	2003 LTER ASM
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35-Year Response of Interior Alaska Forest Types to Thinning and Fertilization

Date Presented: Friday Night

Lead Author: John Yarie
Co-Authors: Keith Van Cleve
Institutional Affiliations: University of Alaska Fairbanks
Primary Site: BNZ

Abstract: Seven long-term studies on tree growth dynamics were monitored during the past 35 years. At the individual tree level the young aspen stands were nitrogen limited but this limitation decreased as the stand aged. Birch in most studies showed no nutrient limitation, but increased growth was reported after a thinning treatment was applied. In white spruce stands, the trees showed growth increases for 28 years after the combined thinning and fertilization treatments were applied. Annual low-level fertilization in the LTER sites started to show significant growth increases 10 years after the fertilization treatments were started. The drought treatments decreased growth on the floodplain sites with relatively little change in upland sites. The complexity of ecosystem dynamics across the landscape is related to a differential structure and interaction of the process limiting factors. Fertilization may only increase tree growth if other major limiting factors (such as moisture) are satisfied. So a direct change in that factor, like irrigation in a dry environment, should increase growth up to the limit set by the next environmental factor, say nitrogen. However a change in the potential amplitude of a limiting factor, like thinning a forest stand to reduce the total water utilization on a site (an indirect change related to the limiting factor availability), may not augment the control of growth with comparable effectiveness that would be observed by irrigation (a direct change in the limiting factor availability). In the case of a forest stand a large number of growth limiting factors could be diminished as a result of thinning. Factors like nutrient availability would be increased as a result of reduced competition, greater site utilization by the remaining individual trees, and possibly increased nutrient turnover in the soil environment. These factors may require several years to produce an increase in growth in the remaining trees.

A comparative study of native and introduced Phragmites australis haplotypes in Virginia

Date Presented: Saturday Night

Lead Author: Thomas J. Mozdzer
Co-Authors: Joseph C. Zieman
Institutional Affiliations: Univeristy of Virginia
Primary Site: VCR

Abstract: The common reed, Phragmites australis, is thought by some to be the most widely distributed flowering plant in the world. On the Virginia Coast Reserve/LTER site, Phragmites australis expansion is of great concern as it establishes itself into previously unoccupied habitats. Recent genetic research has identified eleven native haplotypes and one introduced haplotype in North America. Two haplotypes are present in Virginia, type F, which is endemic to Virginia and Maryland only, and the introduced, haplotype M. The cryptic invasion of the introduced haplotype M, is thought to be responsible for the expansion of Phragmites australis in North America. No research to date has comparatively studied any Phragmites australis haplotypes. To investigate possible differences between Phragmites australis haplotypes F and M, shoots and their associated roots were sampled from genetically identified populations, which were grown in the greenhouse under field conditions. Short-term responses to a range of salinity levels and photosynthetic efficiency were measured in laboratory experiments. This study aims to determine if physiological differences exist between the native haplotype F, and the introduced haplotype M of Phragmites australis. These results may help elucidate the distribution and the expansion of this plant in Virginia and other Mid-Atlantic states.

A complex of ecophysiological behaviors in dominant shrubs on the Jornada LTER, emphasizing Larrea tridentata

Date Presented: Friday Night

Lead Author: Vincent P. Gutschick¹
Co-Authors: Hormoz BassiriRad², Randall Fowler¹, Anna Linnell¹, Carla Logan¹,Connie Maxwell³,
Institutional Affiliations: New Mexico State University¹, University of Illinois at Chicago², USDA-ARS, Jornada Experimental Range³
Primary Site: JRN

Abstract: Shrubs have expanded their coverage markedly on the Jornada LTER in historic times. Their ability to restructure resources physically has been a focus on Jornada research. In our work, we examine a variety of physiological attributes contributing to shrub success, particularly the attributes of creosotebush, Larrea tridentata: (1) the dynamics of retention and recovery in both leaf area and photosynthetic capacity; (2) mechanisms of protection of cambium from extreme high soil temperatures at stem bases; (3) stomatal control for water use regulation and water-use efficiency; (4) hydraulic redistribution by roots, making effective use of deep soil as a water reserve; and (5) tissue N reserves, especially for shoot regrowth after major losses. We have begun a synthesis of the role of such behavior in physiological, ecological, and evolutionary changes wrought by extreme events, notably climatic extremes.

