our data which suggests that above-average rabbit hebivory may negatively affect cladode, flower and fruit production in intermediate opuntia size-classes only.  For individuals with either very few or very many cladodes these parameters appear unaffected by rabbit herbivory.  However, the strongly-skewed size-class frequency distribution indicates that recruitment of juvenile opuntias into the population is little affected by rabbit herbivory.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1993-91548</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>6</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors><secondary-authors><author><style face="normal" font="default" size="100%">O'Brien, R. J. (eds.)</style></author></secondary-authors></contributors><titles><title><style face="normal" font="default" size="100%">Biogeochemical consequences of desertification</style></title><secondary-title><style face="normal" font="default" size="100%">The Science of Global Change, The Impact of Human Activities on the Environment</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1992</style></year></dates><publisher><style face="normal" font="default" size="100%">American Chemical Society</style></publisher><pub-location><style face="normal" font="default" size="100%">Washington, D. C.</style></pub-location><pages><style face="normal" font="default" size="100%">352-359</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Processes that reduce the productivity of arid and semi-arid lands, collectively known as desertification, affect more than 3 billion hectares or more than 80% of such lands.  The degradation process results in redistribution of water and nutrients, loss of find soil fractions and replacement of palatable plants with undesirable plants.  These changes frequently uncouple rainfall and productivity on a temporal scale.  This uncoupling is probably due to modification of the nitrogen cycle as a result of the desertification processes.  Changes in vegetation can produce changes in fluxes of radiatively active gasses and a variety of organic volatiles to the atmosphere.  Redistribution of soil water may produce &quot;hot&quot; spots for denitrification and for ammonia volatilization that differ in extent both spatially and temporally from undesertified ecosystems.  Dust from desertified areas can modify the chemistry of rainfall in areas distant from the dust source.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1992-91567</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Ludwig, John A.</style></author><author><style face="normal" font="default" size="100%">Noble, James C.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">The importance of subterranean termites in semi-arid ecosystems in south-eastern Australia</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1992</style></year></dates><volume><style face="normal" font="default" size="100%">22</style></volume><pages><style face="normal" font="default" size="100%">87-91</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">In mulga, &lt;i&gt;Acacia aneura&lt;/i&gt;, woodland in north-western New South Wales, Australia, subterranean termites, constructed foraging galleries over organic debris, litter fragments, litter trains, dead wood, dead grass in perennial grass clumps and kangaroo and sheep dung.  The larger quantities of litter, litter trains and dead wood in the mulga groves resulted in higher cover of termite gallery sheeting in this habitat, 6.56+-1.02%, than in the intergrove erosion slopes, 2.2.8+-0.32%.  In the upper 20 cm of soil there were 52.1 storage galleries m-2.  In mallee-spinifex habitats in south-western New South Wales, there was no evidence of subterranean termite feeding on dung or the dead stems of spinifex grass, &lt;i&gt;Triodia iritans&lt;/i&gt;, but dead stems of mallee, &lt;i&gt;Eucalyptus&lt;/i&gt; spp. were galleried and etched by termites.  The numbers of sub-surface termite storage galleries in this habitat averaged 137.5 m-2.  These galleries ranged between 4.5 and 49.0 cm3.  These data suggest that subterranean termites in these Australian ecosystems may be more important as detritivores and in their effects on hydrological properties of soil than has been documented for subterranean termites in the Chihuahuan Desert of North America.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1992-91585</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">MacKay, William P.</style></author><author><style face="normal" font="default" size="100%">Zak,  John C.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Litter decomposition in Chihuahuan Desert playa</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1992</style></year></dates><volume><style face="normal" font="default" size="100%">128</style></volume><pages><style face="normal" font="default" size="100%">84-94</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><accession-num><style face="normal" font="default" size="100%">LTER.1992-91587</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Chew, Robert M.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">A long-term positive effect of kangaroo rats (&lt;i&gt;Dipodomys spectabilis&lt;/i&gt;) on creosotebushes (&lt;i&gt;Larrea tridentata&lt;/i&gt;)</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1992</style></year></dates><volume><style face="normal" font="default" size="100%">22</style></volume><pages><style face="normal" font="default" size="100%">375-386</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Several studies have shown the effects of the mounds of the banner-tailed kangaroo rat (&lt;i&gt;Dipodomys spectabilis&lt;/i&gt; Merriam) on desert annuals.  There can be effects on density, biomass and composition of the herbaceous assemblage (Moroka et al., 1982; Mun &amp; Whitford, 1989).  As a result of a long-term study of a site in south-eastern Arizona, we observed a positive effect of these mounds on the growth, flowering and fruiting, and survival of creosotebush, which is the dominant woody perennial of the community.  This effect became obvious at this site long after the kangaroo rats disapppeared from the system, probably as a result of invasion of creosotebushes and other shrubby vegetaion into what was previously a desert grassland system.  Whereas creosotebushes had a negative effect on the kangaroo rat population, the mounds created by these rodents have had a residual positive effect on the creosotebushes. A number of measurements were made to examine the nature of this unusual, if not unique, relationship, and to provide some basis for speculation as to the cause(s) of the positive effect.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1992-91588</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Virginia, R. A.</style></author><author><style face="normal" font="default" size="100%">Jarrell, W. M.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Freckman, DW</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Soil biota and soil properties associated with surface rooting zone of mesquite (&lt;i&gt;Prosopis glandulosa&lt;/i&gt;) in historical and recently desertified Chihuahuan Desert habitats</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1992</style></year></dates><volume><style face="normal" font="default" size="100%">14</style></volume><pages><style face="normal" font="default" size="100%">90-98</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The woody legume, mesquite (&lt;i&gt;Prosopis glandulosa&lt;/i&gt;), has expanded from its historical habitats (playas and arroyos) to recently occupied grassland and dune habitats during the desertification of perennial grasslands in the Chihuahuan Desert.  We studied historical and recently occupied sites, having hypothesized that the trophic structure and population density of soil microarthropods and nematodes associated with the surface root system of mesquite would differ in sites representing historical and recent habitats, and that the N mineralization potential would be lower in the recent habitats.  Our results showed that net N mineralization potential did not differ significantly among the sites, even though soil nutrient concentrations and texture varied widely.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1992-91598</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Carlson, S. R.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Ant mound influence on vegetation and soils in a semiarid mountain ecosystem</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1991</style></year></dates><volume><style face="normal" font="default" size="100%">126</style></volume><pages><style face="normal" font="default" size="100%">125-139</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We examined vegetation patterns and soil properties associated with western harvester (&lt;i&gt;Pogonomyrmex occidentalis&lt;/i&gt;) mounds in a pinyon-juniper community and a ponderosa pine community near Los Alamos, New Mexico.  Plant-clearing habits of the ants exerted a minor influence on total plant cover.  Denuded zones (discs) around the mounds in the pinyon-juniper and ponderosa pine sites represented 1.2% and 1.0% of the total surface area and reduced plant cover 0.35% and 0.49%, respectively.  Vegetation near the perimeter of the cleared discs had decreased species richness and lowered percent cover compared with adjacent reference areas (sampled 3.0 m from discs).  Comparisons of plant species occurrences around the discs revealed that (1) most species, including dominant understory plants, were evenly dispersed in relation to nest discs; (2) two species - one in each site - were significantly associated with areas near discs; and (3) six species - four in the pinyon-juniper site and two in the ponderosa pine site - were significantly associated with reference areas.  Analysis of vegetation on abandoned mounds suggested that seed predation by the ants influences patterns of plant species occurrence adjacent to nests.  Active mounds in the pinyon-juniper and ponderosa pine sites occured at densities of 17/ha and 14/ha and had an average mass of 38 kg and 48 kg, respectively.  Particle size analysis indicated that the ants construct mounds primarily of gravel and sand fractions.  Mound soils at both sites had elevated concentrations of NO3, P and K, increased conductivity and lower water content compared with disc and reference soils.  Disc soils in both sites had lower organic matter content but were otherwise similar to reference soils.  Activities of P. occidentalis cause localized accumulations of nutrients that are unavailable to plants until mound abandonment.  Colony influences on vegetation patterns beyond the denuded discs and lingering effects of abondoned mounds contribute to plant community heterogeneity.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1991-91606</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Steinberger, Y.</style></author><author><style face="normal" font="default" size="100%">Aldon, Earl F.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Ground-dwelling arthropods of the Rio Puerco Watershed, New Mexico</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1991</style></year></dates><volume><style face="normal" font="default" size="100%">5</style></volume><pages><style face="normal" font="default" size="100%">147-153</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">One of the most important components of a terrestrial ecosystem is the ground-dwelling arthropods, which play a functional role as general detritivores and predators. Because of their sensitivity to rangeland deterioration, a study on the abundance of the ground-dwelling arthropods was undertaken in four different habitats of the Rio Puerco Watershed in New Mexico.  Thirty-two traps (768 trap nights) were place in each of four habitats: grama grassland, sagebrush, shrubland, juniper grassland, and pine woodland.  There were more general of ants in the juniper grassland habitat than in the other habitats.  Fieldcrickets, &lt;i&gt;Gryllus&lt;/i&gt; sp., were most abundant in the grama grassland and entomobryid collembolans were most abundant in juniper grassland and pine woodland habitats.  Despite difference in species composition, the ground-dwelling arthropod fauna was dominated by detrivouous forms in every habitat.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1991-91629</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Lightfoot, D. C.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Productivity of creosotebush foliage and associated canopy arthropods along a desert roadside</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1991</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://www.jstor.org/sici?sici=0003-0031(1991)125%3A2%3C310%3APOCFAACAAADR%3E2.0.CO%3B2-O&amp;origin=serialsolutions</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">125</style></volume><pages><style face="normal" font="default" size="100%">310-322</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">A sampling study was designed to test the hypothesis that creosotebush &lt;i&gt;(Larrea tridentata) &lt;/i&gt;shrubs along a roadside were larger, more vigorous and supported greater populations of foliage arthropods than shrubs growing 20 m away from the road margin.  Structural and chemical attributes of shrubs and associated foliage arthropods were measured.  Roadside shrubs were larger, had denser foliage, more flowers, higher foliar nitrogen contents and lower foliar resin contents than shrubs growing away from the road. Foliage arthropod densities were significantly higher on roadside shrubs. Sap-feeding herbivores dominated numerically and accounted for most of the differences in arthropod abundances between roadside and nonroadside shrubs. Numbers of foliage arthropods were positively correlated with shrub size, density and foliar nitrogen contents, and negatively correlated with foliar resin contents. These findings, in concordance with other studies, indicate that in arid environments productive, vigorous plants are preferred hosts for herbivorous insects.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1991-91641</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Subterranean termites and long-term productivity of desert rangelands</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1991</style></year></dates><volume><style face="normal" font="default" size="100%">19</style></volume><pages><style face="normal" font="default" size="100%">235-243</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Studies of soil properties, growth and species composition of vegetation, hydrology and patterns of organic matter removal were made on plots where termites had been eliminated and on plots with subterranean termites present.  Subterranean termites affected all of the parameters measured.  There was a negative correlation between termite abundance/activity and soil organic matter.  Soils of termite free plots have lower infiltration and water storage but higher soil nitrogen.  These soil properties have an effect on the species composition and productivity vegetation.  The importance of subterranean termites as effectors of soil properties and vegetation suggests that these animals are key consumers in desert rangelands.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1991-91648</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Schlesinger, W.H.</style></author><author><style face="normal" font="default" size="100%">Reynolds, J. F.</style></author><author><style face="normal" font="default" size="100%">Cunningham, G.L.</style></author><author><style face="normal" font="default" size="100%">Huenneke, L.F.</style></author><author><style face="normal" font="default" size="100%">Jarrell, W. M.</style></author><author><style face="normal" font="default" size="100%">Virginia, R. A.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Biological Feedbacks in Global Desertification</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1990</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http:usda-ars.nmsu.edu/biblio/pdf/111.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">247</style></volume><pages><style face="normal" font="default" size="100%">1043-1048</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Studies of ecosystem processes on the Jornada Experimental Range in southern New Mexico suggest that long-term grazing of semiarid grasslands leads to an increase in the spatial and temporal heterogeneity of water, nitrogen, and other soil resources. Heterogeneity of soil resources promotes invasion by desert shrubs, which leads to a further localization of soil resources under shrub canopies. In the barren area between shrubs, soil fertility is lost by erosion and gaseous emissions. This positive feedback leads to the desertification of formerly productive land in southern New Mexico and in other regions, such as the Sahel. Future desertification is likely to be exacerbated by global climate warming and to cause significant changes in global biogeochemical cycles.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1990-91658</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Fisher, F. M.</style></author><author><style face="normal" font="default" size="100%">Freckman, DW</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Decomposition and soil nitrogen availability in Chihuahuan Desert field microcosms</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1990</style></year></dates><volume><style face="normal" font="default" size="100%">22</style></volume><pages><style face="normal" font="default" size="100%">241-249</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We examined the relationship between the decomposition of seven litter and root substrates, soil N availability, and populations of soil biota in field microcosm for 13 months.  Most of the variation of N loss from the substrates was a function of initial substrate N concentration.  Small portions of the variation of substrate mass loss and soil inorganic N were explained by initial substrate N concentration.  Most of the variation of substrate mass losss, soil inorganic N, and soil biota populations was explained by differences between the decomposition of roots vs litter and of annual roots vs perennial roots.  N loss from roots was more rapid than from litter.  Mass of bacteria plus yeast in root microcosms was lower, nematode populations were higher, and the potential N mineralization rate at 9 months was higher than in litter microcosms.  These results suggest that organic matter turnover in root microcosms was more rapid than in litter microcosms.  Mass loss from annual roots was higher but N loss was lower than from perennial roots.  Bacteria plus yeast mass in annual-root microcosms was lower, nematode populations were higher, and soil inorganic N was less than in perennial-root microcosms.  The addition of annual roots reduced inorganic N concentrations below that of the unamended controls and the other substrate treatment on month 6 and 9 samples indicating that annual-root decomposition led to N immobiliaztion or dentrification.  The addition of litter or perennial-roots increased soil inorganic N concentrations above the unamended control in the month 9 samples.  The decomposition of N-poor annual plant roots may significantly reduce N availability in desert ecosystems.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1990-91663</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Cepeda-Pizarro, Jorge G.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Decomposition patterns of surface leaf litter of six plant species along a Chihuahuan Desert watershed</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1990</style></year></dates><volume><style face="normal" font="default" size="100%">123</style></volume><pages><style face="normal" font="default" size="100%">319-330</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Mass losses from litter bags of surface creosote bush litter placed along a Chihuahuan Desert watershed were measured to answer the following questions:  (1) Do edaphic factors affect organic matter losses?  (2) Are there differences in mass losses between the litter of the site-dominant plant species and creosote bush leaf litter?  We hypothesized that (1) mass losses of all litter types would be higher at the base of the watershed and lower on the upper portions of the watershed and (2) mass losses of the litter of the site-dominant plants would be higher than those of creosote bush leaf litter in the same site.  Mass losses from creosote bush leaf litter did not follow the moisture-organic matter gradient present in the watershed.  Mass losses where higher at mid-slope run-on areas than in upper-slope erosional sites and the dry lake basin.  Mass losses were highest where subterranean termite activity was the highest.  There were differences between losses from the litter of the site-dominant and creosote bush leaf litter in some instances, but these differences were not attributable to differences in lignin content nor C:N ratio.  Mass losses of litter of site-dominant species were not always higher than that of creosote bush leaf litter in the same site.  Mass losses were best described by the double exponential model.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1990-91664</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Mun, Hyeong-Tae</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Factors affecting annual plant assemblages on banner-tailed kangaroo rat mounds</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1990</style></year></dates><volume><style face="normal" font="default" size="100%">18</style></volume><pages><style face="normal" font="default" size="100%">165-173</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We studied patterns of annual plants assemblages and soil properties of banner-tailed kangaroo rat (&lt;i&gt;Dipodomys spectabilis&lt;/i&gt;) mounds.  