<?xml version="1.0" encoding="UTF-8"?><xml><records><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%">Reynolds, J. F.</style></author><author><style face="normal" font="default" size="100%">Kemp, P. R.</style></author><author><style face="normal" font="default" size="100%">Ogle, K.</style></author><author><style face="normal" font="default" size="100%">Fernandez, R. J.</style></author><author><style face="normal" font="default" size="100%">Gao, Q.</style></author><author><style face="normal" font="default" size="100%">Wu, J.</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%">Modeling the unique attributes of aridland ecosystems: Lessons from the Jornada Basin</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/06-067.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%">321-353</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The Jornada Basin is typical of aridland ecosystems of the southwestern United States and many other regions of the globe: it is water-limited with low annual net primary production (ANPP) and low-standing crop (Szarek 1979; Ludwig 1987). Yet, paradoxically, aridland ecosystems are structurally and functionally quite complex, exhibiting a remarkable range of species compositions and system behaviors. This can be attributed, in part, to the presence of complex topography and landscape physiography which, when combined with extreme variability in precipitation, produces striking spatial and temporal heterogeneity in the availability of essential limiting resources such as water and mineral nutrients.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2006-90498</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%">Reynolds, J. F.</style></author><author><style face="normal" font="default" size="100%">Kemp, P. R.</style></author><author><style face="normal" font="default" size="100%">Ogle, K.R.</style></author><author><style face="normal" font="default" size="100%">Fernandez, R. J.</style></author><author><style face="normal" font="default" size="100%">Gao, Q.J.</style></author><author><style face="normal" font="default" size="100%">Wu, J.J.</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%">Modeling the unique attributes of dryland ecosystems</style></title><secondary-title><style face="normal" font="default" size="100%">Structure and function of a Chihuahuan Desert ecosystem</style></secondary-title></titles><keywords><keyword><style  face="normal" font="default" size="100%">CAP</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2006</style></year></dates><publisher><style face="normal" font="default" size="100%">Oxford University Press</style></publisher><pages><style face="normal" font="default" size="100%">321-353</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><accession-num><style face="normal" font="default" size="100%">LTER.2006-93053</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%">Reynolds, J. F.</style></author><author><style face="normal" font="default" size="100%">Maestre, F.T.</style></author><author><style face="normal" font="default" size="100%">Huber-Sanwald, E.</style></author><author><style face="normal" font="default" size="100%">Herrick, J. E.</style></author><author><style face="normal" font="default" size="100%">Kemp, P. R.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Aspectos Socioeconomicos Y Biofisicos de la Desertificaction</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/05-019.pdf</style></url></web-urls></urls><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Land degradation and desertification are among the most important environmental issues being faced by drylands. Despite its importance and the enormous research effort devoted to it in the last decades, desertification is a topic surrounded by controversy and disagreement. This controversy is rooted in the traditional separation of the biophysical and socio-economic dimensions of desertification, which have been studied separately by scientists from both the natural and the social sciences. This separation has been fueled by the lack of a conceptual and synthethic framework suited to deal with both dimensions simultaneously. In this article we review the main topics surrounding desertification, introduce a new conceptual framework designed to study the biophysical and socio-economic dimensions of desertification simultaneously, review some of the measures being carried out to manage desertified lands and discuss some of the main challenges ahead in the research and management arenas.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2005-90575</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%">Shen, W.</style></author><author><style face="normal" font="default" size="100%">Wu, J.</style></author><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%">Grimm, N.B.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Simluating the dymanics of primary productivity of a Sonoran ecosystem: Model parameterization and validation</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">CAP</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">2005</style></year></dates><volume><style face="normal" font="default" size="100%">189</style></volume><pages><style face="normal" font="default" size="100%">1-24</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><accession-num><style face="normal" font="default" size="100%">LTER.2005-93068</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>5</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Reynolds, J. F.</style></author><author><style face="normal" font="default" size="100%">Fernandez, R. J.</style></author><author><style face="normal" font="default" size="100%">Kemp, P. R.</style></author></authors><secondary-authors><author><style face="normal" font="default" size="100%">Komanine, A. (eds.)