A computer model for the management of fuels, human-fire interactions, and wildland fires in the boreal forest of Alaska

Date Presented: Friday Night

Lead Author: T. Scott Rupp
Co-Authors: D.H. Mann and P. Duffy
Institutional Affiliations: University of Alaska Fairbanks
Primary Site: BNZ

Abstract: Fire management issues are growing in importance as human populations progressively expand into former roadless areas. The same natural fire regimes (i.e., fire frequency, intensity and size) that underlie the structure and function of many wildland areas also threaten human life and property. In many parts of North America, the build-up of wildland fuels caused by fire management activities over the past 50-100 years have increased the dangers posed by wildland fires. Fuel build-up–either in the form of dead, woody debris or, as is the case in interior Alaska, increasing continuity of flammable forest cover– is undesirable for two reasons. First, it can cause future catastrophic wildland fires; second, it may cause changes in the natural fire regime that adversely affect flora and fauna. An understanding of the processes that control wildland fuel accumulation, including the role that fire management activities play, is crucial for designing wildland management policies. We developed a spatially explicit model, called Boreal ALFRESCO, which simulates the responses of subarctic and boreal vegetation to transient climatic changes. The model assumptions reflect the hypothesis that fire regime and climate are the primary drivers of landscape-level changes in the distribution of vegetation in the circumpolar arctic/boreal zone. Furthermore, it assumes that vegetation composition and continuity serve as a major determinant of large, landscape-level fires. Boreal ALFRESCO operates on an annual time step, in a landscape composed of 1 x 1 km pixels, a scale appropriate for interfacing with mesoscale climate and carbon models. The model simulates five major subarctic/boreal ecosystem types: upland tundra, black spruce forest, white spruce forest, deciduous forest, and grassland-steppe. These ecosystem types represent a generalized classification of the complex vegetation mosaic characteristic of the circumpolar arctic and boreal zones of Alaska.

A Methodology for Estimating Spatial Non-stationarity in Ecosystem Service Valuation

Date Presented: Friday Night

Lead Author: Austin Troy
Co-Authors: Morgan Grove
Institutional Affiliations: University of Vermont, USDA Forest Service
Primary Site: BES

Abstract: We conducted a hedonic analysis of housing transactions in West Baltimore to determine whether there is spatial variability in willingess to pay for proximity to trees and parks, using geographically weighted regression (GWR). GWR is a regression method that allows parameter estimates and test statistics to vary continuously over space. By enabling statistical models to vary over space, we can visualize spatial patterns in complex socio-economic relationships and use this information to help delineate functional socio-economic “patches.” We find that valuations of tree cover and proximity to parks is spatially non-stationary within the study area.

A model for applying ecological knowledge in the school system

Date Presented: Friday Night

Lead Author: Noa Avriel-Avni
Co-Authors: Dalia Arad
Institutional Affiliations: Ramon Science Center, Kaye college
Primary Site: INT

Abstract: Ecological understanding is a condition for wisely managing our relationship with our ecosystem. Long term ecological research, at the LTER sites develops a basis for ecological understanding. However, this knowledge is not always available for pupils and non-ecologists. The purpose of our study is to develop a model for making long term ecological research accessible to pupils and ordinary citizens. The ecological system chosen to develop the model is the loessial valley, in the Negev, Israel. This system is common in much of the desert of Israel and is therefore accessible to many students. Dynamic processes of loss deposition and erosion dramatically affect all aspects of the system, and humans, as well. This system has been studies extensively from many aspects (ecology, geomorphology, hydrology, archaeology, anthropology and other disciplines) and thus much knowledge has accumulated. Our model consists of four components: 1. Description of the whole system, using system terminology. 2. Transformation of scientific knowledge to a form accessible to pupils. 3. Principles to develop a curriculum based on inquiry of complex systems. 4. Computer based environment to support the previous components. We believe that our model can be transferred to other ecosystems and can be used to convey ecological understanding attained at the LTER sites to students and other individuals.