The spring annual flora on mounds was dominated by &lt;i&gt;Descuraina pinnata&lt;/i&gt; and &lt;i&gt;Eschscholtzia mexicana&lt;/i&gt;; intermound areas were dominated by &lt;i&gt;Eriastrum diffusum&lt;/i&gt;.....  Differences in species composition and biomass production of annual plants between kangaroo rat mounds and intermound areas are attributed to the differences in both soil physical properties and nitrogen availability.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1990-91673</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Lightfoot, David C.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Phytophagous insects enhance nitrogen flux in a desert creosotebush community</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1990</style></year></dates><volume><style face="normal" font="default" size="100%">82</style></volume><pages><style face="normal" font="default" size="100%">18-25</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We tested the hypothesis that herbivorous insects on desert shrubs contribute to short-term nitrogen cycling, and increase rates of nitrogen flux from nutrient rich plants.  Creosotebush (&lt;i&gt;Larrea tridentata&lt;/i&gt;) shrubs were treated with different combinations of fertilizer and water augmentations, resulting in different levels of foliage production and foliar nitrogen contents.  Foliage arthropod populations, and nitrogen in canopy dry throughfall, wet throughfall and stemflow were measured to assess nitrogen flux rates relative to arthropod abundances on manipulated and unmanipulated shrubs over a one-month period during peak productivity.  Numbers and biomass of foliage arthropods were significantly higher on fertilized shrubs.  Sap-sucking phytophagous insects accounted for the greatest numbers of foliage arthropods, but leaf-chewing phytophagous insects represented the greatest biomass of foliage arthropods.  Measured amounts of bulk frass (from leaf-chewing insects) were not significantly different among the various treatments.  Amounts of nitrogen from dry and wet throughfall and stemflow were significantly greater under fertilized shrubs due to fine frass input from sap-sucking insects.  Increased numbers and biomass of phytophagous insects on fertilized shrubs increased canopy to soil nitrogen flux due to increased levels of herbivory and excrement.  Nitrogen excreted by foliage arthropods accounted for about 20% of the total one month canopy to soil nitrogen flux, while leaf litter accounted fro about 80%.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1990-91683</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">MacKay, William P.</style></author><author><style face="normal" font="default" size="100%">Loring, Steven J.</style></author><author><style face="normal" font="default" size="100%">Frost, Thomas M.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Population dynamics of a playa community in the Chihuahuan Desert</style></title><secondary-title><style face="normal" font="default" size="100%">The Southwestern Naturalist</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">NTL</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1990</style></year></dates><volume><style face="normal" font="default" size="100%">35</style></volume><pages><style face="normal" font="default" size="100%">393-402</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><issue><style face="normal" font="default" size="100%">4</style></issue><accession-num><style face="normal" font="default" size="100%">LTER.1990-69181</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Abiotic controls on the functional structure of soil food webs</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1989</style></year></dates><volume><style face="normal" font="default" size="100%">8</style></volume><pages><style face="normal" font="default" size="100%">1-6</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The hypothesis that the trophic structure of soil food webs changes as a result of the abiotic environment was examined by reviewing studies of soil biota.  In dry soils with a  water potential below -1.5 MPa, most bacteria, protozoans, and many species of nematodes are not active.  These taxa persist in the soil in a state of anhydrobiosis.  Because soil fungi grow at soil water potentials of -6.0 to -8.0 MPa, soil food webs in dry environments appear to be fungal-based and fungal grazers in dry environments appear to be predominantly fungiphagous mites.  There is indirect evidence that some species of fungiphagous mites remain inactive in dry soils in a state of &quot;crytobiosis&quot;.  In habitats where there is insufficient vegetative cover to shade and modify the soil surface, the functional soil food web consists of fungi and a few taxa of soil acari for extended periods of time.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1989-91701</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Parker, Lawrence W.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Contributions of soil fauna to decomposition and mineralization processes in semiarid and arid ecosystems</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1989</style></year></dates><volume><style face="normal" font="default" size="100%">3</style></volume><pages><style face="normal" font="default" size="100%">199-215</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">This review examines the following questions: (1) do soil fauna play an important regulatory role in decomposition and mineralization processes in arid and semiarid ecosystems? (2) if important, what are the mechanisms of the rate regulation, and (3) what are the management implications of these relationships?  Because termites process more than half of the surface litter in hot deserts, this review focuses on faunal effects on buried litter and roots.  Elimination of soil arthropods reduced rates of mass loss and coupled mass loss to soil moisture.  With arthropods present soil moisture accounted for less than 50% of the variation in mass loss.  Other experiments demonstrated that regulation of mass loss results from predatory mites regulating the population density of grazers, thereby preventing overgrazing of the fungi and bacteria.  The regulation of microbial grazers by soil microarthropods also affects rates of mineralization and nutrient immobilization.  Populations of small fungus grazing mites (Tarsonomidae) affect mineralization directly.  Microarthropods tend to uncouple mineralization from abiotic constraints.  Fluctuations in microbial populations and soil fauna are more a function of substrate availability than of abiotic regulation.  Pulses in organic matter inputs result in periods of nutrient immobilization, the extent of which is a function of the rate of recovery of populations of key soil microarthropods.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1989-91710</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Gutierrez, Julio R.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Effect of eliminating subterranean termites on the growth of creosotebush, &lt;i&gt;Larrea tridentata&lt;/i&gt;</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1989</style></year></dates><volume><style face="normal" font="default" size="100%">34</style></volume><pages><style face="normal" font="default" size="100%">549-551</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Soils devoid of termites are more compacted (Elkins et al., 1886), and nitrogen concentrations in the soil surface decrease with depth.  This should affect the growth of deep-rooted shrubs.  We studied the effects of water supplementation and termite removal on shoot growth of the common Chihuahuan Desert shrub &lt;i&gt;Larrea tridentata&lt;/i&gt; to test the hypothesis that reduced infiltration by removal of termites would reduce growth rates of the shrub.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1989-91714</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Lajtha, K.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">The effect of water and nitrogen amendments on photosynthesis, leaf demography, and resource-use efficiency in &lt;i&gt;Larrea tridentata,&lt;/i&gt; a desert evergreen</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1989</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">bibliography/350.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">80</style></volume><pages><style face="normal" font="default" size="100%">341-348</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">In the Chihuahuan Desert of southern New Mexico, both water and nitrogen limit the primary productivity of &lt;i&gt;Larrea tridentata&lt;/i&gt;, a xerophytic avergreen shrub.  Net photosynthesis was positively correlated to leaf N, but only in plants that received supplemental water.  Nutrient-use efficiency, defined as photosynthetic carbon gain per unit N invested in leaf tissue, declined with increasing leaf N.  However, water-use efficiency, defined as the ratio of photosynthesis to transpiration, increased with increasing leaf N, and thus these two measure of resource-use efficiency were inversely correlated  Resorption efficiency was not significantly altered over the nutrient gradient, nor was it affected by irriation treatments.  Leaf longevity decreased significantly with fertilization although the absolute magnitude of this decrease was fairly small, in part due to a large background of insect-induced mortality. Age-specific gas exchange measurements support the hypothesis that leaf aging represents a redistribution of resources, rather than actual deterioration or declining resoruce-use efficiency.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1989-91715</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Mun, H. T.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Effects of nitrogen amendment on annual plants in the Chihuahuan Desert</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1989</style></year></dates><volume><style face="normal" font="default" size="100%">120</style></volume><pages><style face="normal" font="default" size="100%">225-231</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Effects of nitrogen amendments on spring annual plant distribution, primary production, and species diversity in a semi-arid environment were studied.  The ecological responses of spring annual plant species to nitrogen differed between species, and between sites.  The distribution of each species in a control transect was wider than in a nitrogen-treated transect.  Annual plant species diversity at each station in the control transect was higher than that of the nitrogen-treated transect.  The lower site of the Lower Basin Slope areas had the highest species diversity (0.94 for the control and 0.84 for the nitrogen-treated), and the Upper Basin Slope area, shrub vegetation zone, had the lowest species diversity (0.27 for the control and 0.05 for the nitrogen-treated) in both transects.  Inorganic nitrogen in the nitrogen-treated transect soils was consistently higher than that in the control transect soils; however, the former showed more fluctuation from station to station in the latter.  Above-ground biomass of spring annual plants in the nitrogen-treated transect was consistently higher than that in the control at each station.  The maximum above-ground biomass in the control and nitrogen-treated transect was 24.4+-4.4 g m-2 and 61.2+-10.6 g m-2, respectively.  Variations in above-ground biomass along the transect did not parallel with the variation in inorganic nitrogen in soils and species diversity.ty.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1989-91717</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Aldon, Earl F.</style></author><author><style face="normal" font="default" size="100%">Freckman, Diana W.</style></author><author><style face="normal" font="default" size="100%">Steinberger, Yosef</style></author><author><style face="normal" font="default" size="100%">Parker, Lawrence W.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Effects of organic amendments on soil biota on a degraded rangeland</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1989</style></year></dates><volume><style face="normal" font="default" size="100%">42</style></volume><pages><style face="normal" font="default" size="100%">56-60</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Rehabilitation of degraded rangeland requires rebuilding the soil, including soil biota.  In this study wheat straw, bark and wood chips, and dried municipal sludge were placed on native range plots in northcentral New Mexico.     Organic amendments had little or no effects of decomposition of straw, litter respiration, soil respiration, biomass of soil microflora, and populations of most of the soil biota in the second year of the study.  The differences in soil nematode and microarthropod population densities and straw decomposition occurred only in the bark and wood chip mulched plots in year 1.  The absence of differences in year 2 may have been the result of below-average rainfall.  The wood chip bark mulch was visibly present at the end of year 2 but the other mulches were not.  There may be long-term benefits from application of recalcitrant mulches like wood chips and bark, but the less recalcitrant mulching like straw and low application rates of sludge produce no measurable benefit.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1989-91718</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Gutierrez, Julio R.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Effects of water and nitrogen supplementation on phenology, plant size, tissue nitrogen, and seed yield of Chihuahuan Desert annual plants</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1989</style></year></dates><volume><style face="normal" font="default" size="100%">34</style></volume><pages><style face="normal" font="default" size="100%">546-549</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We measured nitrogen content of plant parts, seed yield, and plant mass of four species of spring annual plants grown under different water and soil nitrogen conditions.  We hypothesized that nitrogen would have little effect or a detrimental effect of the nitrogen-fixing legume &lt;i&gt;A. nuttallianus&lt;/i&gt;.  We hypothesized that water would have the greatest effect of the species of annuals that exhibit little or no growth response to soil nitrogen availability (&lt;i&gt;E. diffusum&lt;/i&gt; and &lt;i&gt;E. nuttallianus&lt;/i&gt;).  Plant tissue nitrogen and seed production were hypothesized to increase in the nitrogen fertilizer-responsive species. &lt;i&gt;L. lasiocarpum&lt;/i&gt; and &lt;i&gt;C. stevioides.&lt;/i&gt;</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1989-91719</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Ludwig, John A.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Cornelius, Joe M.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Effects of water, nitrogen and sulfur amendments on cover, density, and size of Chihuahuan Desert ephemerals</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1989</style></year></dates><volume><style face="normal" font="default" size="100%">16</style></volume><pages><style face="normal" font="default" size="100%">35-42</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The generality of the water-limited-nitrogen-regulated plant growth hypothesis for desert ecosystems was tested by applying water, nitrogen and sulfur amendments in a complete factorial design to three Chihuahuan Desert ecosystems.  Water was added every 2 weeks at a rate to about double the long-term annual precipitation average of 225 mm and nitrogen and sulfur were added once in May 1983 (10 g/m2).  Living-canopy area of all herbaceous plants was measured monthly (from April 1983 to December 1984).  Since plants can respond to water and nutrients either by establishing more, but smaller, plants or by growing fewer, but larger, plants, density and plant size were measured (once, in me-April 1984).  Only C3 winter-ephermerals significantly changed in cover, density or plant size in response to the amendments; no significant responses were observed in C4 summer-ephemerals or perennial grasses and forbs.  Species that significantly increased in density did not significantly increase in size and vice versa.  Water tended to limit the number (richness) and density of species, whereas nitrogen regulated plant growth (size).  Sulfur generally reduced soil pH and species density.  This study demonstrated that these general plant responses to increased water and nutrients were highly species and site specific.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1989-91720</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Lightfoot, David C.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Interplant variation in creosotebush foliage characteristics and canopy arthropods</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1989</style></year></dates><volume><style face="normal" font="default" size="100%">81</style></volume><pages><style face="normal" font="default" size="100%">166-175</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We conducted a field study to test the hypothesis that creosotebush (&lt;i&gt;Larrea tridentata&lt;/i&gt;) shrubs growing in naturally nutrient-rich sites had better quality foliage and supported greater populations of foliage arthropods than shrubs growing in nutrient-poor sites.  Nutrient-rich sites had significantly higher concentrations of soil nitrogen than nutrient-poor sites.  Multivariate analysis of variance revealed significant differences between high nutrient and low nutrient shrubs based on a number of structural and chemical characteristics measured.  High nutrient shrubs were larger, had denser foliage, greater foliage production, higher concentrations of foliar nitrogen and water, and lower concentrations of foliar resin than low nutrient shrubs.  Numbers of foliage arthropods, particularly herbivores and predators, were significantly higher on high nutrient shrubs.  Shrub characteristics and foliage arthropod abundances varied considerably from shrub to shrub.  Shrub characteristics representing shrub size, foliage density, foliage growth, and foliar nitrogen and water concentrations were positively correlated with arthropod abundances.  Foliar resin concentrations were negatively correlated with foliage arthropod abundances.  The positive relationship between creosotebush productivity and foliage arthropods is contradictory to the tenet that physiologically stressed plants provide better quality foliage to insect herbivores.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1989-91727</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>6</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Steinberger, Y.</style></author></authors><secondary-authors><author><style face="normal" font="default" size="100%">Willig, M. R. (eds.)</style></author></secondary-authors></contributors><titles><title><style face="normal" font="default" size="100%">The long-term effects of habitat modification on a desert rodent community</style></title><secondary-title><style face="normal" font="default" size="100%">Patterns in the Structure of Mammalian Communities</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1989</style></year></dates><publisher><style face="normal" font="default" size="100%">Special Publications Museum, Texas Tech University</style></publisher><pub-location><style face="normal" font="default" size="100%">Lubbock, Texas</style></pub-location><volume><style face="normal" font="default" size="100%">No. 28</style></volume><pages><style face="normal" font="default" size="100%">33-43</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Data are presented from the results of a 14-year study of changes in composition of a desert rodent community following habitat perturbation.  We studied rodent populations in an area where herbicide treatment reduced shrub cover from 19.7 percent to less than one percent and increased grass cover from 1.3 percent to 22.3 percent. In the first two years following the perturbation, &lt;i&gt;Dipodomys ordii&lt;/i&gt; was the most abundant species in the shrub habitats.  From 1976 through 1984, the rodent community in both areas was dominated by &lt;i&gt;D. merriami&lt;/i&gt; and &lt;i&gt;D. ordii&lt;/i&gt; was absent or occurred at low densities in both habitats.  Species richness was highest in 1976 and 1985 following successive &quot;wet&quot; seasons.  In 1985, following three above average wet seasons, &lt;i&gt;D. ordii&lt;/i&gt; once again became the most abundant rodent in the grass habitat.  &lt;i&gt;Neotoma micropus&lt;/i&gt; increased in abundance with increased grass cover.  These results suggest interspecific competition between &lt;i&gt;D. ordii&lt;/i&gt; and &lt;i&gt;D. merriami&lt;/i&gt; during average to dry periods of limited resources.  Successive wet seasons allow &lt;i&gt;D. ordii&lt;/i&gt;, which has higher fecundity, to increase because resources are not limiting during such periods.  Successive wet seasons result in increased species richness due to immigration of opportunistic species like &lt;i&gt;Sigmodon hispidus&lt;/i&gt; and &lt;i&gt;Reithrodontomys megalotis&lt;/i&gt;.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1989-91729</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Silva, S.