</style></author></secondary-authors></contributors><titles><title><style face="normal" font="default" size="100%">Drylands and global change: Rainfall variability and sustainable rangeland production</style></title><secondary-title><style face="normal" font="default" size="100%">Proceedings of the 12th Toyota Conference: Challenge of Plant and Agricultural Sciences to the Crisis of the Biosphere on the Earth in the 21&lt;sup&gt;st&lt;/sup&gt; Century</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%">2000</style></year></dates><publisher><style face="normal" font="default" size="100%">R. G. Landes Company</style></publisher><pub-location><style face="normal" font="default" size="100%">Austin, Texas</style></pub-location><pages><style face="normal" font="default" size="100%">73-86</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">This chapter reviews the extent of global change in drylands and some of its ecological and societal consequences. It also discusses rainfall variability as one component of potential climate change and how it affects primary production in rangelands. This is illustrated with a case study of a rangeland in southern New Mexico using a physiologically-based ecosystem model. It suggests that basic ecological knowledge should be an essential component of assessment frameworks.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2000-91158</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%">Reynolds, J. F.</style></author><author><style face="normal" font="default" size="100%">Kemp, P. R.</style></author><author><style face="normal" font="default" size="100%">Tenhunen, J. D.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Effects of long-term rainfall variability on evapotranspiration and soil water distribution in the Chihuahuan Desert: A modeling analysis</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><volume><style face="normal" font="default" size="100%">150</style></volume><pages><style face="normal" font="default" size="100%">145-159</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We used the patch arid land simulator (PALS-FT) -- a simple, mechanistic ecosystem model -- to explore long-term variation in evapotranspiration (ET) as a function of variability in rainfall and plant functional type (FT) at a warm desert site in southern New Mexico.  PALS-FT predicts soil evaporation and plant transpiration of a canopy composed of five principal plant FTs: annuals, perennial forbs, C&lt;sub&gt;4&lt;/sub&gt; grasses, sub-shrubs, and evergreen shrubs.  For each FT, the fractional contribution to transpiration depends upon phenological activity and cover as well as daily leaf stomatal conductance, which is a function of plant water potential, calculated from root-weighted soil water potential in six soil layers.  Simulations of wat6er loss from two plant community types (grass- vs. shrub-dominated) were carried out for the Jornada Basin, New Mexico, using 100 years of daily precipitation data (1891-1990).  In order to emphasize variability associated with rainfall and fundamental differences in FT composition between communities, the seasonal patterns cover of perennials were held constant from year to year.  Because the relative amount of year to year cover of winter and summer annual species is highly variable in this ecosystem, we examined their influence on model predictions of ET by allowing their cover to be variable, fixed, or absent.      Over the entire 100-yr period, total annual ET is highly correlated with total annual rainfall in both community types, although T and E alone are less strongly correlated with rainfall, and variation in transpiration is nearly 3 times greater than evaporation and 2 times greater than variation in rainfall (CV of rainfall = 35%).  Water use shows a relatively high similarity between the grass- and shrub-dominated communities, with a 100-yr average T/ET of 34% for both communities.  However, based on a year-by-year comparison between communities, T/ET was significantly greater in the grass-dominated community, reflecting the fact that over the long term more than half of the rain occurs in the summer and is used slightly more efficiently (T&gt;E) by the C&lt;sub&gt;4&lt;/sub&gt;-grass community than the shrub community, although we found some rainfall patterns that resulted in much greater T/ET in the shrub community in a given year.  Percent of water lost as transpiration (T/ET) suggests that while there is a general trend toward increased T/ET with rainfall in both community types, T/ET is extremely variable over the 100-yr simulation, especially for normal and below normal amounts of rainfall (T/ET values range from 1 to 58% for the grass-dominated site and 6 to 60% for the shrub-dominated site).      These predictions suggest that because of the relatively shallow distribution of soil water, there is little opportunity for vertical partitioning of the soil water resource by differential rooting depths of the plant FTs.  However, functional types may avoid competition by keying on particular &quot;windows&quot; of moisture availability via differences in phenologies.  We found very little differences in average, long-term model predictions of T, E, and ET when annual plant cover was variable, fixed, or absent.  The results of our simulations help reconcile some of the disparate conclusions drawn from experimental studies about the relative contribution of transpiration vs. evaporation to total evapotranspiration, primarily by revealing the great year-to-year variability that is possible.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.2000-91159</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%">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%">Kemp, P. R.</style></author><author><style face="normal" font="default" size="100%">de Soyza, A. G.