A Strategy for Determining the Physiological Potential of Uncultivated Soil Bacteria

Date Presented: Saturday Night

Lead Author: Kristin Huizinga
Co-Authors: J.L. Rodrigues, B.P. Keough, J.A. Breznak, and T.M. Schmidt
Institutional Affiliations: Michigan State University
Primary Site: KBS

Abstract: Soil harbors approximately 10^9-10^10 bacterial cells per gram of soil, however only about 1% of these cells have been cultured at this time. Without pure cultures it is difficult to assess the physiological potential and impact these microorganisms have in the soil environment. The creation of a bacterial artificial chromosome (BAC) library is a molecular method used to capture genomic DNA in microbially diverse environments. The genomic content of organisms in environmental samples can be analyzed which yields new insight into their in situ metabolic capabilities. BAC vectors can accommodate large pieces (100-500 kb) of DNA, but until now, there has not been a way to preferentially capture phylogenetically useful information (i.e., rRNA gene sequences) linked to genes indicating an organisms physiological potential. A unique BAC vector, pSuperPhyloBAC, has been constructed that contains an I-CeuI restriction site. I-CeuI is an intron-encoded endonuclease that cuts within the 23S rRNA gene of most bacteria. A cloning strategy has been developed that would allow genomic DNA that has been cut with I-CeuI to be inserted into pSuperPhyloBAC. Due to the high degree of conservation in bacterial rRNA operons, this will allow for the creation of a unique BAC library in which each clone would contain a partial 23S rRNA gene and a complete 16S rRNA gene. This library will allow for rapid screening of clones to isolate those containing DNA from microbial groups of interest along with genes indicating their physiological potential. This library will allow us to begin to bridge the gap between phylogeny and function in an environment with few members in pure culture.

Active Layer Freeze/Thaw in the Hyporheic Zones of Streams in the McMurdo Dry Valleys, Antarctica

Date Presented: Saturday Night

Lead Author: Karen Cozzetto
Co-Authors: Diane McKnight, Peter Conovitz
Institutional Affiliations: University of Colorado-Boulder
Primary Site: MCM

Abstract: The hyporheic zone is comprised of soils below and next to a stream through which stream water flows in and out. Flow through this zone affects the biogeochemistry of both the stream and the hyporheic zone by fostering the exchange of nutrients and other solutes between them. Water storage in this zone can affect the hydrologic budget of an ecosystem, particularly one as sensitive to liquid water as the polar desert ecosystem of the McMurdo Dry Valleys, Antarctica. In polar regions, the shape and dimensions of the hyporheic zone are controlled by the seasonal freezing and thawing of the uppermost layer of soils, which lie above permafrost and are known as the active layer. Active layer freeze/thaw makes the hyporheic zone both temporally and spatially dynamic. During the 2002-2003 field season, preliminary investigations into active layer freeze/thaw around Dry Valley streams were done by making weekly active layer depth measurements on transects across several streams. Evidence from these transects indicates that: (1) The presence of snow inhibited active layer thawing. After the snow melted though, the active layer increased in depth by 9-10 cm within a 48-hour period. (2) Stream water temperature appeared to influence active layer thaw, either inhibiting it, in the case of colder water, or enhancing it in the case of warmer water. (3) Steep bank slopes seemed to have deeper active layer thaw than flatter surfaces. (4) The bottom of the active layer started freezing before the top of the active layer.