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Jarrell, W. M.</style></author><author><style face="normal" font="default" size="100%">Virginia, R. A.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">The microarthropod fauna associated with a deep rooted legume, &lt;i&gt;Prosopis glandulosa&lt;/i&gt;, in the Chihuahuan Desert</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1989</style></year></dates><volume><style face="normal" font="default" size="100%">7</style></volume><pages><style face="normal" font="default" size="100%">330-335</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The rhizosphere microarthropod fauna of a woody, deep-rooted legume, &lt;i&gt;Prosopis glandulosa&lt;/i&gt;, was sampled at four sites in the northern Chihuahuan Desert and compared with the rhizosphere microarthropod fauna of a co-dominant shrub, &lt;i&gt;Larrea tridentata&lt;/i&gt;.  Prostigmatid mites (&lt;i&gt;Speleorchestes&lt;/i&gt; sp., &lt;i&gt;Neognathus&lt;/i&gt; sp., &lt;i&gt;Rhagidia&lt;/i&gt; sp., &lt;i&gt;Tydaeolus&lt;/i&gt; sp., &lt;i&gt;Steneotarsonemus&lt;/i&gt; sp., &lt;i&gt;Tarsonemus&lt;/i&gt; sp., &lt;i&gt;Nanorchestes&lt;/i&gt; sp., &lt;i&gt;Gordialycus&lt;/i&gt; sp.), the cryptostigmatid mites (&lt;i&gt;Bankisonoma ovata&lt;/i&gt; and &lt;i&gt;Passalozetes neomexicanus&lt;/i&gt;), the mesostigmatid (&lt;i&gt;Protogamasellus mica&lt;/i&gt;), and the collembolan (&lt;i&gt;Brachystomella arida&lt;/i&gt;) characterized the fauna at depth greater than 1 m.  Microarthropods were recovered from soils at a depth of 13 m at the edge of a dry lake and at depths of 7 m in a dry wash which were pre-European man &lt;i&gt;P. glandulosa&lt;/i&gt; habitats.  In habitats where  &lt;i&gt;P. glandulosa&lt;/i&gt; is a recent invader, root depth and microarthropods were less than 3 m.  In most habitats, population densities of microarthropods at depth &lt;0.5 m were more than 100 times those at depths &gt;0.5 m.  Population densities of microarthropods associated with  &lt;i&gt;P. glandulosa&lt;/i&gt; growing at the edge of a dry wash were not significantly smaller at 0.5-1.0 m depth than at 0-0.5 m.  The deep-rhizosphere microarthropod fauna is a reduced subset of the fauna of surficial soils, suggesting that this fauna plays a role in decomposition and mineralization processes functionally similar to that of microarthropods in surficial soils.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1989-91732</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>6</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">MacKay, William P.</style></author><author><style face="normal" font="default" size="100%">Zak,  John C.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors><secondary-authors><author><style face="normal" font="default" size="100%">Schmidt, Justin O. (ed.)</style></author></secondary-authors></contributors><titles><title><style face="normal" font="default" size="100%">The natural history and role of subterranean termites in the northern Chihuahuan Desert</style></title><secondary-title><style face="normal" font="default" size="100%">Special Biotic Relationships in the Arid Southwest</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1989</style></year></dates><publisher><style face="normal" font="default" size="100%">University of New Mexico Press</style></publisher><pub-location><style face="normal" font="default" size="100%">Albuquerque, New Mexico</style></pub-location><pages><style face="normal" font="default" size="100%">53-77</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">In this chapter, we summarize what is known about &lt;i&gt;Gnathamitermes tubiformans&lt;/i&gt; include discussions on (1) population estimates, (2) diurnal and seasonal aboveground activity patterns, (3) aboveground gallery construction, (4) their importance in nitrogen cycling and the breakdown of organic matter, (5) interactions with microarthropods, (6) effects on soil infiltration rates, and (7) effects on plant communities.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1989-91733</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Cepeda, Jorge G.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">The relationship between abiotic factors and the abundance patterns of soil microarthropods on a desert watershed</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1989</style></year></dates><volume><style face="normal" font="default" size="100%">33</style></volume><pages><style face="normal" font="default" size="100%">79-86</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">A number of authors have reported the influence of abiotic parameters on the spatial and temporal distribution of soil microarthropods (REDDY, 1984; MALLOW et al., 1984; STREIT, 1982; ANDERSON &amp; HALL, 1977; USHER, 1976).  It is clear from these studies that microarthropods respond differentially to the environmental factors.  USHER (1976) and USHER et al.(1982) stressed the importance of the distributuion of food resources and soul moisture.  SCHENKER (1984), working in a mixed deciduous forest soil, found few statisically significant correlations; although the relations between microarthropods and soil features seemed apparent.  In deserts, the abiotic effects of climatic extremes of soil moisture and temperature are believed to drive many biotical processes taking place in the soil system (WALLWORK, 1982).  The effect of these variables and organic matter on desert soil microfauna has been studied in different ways.  SANTOS et al. (1987) reported highly significant correlations between mass of surface litter and density of microarthropods.  STEINBERGER &amp; WHITFORD (1985) found correlations between total microarthropods and soil moisture but the the significance of these correlations depended upon site and season.  Surveying a desert swale, STEINBERGER &amp; WHITFORD (1985) observed that, whereas overall microarthropod abundance was correlated with soil moisture, some species-populations were not.  WALLWORK et al.(1984), working with simulated rainfall, showed that a continuous irrigation regime caused changes in the reproductive patterns of some species of oribatids, but not in others.  WHITFORD et al. (1981) observed an increase in numbers and diversity of microarthropods in surface litter within one hour after artificial wetting; nevertheless, a subsequent decrease followed in the still moist litter.  STEINBEGER et al. (1984) concluded that water, in the absence of an adequate supply of organic matter, does not stimulate population increase of the soil fauna.  MCKAY et al. (1986) showed that soil temperature (or insolation) has a greater effect on overall microarthropod population densities than soil moisture.  Thus most studies in deserts have focused on climatic variables and only marginally on soil properties.  This study was designed to examine the relationships between abundance patterns of soil microarthropods and soil properties and climate in a northerm Chihuahuan Desert ecosystem.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1989-91739</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Cepeda-Pizarro, J. G.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Spatial and temporal variability of higher microarthropod taxa along a transect in a northern Chihuahuan Desert watershed</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1989</style></year></dates><volume><style face="normal" font="default" size="100%">33</style></volume><pages><style face="normal" font="default" size="100%">101-111</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Numerous factors affect the abundance and distribution of soil microarthropods (SEASTEDT, 1984; WALLWORK et al., 1982; KAMILL et al., 1985).  Few studies have separated the populations of microarthropods in litter and the mineral soil below the litter (ELKINS et al., 1982) in an attempt to examine factors affecting the species composition and numerical abundance of these organisms.  Surface litter is a more exposed habitat and subject to rapid changes in water availability and thermal stresses, especially in sparsely vegetated arid environments (WHITFORD, 1986).  Mineral soil is a buffered environment but provides only sparse food resources especially in arid environments........  Desert watersheds provide a number of habitats varying in soil type, vegetative cover, soil structure, soil organic matter an litter accumulations.  Thus, studies of microarthropod populations on a watershed over time can provide tests of these hypotheses.  Here we report the studies to test these hypotheses.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1989-91744</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Cepeda-Pizarro, J. G.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Species abundance distribution patterns of microarthropods in surface decomposing leaf-litter and mineral soil on a desert watershed</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1989</style></year></dates><volume><style face="normal" font="default" size="100%">33</style></volume><pages><style face="normal" font="default" size="100%">254-268</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><accession-num><style face="normal" font="default" size="100%">LTER.1989-91746</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Silva, Solange I.</style></author><author><style face="normal" font="default" size="100%">MacKay, William P.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Temporal patterns of microarthropod population densities in fluff grass (&lt;i&gt;Erioneuron pulchellum&lt;/i&gt;) litter:  relationship to subterranean termites</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1989</style></year></dates><volume><style face="normal" font="default" size="100%">33</style></volume><pages><style face="normal" font="default" size="100%">333-338</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">In most of the hot desert areas of North America, fluff grass, &lt;i&gt;Erioneuron pulchellum&lt;/i&gt; is the most common perennial grass in desert shrub habitats.  &lt;i&gt;E. pulchellum&lt;/i&gt; is heavily utilized by subterranean termites (Whitford &lt;i&gt;et al&lt;/i&gt;., 1982).  As part of a study to examine faunal effects on the decomposition of  &lt;i&gt;E. pulchellum&lt;/i&gt; litter (Silva &lt;i&gt;et al&lt;/i&gt;., 1985), we studied the sequence of microarthropod colonization and seasonality of microarthropod populations in  &lt;i&gt;E. pulchellum&lt;/i&gt; litter.  These data provide a useful comparison with data on shrub litter microarthropod fauna and allow an assessment of effects of subterranean termite activity on that fauna.     Experimental studies by Steinberger &lt;i&gt;et al&lt;/i&gt;. (1984) demonstrated that the population densities of microarthropods vary as a function of the quantity of litter.  Whitford &lt;i&gt;et al&lt;/i&gt;. (1982), Silva &lt;i&gt;et al&lt;/i&gt;.(1985) and Whitford &lt;i&gt;et al&lt;/i&gt;.(1988) showed that in the Chihuahuan Desert, subterranean termites remove at least 50% of the annual above ground dry matter production.  Based on these observations we hypothesized that termites could substantially reduce suitable habitat for microarthropods hence competitively reduce population sizes of microarthropods.  Here we report the results of studies designed to test these hypotheses.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1989-91749</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Loring, Steven J.</style></author><author><style face="normal" font="default" size="100%">Weems, Danforth C.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Abundance and diversity of surface-active collembola along a watershed in the northern Chihuahuan Desert</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1988</style></year></dates><volume><style face="normal" font="default" size="100%">119</style></volume><pages><style face="normal" font="default" size="100%">21-30</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Jackknife diversity estimates (n2= inverse Simpson diversity index) for surface-active Collembola were examined along a watershed in the Chihuahuan desert of southern New Mexico.  Chord distance measures indicated low similarity in collembolan species composition among the six sites.  However, assemblages at the top (black grama grassland) and bottom (mesquite fringe of playa) of the gradient were similar to each other, possibly reflecting available soil nitrogen.  There was no significant correlation between Collembola and either weekly or long-term precipitation patterns.  Populations of truly epigeic Collembola appeared unaffected by rainfall but were significantly, though weakly, correlated with long-term temperatures.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1988-91757</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Moorhead, D. L.</style></author><author><style face="normal" font="default" size="100%">Fisher, F. M.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Cover of spring annuals on nitrogen-rich kangaroo rat mounds in a Chihuahuan Desert grassland</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1988</style></year></dates><volume><style face="normal" font="default" size="100%">120</style></volume><pages><style face="normal" font="default" size="100%">443-447</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Species composition and cover of spring annual plant communities on banner-tailed kangaroo rat (&lt;i&gt;Dipodomys spectabilis&lt;/i&gt;) mounds in a northern Chihuahuan Desert grassland differed from those on intermound areas.  After seasons of adequate precipitation, cover of annual plants was greater on mounds than on adjacent areas; dominant species on mounds were those known to increase with nitrogen fertilization.  Soil nitrogen content was consistently higher on mound soils than in intermound soils; however, plant cover on mounds was not different from intermound areas following periods of limited precipitation despite differences in nitrogen levels.  Patterns of species composition and cover of annual plants on kangaroo rat mounds are attributed to differential species responses to water and nutrient availabilities.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1988-91765</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Stinnett, K.</style></author><author><style face="normal" font="default" size="100%">Anderson, J.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Decomposition of roots in a Chihuahuan Desert ecosystem</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1988</style></year></dates><volume><style face="normal" font="default" size="100%">75</style></volume><pages><style face="normal" font="default" size="100%">8-11</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Mass losses of tethered buried roots of two woody shrubs and two herbaceous annuals buried in plots irrigated at 25 mm/moth-1, 6 mm/week-1 and no irrigation were measured.  At the end of 1 year, 10-15% of the mass of the herbaceous annual roots remained and 60% of the mass of woody shrub roots remained.  There were no differences in mass loss attributable to added water.  Rates of mass losses of roots in the Chihuahuan Desert were equal to or higher than those reported from mesic ecosystems.  Roots of woody shrubs had relatively constant C:N ratios through the experiment.  There was significant N immobilization in &lt;i&gt;Baileya multiradiata&lt;/i&gt; roots.  Percent mass loss of grass roots, &lt;i&gt;Erioneuron pulchellum&lt;/i&gt;, and herbaceous annual roots, &lt;i&gt;B. multiradiata&lt;/i&gt;, in plots without termites was 15%.  These data suggest that subterranean termites are responsible for most of the mass loss and mineralization of carbon and nitrogen in dead grass and herbaceous roots in the northern Chihuahuan Desert.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1988-91767</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>6</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Loring, Steven J.</style></author><author><style face="normal" font="default" size="100%">MacKay, William P.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors><secondary-authors><author><style face="normal" font="default" size="100%">Ziebell, C. D. (eds.)</style></author></secondary-authors></contributors><titles><title><style face="normal" font="default" size="100%">Ecology of small desert playas</style></title><secondary-title><style face="normal" font="default" size="100%">Small Water Impoundments in Semi-arid Regions</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1988</style></year></dates><publisher><style face="normal" font="default" size="100%">University of New Mexico Press</style></publisher><pub-location><style face="normal" font="default" size="100%">Albuquerque, New Mexico</style></pub-location><pages><style face="normal" font="default" size="100%">89-113</style></pages><isbn><style face="normal" font="default" size="100%">0826310532; ISBN-13: 9780826310538</style></isbn><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Data from a playa located in New Mexico were compared to earlier data and those from other playas to identify the effects of flooding.  Tests of hydrology and chemistry showed the following: water loss to percolation and evaporation; potassium concentrations were higher than those for sodium; and neither the playa water nor soil had a significant increase in chemical compounds from the drainage area following flooding.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1988-91770</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Gutierrez, Julio R.</style></author><author><style face="normal" font="default" size="100%">Da Silva, Oswaldo A.</style></author><author><style face="normal" font="default" size="100%">Pagani, Maria I.</style></author><author><style face="normal" font="default" size="100%">Weems, Danforth</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Effects of different patterns of supplemental water and nitrogen fertilization on productivity and composition of Chihuahuan Desert annual plants</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1988</style></year></dates><volume><style face="normal" font="default" size="100%">119</style></volume><pages><style face="normal" font="default" size="100%">336-343</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The effects of supplemental water supplied as large events, 25 mm per month, or as frequent small events, 6 mm per week, and available nitrogen on density, aboveground biomass and species composition of an annual plant community were studied in the northern Chihuahuan Desert.  The amendments of water an N had no effect on total annual plant density.  However, supplemental water resulted in increased density of eight species and nitrogen fertilization produced increased densities in nine species.  Total aboveground biomass was higher in the nitrogen fertilized plots; water amendments had no effect on dry matter production and there were no significant water-nitrogen interactions.  Cluster analysis showed that species composition was similar on the fertilized plots and that the plots receiving 25 mm month-1 additional water in a single event differed most from the others.  Species richness was highest in the 6 mm week-2 , unfertilized plots, and lowest in the unwatered-unfertilized plots.  Biomass production of six of the 23 species recorded was significantly increased by nitrogen fertilization and biomass of two species was significantly reduced.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1988-91775</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Effects of harvester ant (Pogonomyrmex rugosus) nests on soils and a spring annual, &lt;i&gt;Erodium texanum&lt;/i&gt;</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1988</style></year></dates><volume><style face="normal" font="default" size="100%">33</style></volume><pages><style face="normal" font="default" size="100%">482-485</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Based on the observations of &lt;i&gt;Erodium texanum&lt;/i&gt; and the literature, I hypothesized that the density and biomass of &lt;i&gt;E. texanum &lt;/i&gt;would be higher around the nest discs of &lt;i&gt;Pogonomyrmex rugosus&lt;/i&gt; because of higher soil nutrient levels.  Elevated soil nutrients at the edges of mounds of seed harvesting ants have been described in other areas.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1988-91776</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Stinnet, K.</style></author><author><style face="normal" font="default" size="100%">Steinberger, Y.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Effects of rainfall supplementation on microarthropods on decomposing roots in the Chihuahuan Desert</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1988</style></year></dates><volume><style face="normal" font="default" size="100%">31</style></volume><pages><style face="normal" font="default" size="100%">147-155</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">As part of a study designed to test the hypothesis that single large quantity rainfall events would result in higher rates of root decomposition than small frequent rainfall events or no supplemental water, we sampled the microarthropods associated with the decomposing roots.  We hypothesized that supplemental water would not only affect the rates of decomposition but would also affect the species composition and biomass of the micrfauna feeding on the microflora on the roots.  We further hypothesized that the successional trends in microarthropod populations observed on buried litter by Santos and Whitford (1981) would be similar on decomposing roots.