</style></author><author><style face="normal" font="default" size="100%">Tremmel, D. C.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Impact of drought on desert shrubs: Effects of seasonality and degree of resource island development</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/680.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%">69-106</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Large areas of semiarid grasslands in the southwestern United States have been virtually replaced by shrubs during the past century.  Understanding the causes and consequences of such vegetation dynamics requires that we elucidate the interplay between external forces of change (e.g., climate, human impacts) and the internal forces within these ecosystems that foster resilience and/or stability. Several conceptual models of and ecosystems address this interplay by including the potential role of autogenic shrub effects on ecosystem processes that lead to the formation of &quot;resource islands&quot; and tend to promote shrub persistence.  Specifically, during the process of shrub establishment and maturation, the cycling of nutrients is progressively confined to the zones of litter accumulation beneath shrubs, while bare intershrub spaces become increasingly nutrient poor.  As shrub resource islands develop, there is increased interception and stemfiow by shrub canopies, confining infiltration of nutrient-enriched rainfall directly beneath the shrubs; the barren intershrub spaces generate overland flow, soil erosion by wind and water, and nutrient losses.  These islands are preferred sites for the regeneration of shrubs and herbaceous plants and are correlated with spatial variation in soil microbial populations and soil microfauna that promote nutrient cycling.  If further changes in the transition between grassland and shrubland are to be correctly predicted, or if we wish to intervene and redirect transitions, we must develop a greater mechanistic understanding of the structural and functional relationships between shrubs and the resource islands associated with them.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1999-91195</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%">Pachepsky, Y.</style></author><author><style face="normal" font="default" size="100%">Chen, J. -L.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">A comparative study of soil water dynamics 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%">1997</style></year></dates><volume><style face="normal" font="default" size="100%">33</style></volume><pages><style face="normal" font="default" size="100%">73-90</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><accession-num><style face="normal" font="default" size="100%">LTER.1997-91334</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%">Freas, K.E.</style></author><author><style face="normal" font="default" size="100%">Kemp, P. R.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Some relationships between enviornmental relaibility and seed dormancy in 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%">1983</style></year></dates><volume><style face="normal" font="default" size="100%">71</style></volume><pages><style face="normal" font="default" size="100%">211-217</style></pages><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">(1) There are two groups of annual species that grow in the northern Chihuahuan Desert of North America.  Plants in one group germinate and complete their life cycle in late summer.  Those in the other germinate in winter or early spring and complete their life cycle in the spring.  The late summer season in characterized by abundant and reliable rain, while the winter-spring season has less abundant and less reliable rain.     (2) Several theoretical models have been suggested which predict that annual plants from uncertain environments may or may not have evolved innate dormancy to offset the possibility of population extinction due to complete germination followed by complete mortality under severely unfavourable conditions.     (3) We have tested these models with a comparative experiment examining the germination responses of seeds collected from an annual species which grows during the more reliable summer season and two annual species which grow during the less reliable winter-spring season.     (4) The summer annual species does not have a genetically fixed innate dormancy, but the two winter annual species apparently have evolved a genetically controlled innate dormancy.      (5) All three annual species exhibited environmentally-controlled seed dormancy with respect to amount of rainfall.  Seeds germinated only when the equivalent of more than 10 mm of rain fell.  Above 15 mm of simulated rain, germination was positively correlated with increasing amount of rain in all three species.     (6) The importance of innate dormancy, water-controlled dormancy, and seed dispersal to the long-term survival of these species is discussed.</style></abstract><accession-num><style face="normal" font="default" size="100%">LTER.1983-92034</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%">Williams, GJ</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">A physiological basis forniche separation between Agropyron smithii (C3) and Bouteloua gracilis (C4)</style></title></titles><keywords><keyword><style  face="normal" font="default" size="100%">SGS</style></keyword></keywords><dates><year><style  face="normal" font="default" size="100%">1980</style></year></dates><volume><style face="normal" font="default" size="100%">61</style></volume><pages><style face="normal" font="default" size="100%">846-858</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.1980-69032</style></accession-num></record></records></xml>