Activities, experiences, and products of the Coweeta Schoolyard LTER Program, 1998 to 2003

Date Presented: Friday Night

Lead Author: Susan Steiner
Co-Authors: Brian D. Kloeppel
Institutional Affiliations: University of Georgia
Primary Site: CWT

Abstract: This program provides formal instruction, field research experience, and data summary and analysis experiences to K-16 students and instructors using Coweeta Long-term Ecological Research (LTER) projects as a model. The types of activities include assisting scientists with current research projects such as the leaf productivity measurement on the terrestrial gradient plots, overland water flow measurement for the riparian zone restoration project, and tree stem respiration measurements for the carbon flux component of the LTER Regionalization project. Other activities have been custom designed to minimize the “bigfoot" effect on our long term research sites. These activities provided students and teachers with optimal research experience emphasizing data collection and analysis techniques that dovetail into current projects. These custom activities include a remeasurement of tree size at a long term research site in the Joyce Kilmer Old Growth Forest in western North Carolina. During a week long intersession of the Rabun Gap Nacoochee School in Rabun Gap, Georgia, students and teachers assisted scientists remeasuring 350 trees. Three study sites were established in 1995 that included cove, mid-slope, and ridge habitats. The participants learned techniques of plot layout, field identification of trees, and tree measurement. Teachers and leaders from the school also included interdisciplinary curricula such as journal writing, historical literature, math and statistical analysis skills. This multidisciplinary approach partnered Coweeta scientists with the Rabun Gap Nacoochee School Environmental Stewardship Program for a week of productive science activities for both groups. The Coweeta Schoolyard LTER Program acknowledges funding since 1998 from annual supplement grants from the National Science Foundation.

Agricultural Landscapes in Southwest Michigan: 200 Years of Transition

Date Presented: Saturday Night

Lead Author: Alan Rudy
Co-Authors: Craig Harris, Brian Thomas, Siena Kaplan, Michelle Worosz, Maya McCoy
Institutional Affiliations: Michigan State University
Primary Site: KBS

Abstract: Studies of changes in land use often focus on transitions between major categories of forested, agricultural, and residential. We propose that it is equally important to understand transitions within those categories. In this project we focus on the introduction, spread, and abandonment of agriculture in southwest Michigan, and ask how political economy, culture and biogeography have combined to produce a series of transformations in agricultural land use. The environmental and social history of the region has been divided into six time periods. The first period, from 1850 to 1898, was a time of agricultural settlement. The second period, from 1898 to 1919, was a time of agricultural prosperity. The agricultural depression defined the third period, which lasted from 1919 to 1940. Agriculture in southwestern Michigan from 1940 to 1973 consisted of significant modernization and a shift towards Fordist agriculture. The fifth period, from 1973 to 1989, was marked by the first oil shock and declining agricultural profits. The sixth and final period is a time of globalization, diversification, and restructuring. The southwest Michigan region consists of 18 counties surrounding the Kellogg Biological Station. Ecological and socioeconomic data for the region from 1850 until the present have been collected. Particular attention will be paid to the ways in which farm animals mediate the relationships between agriculture and environment. By tracing land use and environmental change over a long time period, this project will identify the integrated, systemic relationship between political economic changes and ecological trends. Furthermore, this project will demonstrate how patterns of change are best understood through an interdisciplinary approach involving both social and natural science perspectives.

Agricultural Landscapes in Transition: A Cross-Scale Approach.

Date Presented: Friday Night

Lead Author: Charles L. Redman
Co-Authors: Ann P. Kinzig, David R. Foster, Myron P Gutmann, Peter M. Kareiva, and Lauren H. Kuby.
Institutional Affiliations: Arizona State University, Arizona State University, University of Michigan, The Nature Conservancy, and Arizona State University
Primary Site: CAP

Abstract: This interdisciplinary, cross-site project is tracing the effects of the introduction, spread, and abandonment of agriculture at six LTER sites. Many current conceptualizations of agrarian transformations assume a simple linear model-change driven by present-day economic, demographic, and technological conditions. This project incorporates a more integrated and long-term cycle: land-use change affecting landscapes, altered landscapes affecting ecological processes, and both influencing the ways humans monitor and respond to their surroundings, engendering further cycles of change. This study will identify and quantify the ways in which these integrated cycles differ across cultures, biogeographic regions, and time. Quantitative and narrative analyses will identify the determinants of long-term dynamics, present-day patterns, and reservoirs of ecological and social resilience. Analytical approaches include structural-equation modeling, analysis of spatial and causal effects, and cross-site comparisons of case studies. As a practical test, project approaches and insights will be examined in the context of conservation planning at The Nature Conservancy.