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1988-91777</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Zak, John</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Interactions among soil biota in desert ecosystems</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1988</style></year></dates><volume><style face="normal" font="default" size="100%">24</style></volume><pages><style face="normal" font="default" size="100%">87-100</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">In desert systems, the availability of soil nitrogen can be the single most limiting factor controlling plant growth during periods of adequate soil moisture.  Decomposition and nitrogen-mineralization rates prior to or during peak periods of plant growth can therefore be critical.  Decomposition rates in deserts are generally high, and are relatively independent of rainfall.  These high rates can be attributed to a combination of abiotic weathering, the types of microflora and microfauna associated with plant litter, and the adaptation of the soil biota to moisture pulses.     The factors controlling litter decomposition and subsequent nitrogen mineralization are dependent upon the location of the organic matter in the habitat.  The breakdown of surface litter occurs primarily through either abiotic weathering or by termite consumption.  Microarthropods do not appear to have any role in the decomposition of surface litter owing to abiotic constraints on activity.  The decomposition of roots, and buried litter, however, has been shown to be dependent on the presence of soil microarthropods.  Microbial-microfaunal activity in the root region of desert plants may also have a significant effect on the short-term cycling of nitrogen in arid systems.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1988-91785</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">The Jornada LTER site</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1988</style></year></dates><volume><style face="normal" font="default" size="100%">3</style></volume><pages><style face="normal" font="default" size="100%">7</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The Jornada LTER has experienced a major change in principle investigators and a modification of program objectives.  In January 1988, four new P.I.'s joined the Jornada team: Dr. William Schlesinger (Duke University); Dr. Wesley Jarrell (University of California-Riverside); Dr. Ross Virginia (San Diego State University); and Dr. Laura Huenneke (New Mexico State University).     The modification of program objectives is a change from focusing on hypotheses built around temporal and spatial variability with work focused on a single watershed to hypotheses built around the concept that desertification has changed a previously uniform distribution of resources to a patchy distribution of resources.  We hypothesize that this shift in distribution of resources has disrupted temporal linkages among ecosystems and ecosystem processes.  In order to address questions concerning desertification processes, we have set up research at several new locations on the Jornada and are working to increase collaborative efforts with the USDA programs at the Jornada.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1988-91787</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">MacKay, William P.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Spatial variability of termite gallery production in Chihuahuan Desert plant communities</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1988</style></year></dates><volume><style face="normal" font="default" size="100%">14</style></volume><pages><style face="normal" font="default" size="100%">281-289</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We compared the production of termite [&lt;i&gt;Gnathamitermes tubiformans&lt;/i&gt; (Buckley)] gallery carton along 2 transects passing through several plant communities in the northern Chihuahuan Desert of New Mexico.  There was significantly more gallery carton produced on a mixed basin slope than on the creosotebush scrub zone or on grassland zones.  Gallery carton had a rapid turnover rate.  When termites were present, production ranged from 1000-5650 kg/ha/yr accounting for nitrogen inputs of 145-830 g/ha/yr.  Our data suggest that subterranean termites are not a nitrogen sink as has been suggested in the literature, and that the inputs and outputs of nitrogen in the termite population are about equal.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1988-91798</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Fisher, F. M.</style></author><author><style face="normal" font="default" size="100%">Zak,  J.C.</style></author><author><style face="normal" font="default" size="100%">Cunningham, G.L.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Water and nitrogen effects on growth and allocation patterns of creosotebush in the northern Chihuahuan Desert</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1988</style></year></dates><volume><style face="normal" font="default" size="100%">41</style></volume><pages><style face="normal" font="default" size="100%">387-391</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">A field experiment using 2 patterns of irrigation and 1 level of nitrogen fertilizer (10 g-N m-2) was conducted in order to discern water and nitrogen interactions that may control production of creosotebush (&lt;i&gt;Larrea tridentata&lt;/i&gt; (D.C.) Cov.).  The 2 patterns of irrigation simulated precipitation from small, frequent events (6 mm water added weekly) or large, infrequent events (25 mm water added monthly).  Understnaing the factors controlling the production of this rangeland shrub may aid in the development of strategies for management.  Vegatative growth occurred mostly during March-May (spring) and August-October (summer-fall).  Fruit production occurred mainly in the spring and root growth ocurred mainly in the summer-fall.  Irrigation increased vegetative growth and decreased fruit produciton.  Responses to irrigation were greater during summer-fall than in the spring.  Small, frequent water additions caused larger increases in vegetative plus fruit growth than did large, infrequent water additions.  Nitrogen fertilization increased the growth of both vegetation and fruit in irrigated and unirrigated plots.  Stem mortality and root growth were not significantly affected by irrigation or nitrogen fertilizer.  These results suggest that creosotebush production is limited by both soil moisture and nitrogen availability and that temporal patterns of rainfall may be as important as total amounts.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1988-91802</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Gutierrez, Julio R.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Chihuahuan Desert annuals: importance of water and nitrogen</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1987</style></year></dates><volume><style face="normal" font="default" size="100%">68</style></volume><pages><style face="normal" font="default" size="100%">2032-2045</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We examined the effects of water supplementation and nitrogen amendment on biomass, cover, and density of annual plants on a termite-free and a termite-present area in the Chihuahuan Desert.  Soil moisture was higher in the termite than in the termite-free plots, and in the watered than in the unwatered plots during the spring and summer.  There were no differences in soil moisture among plots during the winter.  Soil nitrogen was higher in the termite-free than in the termite plots.  There were no differences in total plant biomass produced in termite and termite-free areas.  There were significant differences in relative abundances of species among treatments.  Natural rainfall was sufficient for maximum spring-annual biomass development on all plots except for the termite-free unfertilized, unwatered plots.  there were the direst plots but had high soil nitrogen.  Most of the herbaceous species responded to the water amendments by lengthening growing seasons, increasing density, or increasing biomass.  When there was sufficient water for most of the spring annuals, high soil nitrogen levels favored increased densities and biomasses of &lt;i&gt;Descurainia pinnata&lt;/i&gt; and &lt;i&gt;Lepidium lasiocarpum&lt;/i&gt;.  The absence of C4 summer annuals in the high-nitrogen plots suggests that relatively high soil nitrogen adversely affected the summer annuals.  Termite-free watered plots had higher soil moisture than the termite-unwatered plots, but summer annuals were relatively abundant in the latter.  Water amendments had a greater effect on the species abundances in the termite-free area than in the one with termites.  In the area with termites, nitrogen amendments had a greater effect on species abundances.  Species diversity and richness were affected by site fertility as was species composition.  This study demonstrates that we must understand patterns of soil nitrogen availability and processes affecting nitrogen availability in addition to water availability, in order to understand productivity and species composition of Chihuahuan Desert annual plants.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1987-91819</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">MacKay, William P.</style></author><author><style face="normal" font="default" size="100%">Silva, Solange</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Diurnal activity patterns and vertical migration in desert soil microarthropods</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1987</style></year></dates><volume><style face="normal" font="default" size="100%">30</style></volume><pages><style face="normal" font="default" size="100%">65-71</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The objectives of this research were to test the &quot;migration&quot; and &quot;cryptobiosis&quot; hypotheses and to examine the effect of increased soil moisture and reduced soil temperature on activity patterns of microarthropods in surface litter....     We concluded that the active resident population of soil microarthropods in surface litter accumulations in a desert is a function of time of day, which affects diurnal migrant species, and litter temperature, which affects activity of species that are capable of cryptobiosis.  Physiological studies of species that appear capable of cryptobiosis are needed before we can assess the flexibility that this adaptation allows its possessor with respect to utilization of the rich energy and nutrient sources characteristic of leaf litter accumulations.  This is especially important in deserts where soil organic matter is often less than 1% by mass.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1987-91823</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Freckman, DW</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Steinberger, Y.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Effect of irrigation on nematode population dynamics and activity in desert soils</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1987</style></year></dates><volume><style face="normal" font="default" size="100%">3</style></volume><pages><style face="normal" font="default" size="100%">3-10</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The nematode community in litter and soil was examined for a year in the Chihuahuan desert, before and after supplemental rainfall application.  Proportions of nematode-active or anhydrobiotic forms and population densities were determined for 3 treatments: control (natural rainfall), a single, large (25-mm) monthly irrigation pulse, and 4 smaller (6-mm) irrigations spaced at weekly intervals.  In litter the greatest nematode abundance was in the 6 mm week-1 treatment (48 nematodes 20 g-1 litter).  Bacteriovores and fungivores accounted for approximately 95% of the numbers and biomass in all treatments.  In soil, water amendments had no significant effect (P&lt;0.05) on annual mean densities of total nematodes, fungivores, bacterivores, or omnivore predators.  Phytophage densities were greater on both irrigation treatments, with highest densities (9298 m-2) in the 6 mm week-1 soils, which was 5,9% of the total soil nematode density.  Total densities of individual trophic groups were not significantly different before or after rainfall.  soil nematode densities fluctuated independently with trophic group, month, and season.  Bacterial feeders and omnivore predators were the largest contributor to total nematode density and biomass.  Prior to irrigation, there were no differences in the percentage of anhydrobiotes on the three treatments.  Anhydrobiotes decreased after irrigation in all treatments, and were significantly lower in soils of the larger, monthly irrigation.  Nematodes were inactive (anhydrobiotic) and decoupled from decomposition processes when soil water matric potentials reached -0.4 MPa.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1987-91824</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">MacKay, William P.</style></author><author><style face="normal" font="default" size="100%">Fisher, Fred M.</style></author><author><style face="normal" font="default" size="100%">Silva, Solange</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">The effects of nitrogen, water and sulfur amendments on surface litter decomposition in the Chihuahuan Desert</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1987</style></year></dates><volume><style face="normal" font="default" size="100%">12</style></volume><pages><style face="normal" font="default" size="100%">223-232</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The effects of nitrogen, water and sulfur amendments on the decomposition rates of three types of surface litter in the northern Chihuahuan Desert were evaluated.  The amendments had no effects on the decomposition rates of leaf litter from black grama (&lt;i&gt;Bouteloua eriopoda&lt;/i&gt;) and creosotebush (&lt;i&gt;Larrea tridentata&lt;/i&gt;).  The rate of fluff grass (&lt;i&gt;Erioneuron pulchellum&lt;/i&gt;) litter decomposition was increased by water and decreased by sulfur.  Water affected fluff grass decomposition by increasing terminate (&lt;i&gt;Gnathamitermes tubiformans&lt;/i&gt;) above-ground activity.  Sulfur decreased termite activity.  These data suggest that the decomposer microflora and microfauna of the northern Chihuahuan Desert are more limited by quantity of organic matter than by water and nitrogen.  Hence they do not respond opportunistically to increased availability of such resources.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1987-91827</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Peterson, David K.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Foraging behavior of Uta stansburiana and Cnemidophorus tigris in two different habitats</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1987</style></year></dates><volume><style face="normal" font="default" size="100%">32</style></volume><pages><style face="normal" font="default" size="100%">427-433</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Foraging behavior of &lt;i&gt;Uta stansburiana&lt;/i&gt; and &lt;i&gt;Cnemidophorus tigris&lt;/i&gt; was studied in two different habitats in the Chihuahuan Desert.  One habitat was &quot;natural&quot; Chihuahuan Desert dominated by shrubs.  The other habitat had been modified with herbicide and was dominated by sub-shrubs and grasses.  &lt;i&gt;Uta stansburiana&lt;/i&gt; exhibited no preference for plant species or life forms when foraging in either habitat.  Foraging &lt;i&gt;C. tigris&lt;/i&gt; preferentially used mesquite (&lt;i&gt;Prosopis glandulosa&lt;/i&gt;) and, to a lesser extent, creosotebush (&lt;i&gt;Larrea tridentata&lt;/i&gt;) in the natural habitat.  In the grass dominated habitat, &lt;i&gt;C. tigris&lt;/i&gt; used bush muhly (&lt;i&gt;Muhlenbergis porteri&lt;/i&gt;).  &lt;i&gt;Cnemidophorus tigris&lt;/i&gt; spend more time foraging under plants with large litter accumulations.  Shifts in vegetation from grassland to shrubland appear to favor &lt;i&gt;C. tigris&lt;/i&gt;.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1987-91829</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">MacKay, William P.</style></author><author><style face="normal" font="default" size="100%">Zak,  John C.</style></author><author><style face="normal" font="default" size="100%">Silva, Solagne</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Gnathamitermes tubiformans (Isoptera: Termitidae), especie clave en el Desierto Chihuahuense</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1987</style></year></dates><volume><style face="normal" font="default" size="100%">73</style></volume><pages><style face="normal" font="default" size="100%">29-46</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">(In Spanish with English abstract)</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1987-91812</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Fisher, F. M.</style></author><author><style face="normal" font="default" size="100%">Parker, L. W.</style></author><author><style face="normal" font="default" size="100%">Anderson, J. P.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Nitrogen mineralization in a desert soil: Interacting effects of soil moisture and nitrogen fertilizer</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1987</style></year></dates><volume><style face="normal" font="default" size="100%">51</style></volume><pages><style face="normal" font="default" size="100%">1033-1041</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The responses of N mineralization to two patterns of supplemental water, N fertilizer, and a drying-wetting episode were examined on order to evaluate the effects of variation in timing and intensity of natural precipitaion on N avialability.  Field plots received either 6 mm water/week or 25 mm water/month with or without 10 g N m-2.  Samples were collected three times from July 1984 to March 1985 and incubated in the lab for 28 d.  The effects of drought were simulated by drying soil at 35 degrees C for 28 d followed by 168-d leaching incubations.  Supplemental water reduced 28-d mineralization by 22% in soil collected during dry and moderate soil moisture conditions (July 1984, October 1984) but had no effect on soils collected during a moist period (March 1985).  Nitrogen fertilizer had no effect on 28-d mineralization in soils from July but increased  28-d mineralization by 58% in soils from October and March.  Air-drying increased mineralization rates across all field treatments during the first 14 d of the 168-d leaching incubations.  Mineralization rates were lower in soils from watered plots in both the air-dry and field-moist treatments.  Air-drying interacted with both the water and N treatments by increasing watering effects and decreasing feritlizer N effects.  The observed drying effects appear to be a net result of several processes that, on the whole, tend to increase N availability. Mineralization rates in both experiments were lower in 6 mm/week soils than in 25 mm/month soils which, in turn, were lower than unwatered controls.  We hypothesize that increased moisture availability eventually leads to losses of minerlizable N as initially rapid mineralizaiton converts organic N to inorganic forms that are readily lost from the soil.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1987-91839</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Gutierrez, JR</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Responses of Chihuahuan Desert herbaceous annuals to rainfall augmentation</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1987</style></year></dates><volume><style face="normal" font="default" size="100%">12</style></volume><pages><style face="normal" font="default" size="100%">127-139</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Densities and biomass of annual herbaceous plants were compared on plots receiving supplemental water of 25 mm at 4-week intervals or 6.6mm per week, and plots receiving only natural rainfall.  During the first summer, there were no significant differences in total biomass between treatments, but the density and biomass of two species, &lt;i&gt;Astragalus tephrodes&lt;/i&gt; and &lt;i&gt;Euphorbia micormera&lt;/i&gt;, were greater on the watered plots.  Several spring annuals responded to supplemental water and by late spring (April) there were decreases in biomass on the watered plots, with the greatest decreases on the 6.3 mm per week plots.  Few species of summer annuals responded to supplemental water during the second year, possibly as a result of smaller rain events and/or limitation of available nitrogen.  Root shoot biomass ratios were between 0.15 and 0.25 for winter-spring annuals and 0.04 and 0.03 for summer annuals.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1987-91844</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">MacKay, William P.</style></author><author><style face="normal" font="default" size="100%">Silva, Solange</style></author><author><style face="normal" font="default" size="100%">Loring, Steven J.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">The role of subterranean termites in the decomposition of above ground creosotebush litter</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1987</style></year></dates><volume><style face="normal" font="default" size="100%">13</style></volume><pages><style face="normal" font="default" size="100%">235-239</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We investigated the role of the termite &lt;i&gt;Gnathamitermes tubiformans&lt;/i&gt; (Isoptera: Termitidae) in the breakdown of above ground creosotebush (&lt;i&gt;Larrea tridentata&lt;/i&gt;) litter in the northern Chihuahuan Desert of New Mexico, USA.  