Allelochemical Competition between Native and Exotic Phytolaccaceae Species in Korea

Date Presented: Friday Night

Lead Author: Yong kim
Co-Authors: Jon D. Johnson, Eun Ju Lee
Institutional Affiliations: Washington State University, Seoul National University
Primary Site: INT

Abstract: We analyzed the phenolic compounds and heavy metals in leaf extracts and compared morphology of three species of the Phytolaccaceae family found in Korea, including one native species (Phytolacca insularis) and two exotic species (Phytolacca esculenta and Phytolacca americana). To test allelochemical effects, we also examined seed germination and dry weight of seedlings of Lactuca indica and Sonchus oleraceus treated with the leaf extracts of the three Phytolacca species. The concentrations of total phenolic compounds were 3.9 mg/L in Phytolacca esculenta, 4.4 mg/L in Phytolacca insularis and 10.2 mg/L in Phytolacca americana. There was no significant difference in concentrations between P. esculenta and P. insularis, but the concentration of P. americana was two times higher than those of P. esculenta and P. insularis. Analysis of aqueous extracts from Phytolaccaceae by HPLC identified seven phenolic compounds (Gallic acid, Protocatechic acid, Chlorogenic acid, Caffeic acid, m-hydroxybenzoic acid, p-coumaric acid and Cinnamic acid). The total concentration of heavy metal on P. americana accumulated eight to sixteen times higher than those of P. esculenta and P. insularis respectively. The extract of P. americana showed the strongest inhibition on seed germination and dry weight of the two species. Their allelopathic effects were significantly different, despite the fact that P. esculenta and P. insularis had similar levels of total phenolic compound. We also found that P. americana had invaded Ullung Island, which suggested that P. americana had a high total phenolic compound and an excellent adaptation ability to the environment. Therefore, we concluded that the three species of Phytolaccaceae in Korea were distinguished by their significantly different allelopathic potentials and morphologies.

Allochthonous vs. Autochthonous Sources of Nutrients in a Coastal Lagoon - A Monitoring Program

Date Presented: Saturday Night

Lead Author: Amber Kozak
Co-Authors: Iris C. Anderson, Karen J. McGlathery
Institutional Affiliations: Virginia Institute of Marine Sciences, Virginia Institue of Marine Sciences, University of Virginia
Primary Site: VCR

Abstract: Hog Island Bay, a coastal lagoon on the Virginia Delmarva Peninsula and located within the Virginia Coast Reserve LTER site, receives nutrients from a variety of allochthonous and autochthonous sources. In an attempt to distinguish between these potential sources, a monitoring program was undertaken to identify nutrient concentrations and their spatial, seasonal, and interannual variability in the lagoon. Stations in triplicate were located along mainland creek, mid-lagoon, and back-barrier island sites. Samples were collected monthly and analyzed for DIN, DON, DOC, DIP and chlorophyll a. The monitoring study occurred during a period of drought, which steadily increased in severity from January 2001 until its peak in August 2002. The drought affected both physical and chemical parameters within the lagoon. Both water temperature and salinity values were lower in 2001 than 2002. The mainland creek salinities exceeded those of the barrier island sites during the summer of 2002, a reversal of the normal salinity gradient across the lagoon. During both 2001 and 2002, concentrations of all nutrients were generally highest along the mainland border, decreasing with distance across the lagoon for the majority of the year. Nitrate concentrations were highest in spring during 2001, paralleling base flow loadings observed by Stanhope et al. This same seasonal pattern was not observed for NO3- in 2002, most likely as a result of drought conditions. Concentrations of NH4+, DON and DIP in the lagoon tended to peak during summer, corresponding to higher water temperatures and to periods of high organic matter mineralization. Our results suggest that there is an allochthonous source of nitrate, likely groundwater transported from mainland watersheds. NH4+, DON, and DIP are more likely autochthonous in origin, derived from exudates of autotrophs within the lagoon or by recycling of organic matter, sources of which may include macroalgal or marsh detritus.

Alpine Ecology and Experiential Learning at the Niwot Ridge LTER

Date Presented: Saturday Night

Lead Author: Diane McKnight
Co-Authors: Jane Larson and Hector Galbraith
Institutional Affiliations: University of Colorado
Primary Site: NWT

Abstract: As part of NWTLTER Schoolyard LTER activities, for the past 6 years we have offered a summer field course for in-service and pre-service teachers. This 3-credit course provides extensive training in alpine ecology through both lecture and field trips. The course also covers topics in environmental and experiential education, such as the importance of helping students to develop "environmetnal empathy" for the natural habitats in their community. The teachers in the field class lead field trips of elementary and middle school students on field trips to the tundra laboratory on Niwot Ridge, and prepare educational materials to enhance these trips as final projects in the class.

Alterations of Ecosystem Structure: Dynamics of Jornada Basin Plant Communities

Date Presented: Friday Night

Lead Author: Laura F. Huenneke¹
Co-Authors: Michelle Buonopane² and Yang Xia²
Institutional Affiliations: Northern Arizona University¹ and New Mexico State University ²
Primary Site: JRN

Abstract: Long-term studies documenting temporal and spatial patterns in ecological communities, in combination with experimental manipulation, provide powerful insights into vegetation dynamics. Detailed descriptions of plant community structure (aboveground biomass and aboveground net primary production, or ANPP, by species) are provided from seasonal, spatially-explicit monitoring in 15 sites at the Jornada Basin LTER (three sites in each of five ecosystem types, including both grass- and shrub-dominated systems). Productivity patterns from year to year are generally explained by increases or decreases across the community, and the addition of ephemeral species in "good" years, rather than substitution of production by some species with production by others in different conditions. Site-to-site differences in composition contribute as much to overall regional plant diversity as do differences among ecosystem types. Experimental manipulations (removal of species or groups of species) have been used to explore the importance of biotic interactions and the ability of the community to respond to such perturbations. Neither dominant nor subordinate species respond strongly by increased growth or cover, at least over intervals of 5 years post-perturbation, and we have not observed new species (native or non-native) establishing in these experiments. We are pursuing seed bank studies to understand the relationship between community structure in the aboveground vegetation and the identity and abundance of propagules in the seed bank. Overall, both grass- and shrub-dominated Jornada Basin ecosystems demonstrate a severely limited capacity to recover biomass after perturbation.

An examination of food-web structure and complexity along two environmental gradients in the Florida Everglades

Date Presented: Friday Night

Lead Author: A. J. Williams
Co-Authors: J.C. Trexler
Institutional Affiliations: Florida International University
Primary Site: FCE