Comparison of decomposition rates of control plots with termite-excluded plots demonstrated that termites (and microarthropods) had no significant effect on mass loss.  This species normally consumes other organic matter and only uses creosotebush litter when nothing else is available.  This keystone species therefore plays a minor role in the breakdown of surface litter of the dominant shrub of the Chihuahuan Desert.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1987-91845</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Moorhead, Daryl L.</style></author><author><style face="normal" font="default" size="100%">Freckman, Diana W.</style></author><author><style face="normal" font="default" size="100%">Reynolds, James F.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">A simulation model of soil nematode population dynamics: effects of moisture and temperature</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1987</style></year></dates><volume><style face="normal" font="default" size="100%">30</style></volume><pages><style face="normal" font="default" size="100%">361-372</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We are currently constructing a simulation of primary productivity, decomposition and nitrogen cycling in a Chihuahuan desert ecosystem (Moorhead &lt;i&gt;et al.&lt;/i&gt; 1987).  This ecosystem simulation model will be used to address hypotheses concerning mechanisms of interactions and feedbacks which exist between the various organisms involved in carbon and nitrogen flow in deserts.  The soil organism community is an important component of this model because of its recognized role in regulating numerous processes, e.g., nitrogen mineralization (Swift &lt;i&gt;et al.&lt;/i&gt; 1979, Anderson &lt;i&gt;et al.&lt;/i&gt; 1985).  In this paper, we present a descriptive submodel of the population dynamics of a general bacterivorous nematode as influenced by soil temperature and moisture.  Recent investigations suggest that nematodes may play an important role in regulating decomposition processes and nutrient cycling by grazing on microflora and microfauna (Yeates 1979, Ingham &lt;i&gt;et al.&lt;/i&gt; 1985).</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1987-91847</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Lightfoot, David C.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Variation in insect densities on desert creosotebush: is nitrogen a factor?</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1987</style></year></dates><volume><style face="normal" font="default" size="100%">68</style></volume><pages><style face="normal" font="default" size="100%">547-557</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">A field experiment was conducted to assess the effects of nitrogen and water on the densities and taxonomic and trophic compositions of arthropods on the foliage of desert creosotebush (&lt;i&gt;Larrea tridentata&lt;/i&gt;).  Nitrogen and water were manipulated through a series of fertilizer and irrigation treatments applied to naturally growing creosotebush shrubs at a site in the northern Chihuahuan Desert.  Water with nitrogen, and nitrogen fertilization alone, significantly increased creosotebush foliage production and foliar nitrogen contents.  Foliage production, foliar nitrogen contents, and numbers of foliage arthropods were all higher in the late spring than in the mid or late summer.  Numbers of foliage arthropods increased significantly on fertilized plants in the late spring.  Water treatments alone had no effect on numbers of foliage arthropods, but a positive water-fertilizer interaction effect on numbers of foliage arthropods was evident in the late spring.  Overall, there were significant positive correlations between foliage production, foliar nitrogen contents, and foliage arthropod densities.  Photophagous sap-sucking insects accounted for the majority of arthropods on creosotebush, and their densities varied most in relation to foliage production and foliar nitrogen contents.  Results of our study demonstrated that sap-sucking phytophagous insects are more responsive than leaf-chewing insects to increased nitrogen content of creosotebush foliage, and that much of the between-plant variation in densities of phytophagous insects within a stand of creosotebush may be due to sap-sucking insects tracking variable foliar nitrogen.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1987-91853</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Moorhead, Daryl L.</style></author><author><style face="normal" font="default" size="100%">Reynolds, James F.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">A conceptual model of primary productivity, decomposition, and nitrogen cycling in the Chihuahuan creosotebush desert</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1986</style></year></dates><volume><style face="normal" font="default" size="100%">2</style></volume><pages><style face="normal" font="default" size="100%">215-222</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The conceptual framework for a simulation model of primary productivity, decomposition and nitrogen cycling in a shrub-dominated desert ecosystem in southern New Mexico is presented.  This model is based on our previous attempt to simulate carbon allocation patterns in the desert shrub &lt;i&gt;Larrea tridentata&lt;/i&gt; Cov., which demonstrated that moisture patterns alone are insufficient to predict desert productivity.  These results, as well as others, suggest that mineral nutrients, especially nitrogen, may also be an important determinant of productivity in arid environments.  Our current research in the Chihuahuan desert is directed towards elucidating the numerous biotic and abiotic interactions that determine the rates and directions of carbon, nitrogen and water fluxes in this ecosystem.  The development of this working model will serve as a tool to accomplish three major objectives: (1) to synthesize the large amounts of existing data on decomposition and nitrogen cycling in deserts, (2) to quantify our present state of knowledge about the structure and function of ecosystem components important in carbon and nitrogen dynamics in deserts, and (3) to address hypotheses concerning the complex mechanisms of interactions and feedbacks among the organisms involved in carbon and nitrogen exchanges in deserts.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1986-91875</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>6</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors><secondary-authors><author><style face="normal" font="default" size="100%">Whitford, W. G. (ed.)</style></author></secondary-authors></contributors><titles><title><style face="normal" font="default" size="100%">Decomposition and nutrient cycling in deserts</style></title><secondary-title><style face="normal" font="default" size="100%">Pattern and Process in Desert Ecosystems</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1986</style></year></dates><publisher><style face="normal" font="default" size="100%">University of New Mexico Press</style></publisher><pub-location><style face="normal" font="default" size="100%">Albuquerque, New Mexico</style></pub-location><pages><style face="normal" font="default" size="100%">93-117</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The results of the recent International Biological Program and other studies suggest that nutrients, especially nitrogen, may limit productivity in desert ecosystems when moisture is available.  Few studies examined decomposition processes in desert ecosystems prior to the initiation of our work, but here were fairly extensive efforts focused on nitrogen processes in desert ecosystems as part of the International Biological Program.  In this review, I will address the problem of both decomposition and nutrient cycling processes in desert ecosystems and attempt, wherever possible, to demonstrate the relationships between these processes and primary productivity.  Since these processes are mediated via the soil biota, I will emphasize soil biotic interactions and their importance, where these are known or suspected.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1986-91878</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">MacKay, William P.</style></author><author><style face="normal" font="default" size="100%">Silva, Solange</style></author><author><style face="normal" font="default" size="100%">Lightfoot, David C.</style></author><author><style face="normal" font="default" size="100%">Pagani, Maria Inez</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Effect of increased soil moisture and reduced soil temperature on a desert soil arthropod community</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1986</style></year></dates><volume><style face="normal" font="default" size="100%">116</style></volume><pages><style face="normal" font="default" size="100%">45-56</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The effects of soil moisture and temperature on arthropod communities were experimentally examined in the northern Chihuahuan Desert of New Mexico.  Shaded plots were established which lowered the soil temperature several degrees; some plots received artificial rainfall to increase soil moisture.  Shading reduced soil temperature at 5-cm depth 7-10 C.     Soil moisture at 5 cm accounted for most of the variation in surface activity of subterranean termites (r values between 0.3 and 0.7).  Termites did not respond to temperature differences.  When all soils were at field capacity, there was no difference in termite activity in shaded and unshaded plots.  There were higher densities of microarthropods in litter bags on the shaded plots than on the unshaded plots.  Numbers of microarthropods were an order of magnitude larger in litter bags on watered and shaded plots than on other plots.  Lower litter temperatures apparently affect litter arthropods more than increased soil moisture.  Shade had no effect on ant colonies but there were fewer colonies on the watered plots.     There was between 40 and 59% mass loss from creosotebush leaf litter after 7 months on all plots.  Water and soil temperature had no effect on decomposition rates.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1986-91883</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Elkins, Ned Z.</style></author><author><style face="normal" font="default" size="100%">Sabol, George V.</style></author><author><style face="normal" font="default" size="100%">Ward, Timothy J.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">The influence of subterranean termites on the hydrological characteristics of a Chihuahuan Desert ecosystem</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1986</style></year></dates><volume><style face="normal" font="default" size="100%">68</style></volume><pages><style face="normal" font="default" size="100%">521-528</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Rainfall simulation at an average intensity of 124 mm.h-1 was used to compare infiltration and runoff on arid areas where subterranean termites had been eliminated four years prior to the initiation of the study (termite free) with adjacent areas populated by subterranean termites (termite present).  Infiltration rates on termite free plots with less than 5% perennial plant cover were significantly lower 51.3+-6.8 mm.h-1 than rates on comparable termites present plots 88.4+-5.6 mm.h-1.  On plots centered on Larrea tridentata shrubs, there were no differences in infiltration rates with or without termites.  Plots with shrub cover had the highest infiltration rates 101+-6 mm.h-1.  Highest runoff volumes were recorded from termite free &lt;5% grass cover plots and the lowest from plots with shrubs.  There were no differences in suspended sediment concentrations from termites present and termite free plots.  Average bed load concentration was more than three times greater for termite free, &lt;5% cover plots than from termite present, &lt;5% cover plots. The reduction in infiltration, high runoff volumes and high bedloads from termite free areas without shrub cover is relatd to increased soil bulk density resulting from the collapse of subterranean galleries of the termites that provide avenues of bulk flow into the soil.  Subterranean termites affect the hydrology of Chihuahuan desert systems by enhancing water infiltration and retention of top soil.  The presence of a shrub canopy and litter layer cancels any effect of subterranean termites on hydrological parameters.  Since approximately 2/3 of the area is not under shrub canopies, subterranean termites are considered to be essential for the maintenance of the soil water characteristics that support the present vegetation.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1986-91889</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Zak,  John C.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">The occurrence of hypogeous ascomycete in the northern Chihuahuan Desert</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1986</style></year></dates><volume><style face="normal" font="default" size="100%">78</style></volume><pages><style face="normal" font="default" size="100%">840-841</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Sporocarps of the hypogeous ascomycete &lt;i&gt;Carbonmyces emergens&lt;/i&gt; Gilky were collected in the northern Chihuahuan Desert, at the entrance to the Jornada Experimental Range, 25 km NNE of Las Cruces, New Mexico on March 13, 1985.....</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1986-91892</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Steinberger, Y.</style></author><author><style face="normal" font="default" size="100%">MacKay, W.</style></author><author><style face="normal" font="default" size="100%">Parker, L. W.</style></author><author><style face="normal" font="default" size="100%">Freckman, D</style></author><author><style face="normal" font="default" size="100%">Wallwork, J. A.</style></author><author><style face="normal" font="default" size="100%">Weems, D.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Rainfall and decomposition in the Chihuahuan desert</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1986</style></year></dates><volume><style face="normal" font="default" size="100%">68</style></volume><pages><style face="normal" font="default" size="100%">512-515</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We tested the hypothesis that rates of decomposition in a desert should be higher following single large rain events of 25 mm than evenly spaced 6 mm events and that supplemental rainfall should result in higher populations of soil biota.  There were no significant differences in mass losses of creosotebush, &lt;i&gt;Larrea tridentata&lt;/i&gt;, leaf litter on plots receiving water supplementation and no added water.  On some sampling dates, there were higher mass losses in the 6 mm/week-1 treatment.  Weekly rainfall produced higher coefficients of variation in mass losses than the other rainfall regimes.  A single event pulse compared with weekly pulses of rainfall during the normal &quot;dry&quot; period resulted in no differences in mass losses.  Microarthropods and nematodes exhibited numerical responses to supplemental rainfall but the litter microflora did not.  These studies provide direct experimental evidence that the conventional wisdom linking decomposition to rainfall in deserts is wrong.  The studies also suggest that the effects of litter fauna on surface litter decomposition are minimal; therefore, future studies should focus on activities of the microflora.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1986-91901</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Wallwork, J. A.</style></author><author><style face="normal" font="default" size="100%">MacQuitty, Miranda</style></author><author><style face="normal" font="default" size="100%">Silva, Solange</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Seasonality of some Chihuahuan Desert soil oribatid mites (Acari: Cryptostigmata)</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1986</style></year></dates><volume><style face="normal" font="default" size="100%">208</style></volume><pages><style face="normal" font="default" size="100%">403-416</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">1. Reproductive strategies of four species of oribatid mites were investigated in the Chihuahuan Desert from 1981 to 1984.     2. Breeding activity coincided with the summer rainfall period in three of the four cases: &lt;i&gt;Passalozetes neomexicanus, P. californicus&lt;/i&gt; and &lt;i&gt;Jornadia larreae&lt;/i&gt;.  This pattern was not changed by the application of simulated rainfall at other times of the year.  The strict seasonality of reproductive behavior is interpreted as an outcome of strong selection pressure to recruit only when food quality and quantity and microclimate are most favorable.     3. &lt;i&gt;Joshuella striata&lt;/i&gt; showed a more flexible pattern which was essentially bimodal.  Periods of egg production occurred in winter and also during the summer rainfall period.  This pattern is consistent with the known distribution of this species in winter- and summer-rainfall deserts in south-western USA.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1986-91904</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Schaefer, Douglas</style></author><author><style face="normal" font="default" size="100%">Wisdom, Wendy</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Soil movement by desert ants</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1986</style></year></dates><volume><style face="normal" font="default" size="100%">31</style></volume><pages><style face="normal" font="default" size="100%">273-274</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Estimates of quantities of soil moved by the activities of ants from the soil profiel to the surface in a shinnery oak (&lt;i&gt;Quercus harvardii&lt;/i&gt;) - mesquite (&lt;i&gt;Prosopis glandulosa&lt;/i&gt;) area 40 km east of Carlsbad, NM.  Soils were sandy loams. The average quantity of soil moved to the surface by ants during the period of surface activity (May - September) was 84.2 +/- 4 g m&lt;sup&gt;-2&lt;/sup&gt;.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1986-91910</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">MacKay, William P.</style></author><author><style face="normal" font="default" size="100%">Blizzard, James H.</style></author><author><style face="normal" font="default" size="100%">Miller, Jacqueline J.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Analysis of above-ground gallery construction by the subterranean termite &lt;i&gt;Gnathamitermes tubiformans&lt;/i&gt; (Isoptera: Termitidae)</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1985</style></year></dates><volume><style face="normal" font="default" size="100%">14</style></volume><pages><style face="normal" font="default" size="100%">470-474</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">&lt;i&gt;Gnathamitermes tubiformans&lt;/i&gt; (Buckley), a common termite species in the northern Chihuahuan Desert of North America, builds mud galleries around standing dead vegetation and other food materials after periods of rain.  The termites graze only the surface of standing dead branches, tissues highest in nitrogen content.  We hypothesized that termites invest more energy in gallery construction than they obtain from the wood they consume.  We estimated energy costs of gallery construction from analysis of gallery material and construction behavior of the termites.  In addition to obtaining a food source relatively high in nitrogen, the estimated energy invested in gallery construction.  Therefore, the termites obtain much more energy from wood than they invest in gallery construction.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1985-91923</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Wallwork, J. A.</style></author><author><style face="normal" font="default" size="100%">Kamill, B. W.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Distribution and diversity patterns of soil mites and other microarthropods in a Chihuahuan Desert site</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1985</style></year></dates><volume><style face="normal" font="default" size="100%">9</style></volume><pages><style face="normal" font="default" size="100%">215-231</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">This paper reports the results of a pilot survey of the patterns of distribution and species diversity of soil microarthropods from 12 different sites in a Chihuahuan Desert watershed in southern New Mexico....  An Index of Diversity, calculated for the various groups of microarthropods at the 12 sties, was very variable, but values approximating to those reported for the microarthropod fauna of an English beech woodland were obtained for several sites.  The equitability component of this species diversity provided a good indicator of the relative stability of the sites studied.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1985-91927</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Parker, L. W.</style></author><author><style face="normal" font="default" size="100%">Ryder-White, J.</style></author><author><style face="normal" font="default" size="100%">Thomas, S.