Abstract: Theory predicts that food-chain length may shorten along gradients of disturbance or lengthen along gradients of increasing productivity; however, in natural systems, these two environmental factors may vary simultaneously. We used stable isotopes to estimate food-chain length at 20 sites in the Florida Everglades representing a range of productivity and hydroperiod values. Food webs were characterized for all sites during both the wet and dry seasons. We measured TP content of soil, floc, and periphyton, as well as primary production of periphyton samples using light/dark bottle incubations as indicators of productivity. We analyzed 600 samples representing basal, intermediate, and top trophic levels for d15N and d13C. Amphipods and Seminole ramshorn snails were selected as primary baseline detritivore and herbivore taxa. Eastern mosquitofish and riverine grass shrimp represented intermediate trophic levels, and Florida gar were the top consumers at each site. Our results indicate more variation in trophic position and food-chain length can be explained as a function of joint productivity and hydroperiod descriptions than by single parameter gradients. We observed marked variation in trophic relationships among sites and between seasons. We also observed variation in d13C values of primary consumers among study sites, indicating spatial variation in the isotopic value of carbon consumed at the base of the food web. After correcting for spatial variation in isotopic signal, data revealed variation in d13C within and among regions. This indicates a possible shift in the relative roles of detrital and algal carbon among sites. We also calculated an index of detritivory to further examine the degree of detrital vs. algal carbon input in local food webs. A comparison of intermediate consumers across sites, corrected for variation in basal isotopic values, yielded little variation in d15N, but trophic position of eastern mosquitofish did vary among sites.

An experimental approach toward understanding soil organic matter dynamics

Date Presented: Friday Night

Lead Author: Elizabeth Sulzman
Co-Authors: Kate Lajtha², Richard Bowden³, Justin Brant¹, Bruce Caldwell⁴, Susan Crow², Heath Keirstead¹, Knute Nadelhoffer⁵, Janos Toth⁶, Kristin Vanderbilt⁷, Yuriko Y
Institutional Affiliations: ¹Dept. Crop and Soil Science, Oregon State University (OSU), Corvallis OR 97331; ²Dept. Botany, OSU, Corvallis OR 97331; ³Dept. Environmental Science, Allegheny College, Meadville, PA 16335; ⁴Dept. Forest Scienc
Primary Site: AND

Abstract: Changes in plant litter input quantity and quality are expected under most scenarios of global change, but resulting effects on soil organic matter (SOM) stability and turnover cannot yet be predicted. To address this gap, we established long-term manipulations to examine controls on SOM formation in a network of forests in the US and Hungary. Treatments include leaf additions, wood additions, leaf litter exclusion, root exclusion, and all detrital input exclusion. At all sites we are measuring dissolved organic matter in lysimeters, partitioning respiratory losses of C, analyzing light and heavy SOM chemistry, and conducting incubations to determine how litter manipulations affect the lability and chemistry of soil C and N pools. In addition, at most sites we are exploring microbial community composition (PLFA method), and at HJA we are using isotopes (13C, 14C, and 15N) to explore SOM stability. Results indicate increases in dissolved organic carbon (DOC) leaching in litter addition plots correspond with decreases in nitrate leaching. DOC fractionation has demonstrated significant differences in leachate chemistry from different detrital sources. Although total DOC decreases in all plots at depth, hydrophobic and hydrophilic acids show the greatest relative decrease, suggesting an active role in SOM formation. Using results of the above- and belowground detritus manipulations to partition sources of respiration, we estimated that aboveground litter decomposition accounts for 37, 30, and 25% of the total soil respiration at Harvard Forest, Bousson Experimental Forest, and H.J. Andrews, respectively; root and rhizosphere metabolism accounts for 33, 14, and 23% of the respective totals. The sum of our results indicates that alteration of SOM inputs can alter important soil C fluxes, that there is a rapid link between photosynthesis and belowground C allocation, and that the chemistry of detrital inputs is critical in long-term C stabilization and storage.

An experimental stream facility to evaluate ecosystem function of prairie streams

Date Presented: Saturday Night

Lead Author: Keith Gido
Co-Authors: Katie Bertrand
Institutional Affiliations: Kansas State University
Primary Site: KNZ