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Effects of oxamyl and chlordane on the activities of nontarget soil organisms</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1985</style></year></dates><volume><style face="normal" font="default" size="100%">1</style></volume><pages><style face="normal" font="default" size="100%">141-148</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The effect of two pesticides, oxamyl and chlordane, on nontarget soil biota were examined in microcosms.  Neither oxamyl nor chlordane had an effect on rates of litter decomposition or soil and litter respiration.  There were differences in numbers of nematodes and protozoans and in biomass of bacteria and fungi in microcosms with and without chlordane on some sampling dates.  One of the nematodes, &lt;i&gt;Pelodera&lt;/i&gt; sp., died out in all of the microcosms within 30 days.  Although the pesticide chlordane had no measurable effect on the activities of the soil biota as measured by respiration and mass loss, it did affect the population sizes and biomass of some grazers of soil biota.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1985-91928</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Schaefer, Douglas</style></author><author><style face="normal" font="default" size="100%">Steinberger, Yosef</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">The failure of nitrogen and lignin control of decomposition in a North American desert</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1985</style></year></dates><volume><style face="normal" font="default" size="100%">65</style></volume><pages><style face="normal" font="default" size="100%">382-386</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We measured mass losses of both buried and surface litter of six litter types: leaves of the perennial evergreen shrub, &lt;i&gt;Larrea tridentata&lt;/i&gt;, leaves of the winter deciduous perennials &lt;i&gt;Flourensia cernua, Prosopis glandulosa&lt;/i&gt; and &lt;i&gt;Chilopsis linearis&lt;/i&gt; ( a desert riparian species), and evergreen monocot, &lt;i&gt;Yucca elata&lt;/i&gt;, and a mixture of annual plants.  These species differed in lignin content and carbon-nitrogen ratios.  There was no correlation between rates of mass loss and percent lignin, carbon-nitrogen ration, or lignin-nitrogen ratio.  The leaves of &lt;i&gt;F. cernua&lt;/i&gt; and the mixed annuals exhibited the highest rates of mass loss.  Surface litter of &lt;i&gt;Y. elata&lt;/i&gt;, and the mixed annuals and &lt;i&gt;C. linearis&lt;/i&gt; exhibited higher mass loss than buried litter of the same species.  The patterns of mass loss occurring as a negative exponential and surface litter exhibiting low rates in winter and spring and high rates in summer.  There was no correlation between mass loss in surface bags that were field exposed for 1 month and actual evapotranspiration (AET) but there was a correlation between AET and mass losses in buried litter.  A model relating mass loss to AET and initial lignin content underestimated mass losses in all species examined.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1985-91930</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Fowler, Harold G.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Host plant ovipositional preferences and usage by &lt;i&gt;Oecleus nolinus&lt;/i&gt; (Homoptera: Cixiidae)</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1985</style></year></dates><volume><style face="normal" font="default" size="100%">30</style></volume><pages><style face="normal" font="default" size="100%">610-611</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">During May and June , 1979, we observed large numbers of O&lt;i&gt;. nolinus&lt;/i&gt; at the Jornada Experimental Range, 60 km NNE of Las Cruces, Dona Ana Co., New Mexico.  They used three plant species (&lt;i&gt;Yucca baccata, Y. elata &lt;/i&gt;and&lt;i&gt; Dasyliron wheeleri&lt;/i&gt;) as ovipostional sites.  &lt;i&gt;Dasyliron wheeleri&lt;/i&gt; is an apparent new host for &lt;i&gt;O. nolinus&lt;/i&gt;.  Townsend (Psyche 6:353-354, 1928) recorded an &lt;i&gt;Oecleus&lt;/i&gt;, probably &lt;i&gt;O. nolinus&lt;/i&gt; but recorded as &lt;i&gt;O. decens&lt;/i&gt;, ovipositing on &lt;i&gt;Yucca angustifolia&lt;/i&gt; (=&lt;i&gt;Y. elata?&lt;/i&gt;) and &lt;i&gt;Y. macrocarpa&lt;/i&gt; (=&lt;i&gt;Y. baccata?&lt;/i&gt;) in southern New Mexico.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1985-91933</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Steinberger, Yosef</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Microarthropods of a desert tabosa grass (&lt;i&gt;Hilaria mutica&lt;/i&gt;) swale</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1985</style></year></dates><volume><style face="normal" font="default" size="100%">114</style></volume><pages><style face="normal" font="default" size="100%">225-234</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We examined soil microarthropod populations inhabiting a clay-silt soil of a tabosa grass (&lt;i&gt;Hilaria mutica&lt;/i&gt;) swale in southern New Mexico....  Overall densities of microarthropod groups were correlated with soil moisture but many individual taxa were not.  The most numerous and frequently occurring taxa [nanorchestid, tydeid and bdellid mites (Progtigmata); &lt;i&gt;Aphelacarus&lt;/i&gt; sp. and &lt;i&gt;Cosmochthonius&lt;/i&gt; sp. (Cryptostigmata)] are common in all Chihuahuan desert habitats examined to date and are common in other North American desert areas.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1985-91940</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Silva, Solange I.</style></author><author><style face="normal" font="default" size="100%">MacKay, William P.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">The relative contributions of termites and microarthropods to fluff grass litter disappearance in the Chihuahuan Desert</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1985</style></year></dates><volume><style face="normal" font="default" size="100%">67</style></volume><pages><style face="normal" font="default" size="100%">31-34</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We tested the hypotheses that both subterranean termites and soil microarthropods are important in the disappearance of fluff grass (&lt;i&gt;Erioneuron pulchellum&lt;/i&gt;) litter on the soil surface by an experiment designed to separate termite and microarthropod effects.  Subterranean termites (&lt;i&gt;Gnathamitermes tubiformans&lt;/i&gt;) removed more than 50% of the fluff grass litter in one year.     Since there was no difference in mass loss of fluff grass with microarthropods present or excluded, they had no effect on decomposition of fluff grass litter.  Microarthropod densities increased during the first 3 months then slowly decreased.  The densities of microarthropods in fluff grass litter were too low to have a measurable effect of decomposition even if we assumed that the microarthropods consumed litter equivalent to their body weight each day.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1985-91945</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Kamill, Bernardette W.</style></author><author><style face="normal" font="default" size="100%">Steinberger, Y.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Soil microarthropods from the Chihuahuan Desert of New Mexico</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1985</style></year></dates><volume><style face="normal" font="default" size="100%">205</style></volume><pages><style face="normal" font="default" size="100%">273-286</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">An account is given of the soil- and litter-dwelling microarthropods collected under three species of desert shrub in southern New Mexico.  Particular attention is paid to the acarine component which represents 80% of the microarthropod fauna.  Comparisons made with samples collected one hour after wetting show that only the Collembola respond rapidly to changes in the moisture content of the soil.  The results of the study suggest that the depth and stability of the surface litter determine the degree to which microarthropod activity is affected by the application of water.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1985-91946</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Fowler, Harold G.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Structure and organization of a winter community of cavity-inhabiting, web-building spiders (Pholocidae and Theridiidae) in a Chihuahuan Desert habitat</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1985</style></year></dates><volume><style face="normal" font="default" size="100%">8</style></volume><pages><style face="normal" font="default" size="100%">57-65</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Populations of Chihuahuan Desert spiders that construct webs in naturally occurring cavities were followed over a 20-week-period with modified pitfall traps.  Of the three species studied, &lt;i&gt;Psilochorus imitatus &lt;/i&gt;(Pholocidae) was the most abundant, followed in order by &lt;i&gt;Artema atlanta &lt;/i&gt;(Pholocidae) and &lt;i&gt;Latroductus hesperus&lt;/i&gt; (Theridiidae).  Canonical correlation analysis indicated a strong dependence of &lt;i&gt;L. hesperus&lt;/i&gt; upon soil temperatures.  A principal axis factor analysis explained 87 per cent of the variance in the spider-weather-habitat aspect system with five common factors.  This model also gave a good fit to all monitored variables.  This analysis demonstrated the importance of habitat aspect upon spider distributions, and allowed an examination of the partitioning of niche space by the three species.  Experimental laboratory manipulations suggested that groups of &lt;i&gt;A. atlanta&lt;/i&gt; can behaviorally dominate solitary &lt;i&gt;L. hesperus&lt;/i&gt; females by restricting orb web construction, and suggested that patterns observed in the field may be shaped by interspecific competition.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1985-91947</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Parker, L. W.</style></author><author><style face="normal" font="default" size="100%">Santos, P. F.</style></author><author><style face="normal" font="default" size="100%">Phillips, J.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Carbon and nitrogen dynamics during the decomposition of litter and roots of a Chihuahuan Desert annual &lt;i&gt;Lepidium lasiocarpum&lt;/i&gt;</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1984</style></year></dates><volume><style face="normal" font="default" size="100%">54</style></volume><pages><style face="normal" font="default" size="100%">339-360</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Carbon and nitrogen dynamics were analyzed during the decomposition of litter and roots of the desert ephemeral pepperweed (&lt;i&gt;Lepidium lasciocarpum&lt;/i&gt;).  We treated litter bags with the insecticide chlordane and the fungicides benomyl and captan to eliminate or restrict groups of soil biota.     Data from this study re-emphasize the importance of microarthropods as regulators or decomposition in deserts and suggest that predation by nematodes or protozoa on bacteria and fungi contributes to rate regulation.  Nitrogen flux data suggest that when spring ephemeral plant production is high, decomposition of ephemeral roots with attendant nitrogen immobilization can reduce the nitrogen available to creosotebush, &lt;i&gt;Larrea tridentata&lt;/i&gt;, thus reducing shrub production.  Higher taxa of soil biota, i.e., nematodes and miroarthropods, may thus be important regulators of nitrogen fluxes and of mass loss in decomposition.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1984-91955</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Santos, Perseu F.</style></author><author><style face="normal" font="default" size="100%">Elkins, Ned Z.</style></author><author><style face="normal" font="default" size="100%">Steinberger, Yosef</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">A comparison of surface and buried &lt;i&gt;Larrea tridentata&lt;/i&gt; leaf litter decomposition in North American hot deserts</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1984</style></year></dates><volume><style face="normal" font="default" size="100%">65</style></volume><pages><style face="normal" font="default" size="100%">278-284</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We conducted studies of mass losses from surface and buried litter bags in four North American hot desert areas to test the following hypotheses: (1) leaf litter disappearance in hot deserts is independent of actual evapotranspiration, (2) buried litter disappearance is a function of actual evapotranspiration, (3) the patter of microarthropod colonization of buried leaf litter is a function of the stage of decomposition, and (4) elimination of microarthropod results in reduced rates of decomposition and increased numbers of free-living nematodes.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1984-91956</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Fowler, Harold G.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Coordinated prey capture by Novomessor cockerelli (Hymenoptera: Formicidae)</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1984</style></year></dates><volume><style face="normal" font="default" size="100%">91</style></volume><pages><style face="normal" font="default" size="100%">328-332</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">&lt;i&gt;Novomessor cockerelli&lt;/i&gt; uses coordinated behavior to subdue large orthopteran prey.  When a partially disabled grasshopper is encountered, the first worker finding it mounts the dorsum of the grasshopper and clamps its mandibles over the wings, thus preventing escape by flight.  Workers which arrive subsequently systematically remove or subjugate additional appendages.  Behavioral coordination allows &lt;i&gt;N. cockerelli&lt;/i&gt; to efficiently exploit large orthopterna prey which would otherwise escape if workers attempted to capture these individually.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1984-91958</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Steinberger, Y.</style></author><author><style face="normal" font="default" size="100%">Freckman, DW</style></author><author><style face="normal" font="default" size="100%">Parker, L. W.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Effects of simulated rainfall and litter quantities on desert soil biota: nematodes and microarthropods</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1984</style></year></dates><volume><style face="normal" font="default" size="100%">26</style></volume><pages><style face="normal" font="default" size="100%">267-274</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The experiments reported here were designed to test the hypothesis that numerical responses of soil fauna to simulated rainfall would occur only in soils having an adequate leaf litter cover.     The soil microarthropods responded to artificial rainfall as hypothesized, that is, the most abundant taxa responded to litter quantity and moisture but not to moisture in the absence of sufficient substrate.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1984-91964</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Parker, L. W.</style></author><author><style face="normal" font="default" size="100%">Freckman, DW</style></author><author><style face="normal" font="default" size="100%">Steinberger, Y.</style></author><author><style face="normal" font="default" size="100%">Driggers, L.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Effects of simulated rainfall and litter quantities on desert soil biota: soil respiration, microflora and protozoa</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1984</style></year></dates><volume><style face="normal" font="default" size="100%">27</style></volume><pages><style face="normal" font="default" size="100%">185-195</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We experimentally tested the hypothesis that simulated rainfall would trigger higher levels of activity in soil biota under large surface accumulation of litter in a Chihuahuan desert soil.   Bacterial biomass was highest on days 6 and 12 in plots receiving simulated rain and increased with increasing litter.  The turnover of themicrobial biomass was estimated as 6.97 days and was independent of either water or litter quantity.  Soil respiration was higher in the wet treatments on days 0 and 6.  When treatments were averaged across time, the highest soil respiration was in the 150 g m-2 litter, watered plots.  The same pattern was observed in the dry treatments after natural rain events.   On day 6, protozoa were higher in the wet plots; protozoa in the dry plots were 100% cystic while those in the wet plots were 100% trophic.  Protozoan numbers were independent of litter quantity and reached the maximum on day 18.  Amoebae were the dominant protozoa with an average population size of 25,000 g-1.  Flagellates were intermediate in numbers (4,900 g-1) while ciliates were the least abundant (700 g-1).</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1984-91965</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Wallwork, John A.</style></author><author><style face="normal" font="default" size="100%">Kamill, B. W.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Life styles of desert litter-dwelling microarthropods: a reappraisal based on the reproductive behavior of Cryptostigmatid mites</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1984</style></year></dates><volume><style face="normal" font="default" size="100%">80</style></volume><pages><style face="normal" font="default" size="100%">163-169</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Studies in a series of Chihuahuan Desert litter and soil habitats confirmed that reproductive activity was most pronounced following the major rainfall, as in the Mojave Desert.  Immediately after the summer rains, evidence was found of considerable breeding activity in more than 60% of the oribatid species studied in the former desert.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1984-91967</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Steinberger, Yosef</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Spatial and temporal relationships of soil microarthropods on a desert watershed</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1984</style></year></dates><volume><style face="normal" font="default" size="100%">26</style></volume><pages><style face="normal" font="default" size="100%">275-284</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">...we hypothesized that microarthropod densities and numbers of taxa would be highest at the base of a closed basin watershed where organic matter and water accumulate (run-on area) and lowest at the top of the watershed (run-off area), providing the soils sampled were under the same plant species....  we hypothesized that as the soils dried following a rain event, the number of taxa and population densities of microarthropods would remain high for longer periods at the base of the watershed than at the top.     The data collected in the study force us to reject our original hypotheses, i.e., that microarthropod population densities and number of taxa should be higher at the base of the watershed, exhibit a greater increase in size in response to precipitation and remain active for a longer time than on the upper slopes of the watershed.  The relationships found in this study were almost the reverse of those hypothesized.  Although soil organic matter and percent soil moisture were consistently higher at the base of the watershed, soil microarthropod populations were either lower than or equal to those found on the upper slopes.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1984-91979</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Steinberger, Y.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">The contribution of rodents to decomposition processes in a desert ecosystem</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1983</style></year></dates><volume><style face="normal" font="default" size="100%">6</style></volume><pages><style face="normal" font="default" size="100%">177-181</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Excavations made by desert rodents during the late non-growing season (April-August) accumulated litter amounts varying between 5.2 and 17.6 kg/ha and over a 1-year period 55.9 kg/ha of litter was buried in such excavations.  There was a higher nitrogen content in litter in October, 17.6 +- 0.5 ug/g than the rest of the year, 1.5 +- 1.4 ug/g.  Litter bag studies of decomposition of small quantities of buried litter similar to that accumulated in rodent excavations exhibited higher rates of decomposition than larger quantities of buried litter reported in the literature.  Rodent excavating activity increases rates of decomposition and organic matter turnover and may effect the distribution of ephemeral plants in warm desert ecosystems.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1983-92001</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Steinberger, Y.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">The contribution of shrub pruning by jackrabbits to litter input in a Chihuahuan Desert ecosystem</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1983</style></year></dates><volume><style face="normal" font="default" size="100%">6</style></volume><pages><style face="normal" font="default" size="100%">183-187</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Jackrabbits, &lt;i&gt;Lepus californicus&lt;/i&gt;, prune stems from creostoesbushes &lt;i&gt;Larrea tridentata&lt;/i&gt; during the dry winter months, eating the previous season new woody stems allowing the leaves and old wood to fall the the ground.  This unconsumed material was 66 kg/ha/year of stem and 35 kg/ha/year of leaves; approximately one-fifth of the quantity of shrub litter input by natural infall.  Jackrabbits preferentially pruned stems of shrubs with higher tissue moisture content.  Rabbits tend to prune stems from the same shrubs in successive years.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1983-92002</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Urbaniak, Sandra</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Decomposition rates of various quantities of buried litter in a desert</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1983</style></year></dates><volume><style face="normal" font="default" size="100%">28</style></volume><pages><style face="normal" font="default" size="100%">111-112</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">In the Chihuahuan desert, litter is buried by wind and water around obstructions and in excavations made by animals (Santos and Whitford, Ecology 62:654-663, 1981; Steinberger and Whitford, unpublished data).  Based on the data of Whitford, &lt;i&gt;et. al&lt;/i&gt; (1980), we hypothesized that litter loss through decomposition would be highest in the large quantity litter bags.      Organic matter loss was greatest in the 1 gm, and least in the 50 gm bags.  There was no significant difference in organic matter loss among the 1 gm, 5 gm, and 10 gm quantities (p&gt;.05).  But, there was significant difference in organic matter loss between these and the 20 gm and 50 gm quantities (F= 63.6 p&lt;.0001) (Fig. 1).  Thus the relationship between litter quantity and decomposition was higher at higher litter accumulations....     The results of this experiment have important implications for litter decomposition in Chihuahuan desert ecosystems.  Litter accumulations in small excavations made by rodents in quantities less than 5 gm.  These accumulations are buried and as shown here, decomposition is rapid.  Litter also is buried in larger excavations, but these occur at a lower frequency and density than the small excavations.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1983-92003</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Fowler, Harold G.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Pre-dispersal seed feeding insects of a desert legume, &lt;i&gt;Astragalus nutallianus&lt;/i&gt;</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1983</style></year></dates><volume><style face="normal" font="default" size="100%">28</style></volume><pages><style face="normal" font="default" size="100%">466-469</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">During the spring of 1979, we conducted surveys of the pre-dispersal seed-eating insect guild of loco weeds, &lt;i&gt;Astraglus nutallianus&lt;/i&gt; D.C.  Two alluvial plains (bajadas) separated by approximately 25 km, were surveyed.  The bajadas are on the Mt. Summerford watersheds on the New Mexico State University Experimental Range, 40 km NNE of Las Cruces, N.M.     On each site we classified the loco weeds into 5 relative density classes based on distance to nearest neighbor of the same species.  Distance classes in meters were 0-0.5, 0.5-1.0, 1.0-5.0, 5.0-10.0 and 10.0-20.0.  At least 10 plants in each of the density class areas were up rooted, place in plastic bags and transported to the laboratory.  We recorded the number of plants of other species within a 1.5 m radius of each plant collected.  All pods were stripped from each plant, and the total number of pods and the number of pods damaged by seed-eating insects were counted.  A subsample of insect damaged and undamaged pods were opened and the number of seeds present in each was recorded.  Another subsample was placed in containers to rear the larvae present.  The plant, devoid of pods, was oven dried and weighed.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1983-92028</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Parker, L. W.</style></author><author><style face="normal" font="default" size="100%">Miller, J.</style></author><author><style face="normal" font="default" size="100%">Steinberger, Y.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Soil respiration in a Chihuahuan Desert rangeland</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1983</style></year></dates><volume><style face="normal" font="default" size="100%">15</style></volume><pages><style face="normal" font="default" size="100%">303-309</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Soil respiration of a desert soil was measured at the New Mexico State University Ranch in Southern New Mexico.  Respiration rates were highest during late July and August after summer rains.  Soil respiration data were used to estimate soil organic matter turnover which was 54 yr using summer data and 20 yr using both summer and winter data.  The long turnover estimate for summer measurements resulted from temperatures above optimum in June and July.  Diurnal soil respiration was also measured after a simulated 2.54 cm rain event.  For both wetted and dry soils, temperature controlled the patterns of soil respiration with an optimum of near 41 C.  Activation energy values decreased form 84.91 to 39.5 kJ mol-1 when the soil was wetted.  A light-dark container method was tested as a possible means of estimated algal uptake of CO2, however, the method was not feasible for desert soils.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1983-92033</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Steinberger, Y.</style></author><author><style face="normal" font="default" size="100%">Ettershank, George</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Contributions of subterranean termites to the 'economy' of Chihuahuan desert ecosystems</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1982</style></year></dates><volume><style face="normal" font="default" size="100%">55</style></volume><pages><style face="normal" font="default" size="100%">298-302</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We examined the role of subterranean termites in decomposition of cattle dung, various herbaceous plant species and wood in a Chihuahuan desert ecosystem.  From July-September, termites removed dung at a rate of 0.63 g/day-1 accounting for a percent mass loss of 19.5-100%.  During the autumn subterranean termites consumed more than 50% of the leaves of the shrub &lt;i&gt;Larrea tridentata&lt;/i&gt;, the grass &lt;i&gt;Erioneuron pulchellum&lt;/i&gt; and annual plant &lt;i&gt;Lepidium lasiocarpum&lt;/i&gt; and &lt;i&gt;Baileya multiradiata&lt;/i&gt; but used very little of two other annuals &lt;i&gt;Eriastrum diffusum&lt;/i&gt; and &lt;i&gt;Eriogonum trichopes.  Yucca&lt;/i&gt; inflorescence stalks on plots with termites lost 23% of their original mass in 30 months while those on termite free soils lost 11%.  Elimination of termites resulted in reduction of fluff grass, &lt;i&gt;Erioneuron pulchellum&lt;/i&gt; biomass, thereby affecting the structure of the ecosystem.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1982-92051</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Repass, Robert</style></author><author><style face="normal" font="default" size="100%">Parker, Lawrence W.</style></author><author><style face="normal" font="default" size="100%">Elkins, Ned Z.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Effects of initial litter accumulation and climate on litter disappearance in a desert ecosystem</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1982</style></year></dates><volume><style face="normal" font="default" size="100%">108</style></volume><pages><style face="normal" font="default" size="100%">105-110</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We examined monthly litter disappearance from initial concentrations of 50g, 100g, 150g and 200g m-2.  Approximately 35%-50% of the litter disappeared each month from May-September.  In March and April litterfall input exceeded litter loss.  Litter loss was consistently higher in the 100g m-2 accumulation than from the other concentrations.  Stepwise regression analysis showed that litter loss varied as a  function of soil temperature at 15 cm (r2= 0.40) and that initial litter quantity was the second most important variable (increased r2 to 0.45).  Monthly litter disappearance was apparently independent of monthly rainfall.  Abiotic variables gave an r2 of 0.48, suggesting that much of the seasonal variation in litter disappearance is attributable to the soil biota.  Suppression of microarthropods by treating the soil with chlordane insecticide resulted in marked reduction in litter disappearance.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1982-92056</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Parker, L. W.</style></author><author><style face="normal" font="default" size="100%">Fowler, H. G.</style></author><author><style face="normal" font="default" size="100%">Ettershank, G.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">The effects of subterranean termite removal on desert soil nitrogen and ephemeral flora</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1982</style></year></dates><volume><style face="normal" font="default" size="100%">5</style></volume><pages><style face="normal" font="default" size="100%">53-59</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Total soil nitrogen and ephemeral plant density and biomass on plots treated with chlordane to eliminate termites were compared with untreated control plots at the Jornada validation site in the Chihuahuan desert.  Total soil nitrogen in the 0-2.5 and 10-20 cm depths was significantly higher for treated compared to control plots.  Other than increase soil N at the above two depths, the elimination of termites did not alter the spatial distribution of nitrogen around &lt;i&gt;Larrea tridentata&lt;/i&gt;.  Soil N in both treated and controlled plots was higher under the shrub canopy than in open areas, on the east side of shrubs than on the west, and in the surface soils than at lower depths.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1982-92057</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Elkins, Ned Z.</style></author><author><style face="normal" font="default" size="100%">Steinberger, Yosef</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Factors affecting the applicability of the AET model for decomposition in arid environments</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1982</style></year></dates><volume><style face="normal" font="default" size="100%">63</style></volume><pages><style face="normal" font="default" size="100%">579-580</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">There is considerable interest in the applicability of the model developed by Meentemeyer (1978), which predicts decomposition as a function of actual evapotranspiration (AET) and lignin, to environments other than forests.  Whitford et al. (1981&lt;i&gt;b&lt;/i&gt;) discussed exceptions to the Meentemeyer AET model in deserts and clearcut forests and concluded that in these environments, biological activity of soil microarthropod and termites, accounts for the deviations (higher rates) from the model.  We recently completed a study of decomposition in a semiarid desert-grassland transitional area that provides another independent test of the AET model.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1982-92059</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Fowler, Harold G.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Floral visitation by Chihuahuan Desert ants</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1982</style></year></dates><volume><style face="normal" font="default" size="100%">16</style></volume><pages><style face="normal" font="default" size="100%">879-881</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Experimental and observational tests with tropical lowland plant species and ants have generally rejected Janzen's (1977) hypothesis of deterrent chemicals in floral nectars....  Here we address the following two questions for desert plants: (1) do ants naturally visit desert flowers for floral nectar:, and (2) are floral nectars of desert plants repellent to ants?</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1982-92060</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Elkins, N. Z.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">The role of decomposition in a semi-arid ecosystem</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1982</style></year></dates><volume><style face="normal" font="default" size="100%">55</style></volume><pages><style face="normal" font="default" size="100%">303-310</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><accession-num><style face="normal" font="default" size="100%">LTER.1982-92067</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Elkins, Ned Z.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">The role of microarthropods and nematodes in decomposition in a semi-arid ecosystem</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1982</style></year></dates><volume><style face="normal" font="default" size="100%">55</style></volume><pages><style face="normal" font="default" size="100%">303-310</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We sampled the soil microarthropod community monthly in the oak-mesquite sand hill ecosystem.  Small fungiphagous prostigmated mites (pyemotids, lordalychids and tarsonemids) that dominated the soil fauna in winter were replaced by large predaceous mites (rhodacarids and laelapids) in summer and autumn.  We compared organic matter loss and microarthropod and nematode populaiton in shinnery oak (&lt;i&gt;Quercus harvardii&lt;/i&gt;) using insecticide and untreated litter in fiberglass litterbags.  Microarthropods extracted form litterbags showed a seasonal pattern similar to the soil cores except that collembolans and psocopterans were abundant in the litter and not in the soil cores.  Numbers of free living nematodes were consistently greater than from untreated litter.  The ratio of non-stylet bearing nematodes extracted from the litter decreased from 4:1 in one month bags to 0.8:1.0 in the one year bags.  Laboratory experiments showed that rhodacarid mites fed voraciously on nematodes.  Untreated litter ixhibited higher rates of organic matter loss than the insecticide treated litter; 20% and 35% respectively.  We suggest that the abundant mesostigmatid mites prey on free living nematodes and that eliminating the predators allows the nematodes to overgraze the fungi and bacteria.  The soil modifies the microclimate in buried litter allowing for higher biological activity, hence higher rates of decomposition.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1982-92068</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>6</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Freckman, DW</style></author><author><style face="normal" font="default" size="100%">Santos, P. F.</style></author><author><style face="normal" font="default" size="100%">Elkins, N. Z.</style></author><author><style face="normal" font="default" size="100%">Parker, L. W.</style></author></authors><secondary-authors><author><style face="normal" font="default" size="100%">Freckman, D. W. (ed.)</style></author></secondary-authors></contributors><titles><title><style face="normal" font="default" size="100%">The role of nematodes in decomposition in desert ecosystems</style></title><secondary-title><style face="normal" font="default" size="100%">Nematodes in Ecosystems</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1982</style></year></dates><publisher><style face="normal" font="default" size="100%">University of Texas Press</style></publisher><pub-location><style face="normal" font="default" size="100%">Austin</style></pub-location><pages><style face="normal" font="default" size="100%">98-117</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Although nematodes are numerous in the soils of most ecosystems, their contribution to soil respiration is relatively small (Sohlenius 1980).  Thus, judged on the basis of energy flow through an ecosystem, nematodes would have to be considered a minor component of such systems.  However, the contribution of a groups of organisms  to the functioning of a system cannot be judged solely on the basis of the quantity of energy processed by that group.  Chew (1974) suggested that while consumers may be relatively unimportant in energy flow, they may play important roles as rate regulators.  In this paper we review our findings to date on the role of nematodes in desert soil ecosystems and show how various guilds of free-living nematodes apparently regulate rates of decomposition, thus eventually affecting nutrient cycling processes.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1982-92069</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Gentry, J. B.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Ant communities of southeastern longleaf pine plantations</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1981</style></year></dates><volume><style face="normal" font="default" size="100%">10</style></volume><pages><style face="normal" font="default" size="100%">183-185</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The ant community in a recent replant longleaf pine plantation on the Savannah River Plant, S.C. had the greatest species diversity and richness when compared to mature, thinned and burned pine plantations.  Four species of ants dominated all pine plantations: &lt;i&gt;Crematogaster lineolata&lt;/i&gt; (Say), &lt;i&gt;Aphaenogaster traetae &lt;/i&gt;Forel, &lt;i&gt;Aphaenogaster fulva&lt;/i&gt; Roger and &lt;i&gt;Conomyrma insana&lt;/i&gt; Roger.  There is an apparent relationship between the channelization of stumps, snags and dead logs by termites and densities of &lt;i&gt;Crematogaster&lt;/i&gt; spp.  Recent burning of pine straw had no measurable effect on the dominant tree bole/stump nesting species.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1981-92081</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Shaffer, David T.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Behavioral responses of a predator, the round-tailed horned lizard, &lt;i&gt;Phrynosoma modestum&lt;/i&gt; and its prey, honey pot ants, &lt;i&gt;Myrmecocystus&lt;/i&gt; ssp.</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1981</style></year></dates><volume><style face="normal" font="default" size="100%">105</style></volume><pages><style face="normal" font="default" size="100%">209-216</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The round-tailed horned lizard &lt;i&gt;Phrynosoma modestum&lt;/i&gt; was active and feeding throughout the day from 2 hr after sunrise until sunset.  &lt;i&gt;Phrynosoma modestum&lt;/i&gt; remained in the shade of large mesquite during midday where they preyed on honey pot ants (&lt;i&gt;Myrmecocystus depilis/mimicus&lt;/i&gt;) which were foraging in the canopy and moving across the shaded substrate.  &lt;i&gt;Phrynosoma modestum&lt;/i&gt; fed at an average of 3.9 +- 2.2 ants bout-1 and average of 7.0 +- 1.7 bouts hr-1.  The species diversity of the diet of &lt;i&gt;P. modestum&lt;/i&gt; doubled (H' = 0.78 to H' = 1.41) following rainfall when many species of small ants extended their activity to overlap with the activity of &lt;i&gt;P. modestum.&lt;/i&gt;  Honey pot ants &lt;i&gt;Myrmecocystus mimicus/depilis&lt;/i&gt; were, however, the only dependable prey.  Simulated predation of 20 ants day-1 and 40 ants day-1 affected activity of &lt;i&gt;M. mimicus/depilis&lt;/i&gt; , while simulated predation of 10 ants day-1 had no effect.  We estimate that &lt;i&gt;P. modestum&lt;/i&gt; removes approximately one-half of the early summer standing crop of &lt;i&gt;M. mimicus/depilis&lt;/i&gt; during the summer.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1981-92084</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Freckman, Diana W.</style></author><author><style face="normal" font="default" size="100%">Elkins, Ned Z.</style></author><author><style face="normal" font="default" size="100%">Parker, Lawrence W.</style></author><author><style face="normal" font="default" size="100%">Parmalee, Rob</style></author><author><style face="normal" font="default" size="100%">Phillips, Janice</style></author><author><style face="normal" font="default" size="100%">Tucker, Suzanne</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Diurnal migration and responses to simulated rainfall in desert soil microarthropods and nematodes</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1981</style></year></dates><volume><style face="normal" font="default" size="100%">13</style></volume><pages><style face="normal" font="default" size="100%">417-425</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Diurnal patterns of microarthropod abundance in surface leaf litter were related to its moisture content.  Leaf litter moisture was nearly 7% by weight at 0800 h but fell to less than 1 % by mid-day.  Oribatid and tydeid mites moved into litter in the early morning and back into the soil before mid-day.  There were no significant differences in numbers of nematodes in litter or soil and 78098% of the nematodes were anhydrobiotic (coiled) in soil and litter at all times sampled.     Following simulated rainfall there were fewer microarthropods in litter at mid-day in the absence of marked decreases in soil and litter moisture content.  During drying, there were gradual reductions in numbers and species diversity of litter microarthropods.  Nematode numbers did not change as litter dried.  Anhydrobiotic nematodes in the soil increased from 14% on day 1 to 85% on day 4.  Between 24 and 36 h after simulated rainfall, the proportion of anhydrobiotic litter nematodes increased from 35 to 80%.     Within 1 h after simulated rainfall, there were marked increases in numbers and diversity of microarthropods in surface litter.  No collembolans were extracted from dry litter controls but the wet litter was dominated by isotomid, sminthurid and onychiurid collembolans.  There were increases in numbers and diversity of oribatid, tydeid and gamasid mites in the wet surface litter within 1 h after wetting compared to controls.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1981-92086</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Santos, Perseu F.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">The effects of microarthropods on litter decomposition in a Chihuahuan Desert ecosystem</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1981</style></year></dates><volume><style face="normal" font="default" size="100%">62</style></volume><pages><style face="normal" font="default" size="100%">654-663</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We compared decomposition of surface and buried, untreated, mixed desert shrub litter to that of insecticide- and fungicide-treated litter.  Suppression of fungi reduced decomposition by ~29%; exclusion of microarthropods reduced decomposition by ~53%.  Approximately 55% of the organic mass of the untreated litter disappeared during the 6-mo growing season and 23-29% disappeared in the winter months (November through March).     There was a consistent pattern of microarthropod colonization of buried litter that was related to the percent organic matter lost.  This sequence tydeid mites, trasonemid and pyemotid mites, gamasina and predatory Prostigmata, Collembola and Psocoptera, and oribatids.  After 1 yr, large numbers of enchytraeid worms were extracted from buried litter.  Decomposition of insecticide-treated litter varied directly with rainfall and soil temperature while abiotic factors accounted for &lt;50% of the variation in decomposition of untreated buried litter.  We hypothesize that microarthropods affect litter decomposition in desert ecosystems by inoculating litter with fungal spores, but grazing on fungi, and in a heretofore undescribed mode, by preying on free-living nematodes.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1981-92088</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Wisdom, Wendy A.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Effects of vegetation change on ant communities of arid rangelands</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1981</style></year></dates><volume><style face="normal" font="default" size="100%">10</style></volume><pages><style face="normal" font="default" size="100%">893-897</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We compared the density and diversity of ant colonies on areas where the vegetation had been altered by treatment with herbicides and on untreated areas.  Highest densities of ant colonies were on the untreated mesquite dune habitat and the grassland habitat.  The treated habitats were characterized by differences in shrub cover and composition and cover of forbs and grasses.  &lt;i&gt;Conomyrma bicolor&lt;/i&gt; and &lt;i&gt;Solenopsis xyloni&lt;/i&gt; Were significantly more numerous on the mesquite dunes and grassland, respectively.  The fungus-culturing ant, &lt;i&gt;Trachymyrmex smithi&lt;/i&gt;, was abundant on the treated dune habitats and absent in the grassland habitat.  Ant communities were most similar on the two sites subjected to vegetation modification, and most different comparing those dune habitats with the untreated mesquite dunes.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1981-92089</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Exceptions to the AET model: deserts and clearcut forest.</style></title><secondary-title><style face="normal" font="default" size="100%">Ecology</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">CWT</style></keyword><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1981</style></year></dates><urls><web-urls><url><style face="normal" font="default" size="100%">http://cwt33.ecology.uga.edu/publications/252.pdf</style></url></web-urls></urls><volume><style face="normal" font="default" size="100%">62</style></volume><pages><style face="normal" font="default" size="100%">275-277</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">A model for decomposition of litter as a function of actual evapotranspiration (AET) and lignin content developed for temperate and boreal forest sites was tested for other ecosystems. The correlation between AET and decomposition does not necessarily apply to all vegetation types nor to severely disturbed sites. Decomposition is higher than predicted by the AET Model in deserts where AET is low, and lower than predicted for a mesic clear-cut forest where AET values are higher than uncut forests.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1981-81210</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">DePree, Dirk J.</style></author><author><style face="normal" font="default" size="100%">Hamilton, Patrick</style></author><author><style face="normal" font="default" size="100%">Ettershank, George</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Foraging ecology of seed-harvesting ants, Pheidole spp in a Chihuahuan Desert ecosystem</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1981</style></year></dates><volume><style face="normal" font="default" size="100%">105</style></volume><pages><style face="normal" font="default" size="100%">159-167</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Seasonal activity, factors affecting foraging activity and forage selection were studied in three species of &lt;i&gt;Pheidole&lt;/i&gt; (Hyminoptera: Formicidae) on a watershed in the southern New Mexico Chihuahuan Desert.  &lt;i&gt;Pheidole&lt;/i&gt; spp. exhibited a seasonal pattern in numbers of active colonies with most colonies active in July coincident with onset of summer rains and seed drop by annual plants.  &lt;i&gt;Pheidole militicida&lt;/i&gt; occurred only on the deeper soils of the lower watershed while &lt;i&gt;Ph. rugulosa&lt;/i&gt; and &lt;i&gt;Ph. xerophila&lt;/i&gt; occurred on the entire watershed.  The three &lt;i&gt;Pheidole &lt;/i&gt;spp. were active only at soil temperatures between 15-35C and were most active at sunrise.  Analysis of factors affecting foraging intensity using a stepwise discriminant function and regression showed evaporation and soil surface temperature to be the strongest influences and seed availability to rank second.  However, the factors included in the analysis accounted for less than 50% of the variance in all three species.  &lt;i&gt;Pheidole militicida&lt;/i&gt; collected mostly forb seeds while &lt;i&gt;Ph. xerophila&lt;/i&gt; utilized primarily grass seeds, especially the seeds of fluff grass &lt;i&gt;Erioneuron pulchellum&lt;/i&gt;.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1981-92094</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Santos, Perseu F.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Litter decomposition in the desert</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1981</style></year></dates><volume><style face="normal" font="default" size="100%">31</style></volume><pages><style face="normal" font="default" size="100%">145-146</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Since significant quantities of plant litter are buried by wind and water in this desert, we designed studies to address the following questions:  What are the relative contributions of bacteria, fungi, and microarthropods to litter decomposition?  Is there a pattern of microarthropods succession related to the stage of litter decomposition?  What are the differences in buried and surface litter decomposition?     The initial stages of buried litter decomposition appears to be via bacteria, which are grazed upon by nematodes.  Removal of the nematode predator apparently allowed nematodes to overgraze the bacteria, reducing their population size and reducing decomposition.  Without predators, grazers appear to be detrimental to decomposition, as has been suggested by Hanlon and Anderson (1979).  Thus, in desert ecosystems, microarthropods affect litter decomposition by a heretofore undescribed mode: preying on free-living nematodes.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1981-92098</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Fowler, Harold G.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Mating behavior of Polyphylla diffracta (Coleoptera: Scarabaeidae)</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1981</style></year></dates><volume><style face="normal" font="default" size="100%">26</style></volume><pages><style face="normal" font="default" size="100%">215-216</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">On 26 Jul. 1969, imagos were observed emerging form an open park near Las Cruces, New Mexico, between 1800 and 2000 h (MST).  Males were flying in a zig-zag pattern, 10 to 50 cm above ground level, with their lamellate antennae extended.  In three of the 22 copulations observed, males helped the female to dig her way out of the soil.  Females emerged briefly, mated, than returned to their emergence burrows and disappeared.  Only males were captured at lights, suggesting that females emerge only to mate.  On 16 occasions, more than one male was attracted to the emergence hole, resulting in jostling for copulatory positions.  After on male successfully engaged the female genitalia, the other males dispersed.  Three newly emerging females were captured before copulation and placed in small screen cages.  When placed on the ground, each of these cages attracted a minimum of five males within a 5-min time period.  Males also landed and investigated emergence holes into which newly mated females had returned.  All of these observations support the presence of sex pheromones in &lt;i&gt;Polyphylla diffracta&lt;/i&gt;, and suggest that the females mate only once.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1981-92101</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Schaefer, Douglas A.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Nutrient cycling by the subterranean termite &lt;i&gt;Gnathamitermes tubiformans&lt;/i&gt; in Chihuahuan Desert ecosystem</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1981</style></year></dates><volume><style face="normal" font="default" size="100%">48</style></volume><pages><style face="normal" font="default" size="100%">277-283</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We estimated the density of subterranean termites &lt;i&gt;Gnathamitermes tubiformans&lt;/i&gt; at 800,000 ha-1 for a standing crop biomass of 2 kg ha-1.  Predation losses were estimated to be 5.73 kg ha-1 yr-1 representing the major release of nutrients from termites to surficial soil layers.  Nutrient fluxes from termites to predators amounted to 410 g N ha-1 yr-1, 33 g S ha-1 yr-1 and 19 g P ha-1 yr-1.  These fluxes account for 8% of the litter N, 1.5% of the litter P and 2.9% of the litter S.  The termites fixed an estimated 66 g ha-1 yr-1 atmospheric N and returned an estimated 100 g ha-1 yr-1 in the surface gallery carton.  Since losses of elements from subterranean termites were greater than standing crops, we estimated an annual turnover of N at 3.5 times per year, P of 2.5 times per year, and S of 2.5 per times per year.     Since surface foraging, predation and alate flights are pulse regulated by rainfall, nutrient flows through subterranean termites are episodic and releases of nutrients accumulated in termite biomass preceeds or is coincident with productivity &quot;pulses&quot; of some shallow rooted plants.  We propose that subterranean termites are important as regulators in desert nutrient cycles.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1981-92102</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Santos, Perseu F.</style></author><author><style face="normal" font="default" size="100%">Phillips, Janice</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">The role of mites and nematodes in early stages of buried litter decomposition in a desert</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1981</style></year></dates><volume><style face="normal" font="default" size="100%">62</style></volume><pages><style face="normal" font="default" size="100%">664-669</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We studied changes in populations of mites, nematodes, bacteria, and fungi in buried creosote bush litter treated with selected inhibitors.  Elimination of microarthropods (primarily tydeid mites) resulted in increased numbers of bacteriophagic nematodes and reduction in numbers of bacteria; elimination of both nematodes and microarthropods resulted in increased numbers of bacteria compared to untreated controls.  Fungal grazing mites, Pyemotidae, and funivourous nematodes, &lt;i&gt;Aphelenchus&lt;/i&gt; sp., increased in numbers between days 25 and 30, reducing the fungi on untreated leaves but not on stems and petioles, while mean length of fungal hyphae increased in insecticide-treated leaves.  Elimination of mites resulted in a 40% reduction in decomposition suggesting that in a desert, tydeid mites affect decomposition of buried litter by regulating the population size of the bacterial grazers, cephalobid nematodes.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1981-92114</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>6</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Ludwig, J. A.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors><secondary-authors><author><style face="normal" font="default" size="100%">with the assistance of K. M. W. Howes (eds.),</style></author></secondary-authors></contributors><titles><title><style face="normal" font="default" size="100%">Short-term water and energy flow in arid ecosystems</style></title><secondary-title><style face="normal" font="default" size="100%">Arid Land Ecosystems: Structure, Function and Management</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1981</style></year></dates><publisher><style face="normal" font="default" size="100%">Cambridge University Press</style></publisher><pub-location><style face="normal" font="default" size="100%">Great Britain</style></pub-location><volume><style face="normal" font="default" size="100%">2</style></volume><pages><style face="normal" font="default" size="100%">271-299</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The objective of this chapter is to discuss the dynamic behavior of the biotic components of arid ecosystems in relation to water and energy flow between and within seasons.  The growth responses of the different plant species occupying adjacent ecosystems in a watershed will be related to water availability and to heat energy levels.  Growth and behavioral responses of groups of animals with contrasting adaptations to changing conditions of food and water availability will be discussed.  Plant and animal litter redistribution and decomposition patterns will be discussed with respect to patterns of energy flow and climatic variation.  Finally, general conclusions about desert ecosystem dynamics with respect to short-term water and energy flow will be stated.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1981-92116</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">DePree, E.</style></author><author><style face="normal" font="default" size="100%">Johnson, P.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Foraging ecology of two Chihuahuan Desert ant species: Novomessor cockerelli and Novomessor albisetosus</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1980</style></year></dates><volume><style face="normal" font="default" size="100%">27</style></volume><pages><style face="normal" font="default" size="100%">148-156</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">&lt;i&gt;Novomessor albisetosus&lt;/i&gt; and &lt;i&gt;N. cockerelli&lt;/i&gt; foraged most intensively in the evening and morning at soil surface temperatures between 20 C and 40 C.  They were not active in the middle of the night and mid-day.  In both species, colonies provided with supplementary seeds increased their foraging intensity.  &lt;i&gt;N. cockerelli&lt;/i&gt; colonies which were provided with high protein food (tuna fish) extended their foraging time and remained active until soil surface temperatures reached lethal levels.  Nearly half of the natural forage of  &lt;i&gt;N. cockerelli&lt;/i&gt; was insects or insect parts which accounted for only 6.6% of the forage of &lt;i&gt;N. albisetosus&lt;/i&gt;.  Approximately 10% of the workers of &lt;i&gt;N cockerelli&lt;/i&gt; entered and were apparently accepted by colonies other then their &quot;home&quot; colony.  This study demonstrates the importance of both forage availability and forage quality as determinants of activity and forage selection of &lt;i&gt;Novomessor&lt;/i&gt; sp.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1980-92143</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Ettershank, G.</style></author><author><style face="normal" font="default" size="100%">Ettershank, J. A.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Location of food source by subterranean termites</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1980</style></year></dates><volume><style face="normal" font="default" size="100%">9</style></volume><pages><style face="normal" font="default" size="100%">645-648</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Chihuahuan desert subterranean termites, &lt;i&gt;Gnathamitermes tubiformans&lt;/i&gt; (Buckley) and &lt;i&gt;Amitermes wheelerii&lt;/i&gt; (Desneux) readily located surface foods but failed to utilize buried foods of the same type.  The termites attacked both natural cowdung pats and artificial (polyurethane) cowdung pats at the same rate as estimated by holes chewed through plastic film barriers placed between the soil and both kinds of pats.  There was smaller diel excursion of temperatures in the upper 20 cm of soil under dungpats than in the soil not under dung.  We suggest that desert subterranean termites locate relatively large size surface foods such as cattle dung and Yucca sp. logs by sensing the thermal shadows cast by such items.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1980-92151</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author><author><style face="normal" font="default" size="100%">Bryant, Martha</style></author><author><style face="normal" font="default" size="100%">Ettershank, George</style></author><author><style face="normal" font="default" size="100%">Ettershank, Jennifer</style></author><author><style face="normal" font="default" size="100%">Santos, Perseu F.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Surface litter breakdown in a Chihuahuan Desert ecosystem</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1980</style></year></dates><volume><style face="normal" font="default" size="100%">20</style></volume><pages><style face="normal" font="default" size="100%">243-245</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">In a study of distribution patterns of litter and microarthropods we (Santos et al. 1978) found that microarthropod density was highly correlated with amount of surface litter in a Chihuahuan desert creosotebush community.  Based on that relationship we hypothesized that the rate of litter decomposition would vary directly with the amount of surface litter present.  This paper reports on experiments designed to test that hypothesis and to examine the relationship between quantity of surface litter, microarthropod density and plant growth.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1980-92167</style></accession-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Fowler, Harold G.</style></author><author><style face="normal" font="default" size="100%">Whitford, W. G.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Termites, microarthropods and the decomposition of senescent and fresh creosotebush (Larrea tridentata) leaf litter</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">JRN</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1980</style></year></dates><volume><style face="normal" font="default" size="100%">3</style></volume><pages><style face="normal" font="default" size="100%">63-68</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Weight loss of fresh and senescent creosotebush (&lt;i&gt;Larrea tridentata&lt;/i&gt;) leaves was studied during September and October, which is normally the peak of surface feeding by subterranean termites.  Termites built galleries in 87.5 per cent of the bags of senescent litter and in 12.5 per cent of the bags of fresh litter.  There was no significant weight loss attributable to termites.  Senescent litter lost more weight than fresh litter but this was reversed during a period of abnormally high rainfall.  It is suggested that this results from the presence of allelochemics in fresh litter and leaching of these compounds with high precipitation.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1980-92168</style></accession-num></record></records></xml>