Abstract: Prairie streams are characterized by intense episodes of flooding and sever drought. Although these conditions are ideal for studying the effects of disturbance on stream ecosystems, the unpredictable nature of the hydrology makes field experiments challenging. Experimental streams provide an alternative that can be used to perform manipulative experiments which test the interactive effects of species composition and disturbance factors. We used an experimental stream facility at the Konza Prairie LTER site to evaluate the interactive effects of a prairie stream fish, Phoxinus erythrogaster, and simulated flooding. Ecosystem parameters measured in the experimental streams were compared to those in a natural stream to evaluate the limitations of using these experimental systems to mimic natural streams. At the scale of stream pools and riffles (1 to 10 m2), our experimental streams mimicked a wide range of ecosystem properties of natural streams including discharge, groundwater input, primary production, and macroinvertebrate assemblage structure. Moreover, we show that both natural and experimental systems respond similarly to manipulating the presence of a grazing minnow. Experimental streams were limited by the lack of invertebrate drift and reduced through flow relative to natural streams, but we have derived methods to compensate for these factors. The experimental stream facility at Konza Prairie is ideal for addressing ecosystem processes that occur at the scale of pools and riffles and will help address numerous questions regarding the dynamics of these harsh aquatic environments.

Analysis of High Elevation Ecosystems: The Niwot Ridge-Green Lakes Valley LTER Program

Date Presented: Saturday Night

Lead Author: Tim Seastedt
Co-Authors: W. D. Bowman, N. Caine. Diane McKnight, Alan Townsend, Mark Williams, Todd Ackerman, Patrick Bourgeron, Pam Diggle, Mark Losleben, Robert (Buck) Sanford, Steve Schmidt, Herm Sievering, Katharine Suding, and Carol Wessman
Institutional Affiliations: University of Colorado, University of Denver, University of California-Irvine
Primary Site: NWT

Abstract: Ecological studies of the climate and terrestrial and aquatic landscapes composing the Niwot Ridge - Green Lakes Valleys high-elevation region have been ongoing for over 50 years. Current changes in climate and atmospheric deposition of nitrogen to these systems have been identified, and these are causing rapid changes in some portions of this system but not in others. Interactions between climate and ecosystems with complex topographic gradients generate unique source and sink habitats for water and nutrients as a result of precipitation, energy, and chemical redistribution. High elevation lakes and the alpine tundra-forest ecotone are locations expected to receive the brunt of anthropogenic inputs obtained from the redistribution of exogenous materials from the regional environment, and from endogenous sources originating from other montane areas. Inorganic nitrogen inputs to lakes in the uppermost portions of Niwot Ridge experience inputs well in excess of N deposition from precipitation. At the alpine-forest interface, treeline functions as a particulate collector, resulting in the deposition of materials scoured from the alpine. A conceptual model is presented here that links terrestrial ecosystems to each other and to aquatic ecosystems. We report how atmospheric inputs as well as endogenous resources can be amplified or attenuated by transport processes. While transport processes determine local environmental forcings, biotic responses within and among sites mediate these effects. Ongoing research attempts to identify the extent to which biota, soils, and landscapes are changing due to environmental forcings, and the extent to which biotic processes can mediate change.

Andrews LTER

Date Presented: Friday Night

Lead Author: Mark Harmon
Co-Authors: Sherri Johnson, Julia Jones, Barbara Bond, Fred Swanson
Institutional Affiliations: PNW Research Station, Geosciences/OSU, Forest Science/OSU, PNW Research Station
Primary Site: AND

Abstract: The Andrews LTER program seeks to understand the long-term dynamics of forest and river ecosystems of the Pacific Northwest. The Central Question guiding this research is: How do land use, natural disturbances, and climate change affect three key sets of ecosystem services: carbon and nutrient dynamics, biodiversity, and hydrology? The principal spatial scale of inference for LTER studies is the Andrews Forest and adjacent area of 16,000 ha. The principal temporal extent spans the past 500 yr and to several centuries projected into the future. Essential long-term studies are being continued and others added to increase spatial and temporal overlap of scales. The 5 LTER core activities will be addressed by work in 7 component areas: (1) climate, (2) hydrology, (3) disturbance, (4) ecophysiology, (5) carbon and nutrient dynamics, (6) biodiversity, and (7) stream-forest interactions. These studies will examine the interaction of the drivers of change and responding processes and taxa, but the conceptual emphasis will be on temporal behavior, its causes, and its consequences for ecosystem change focusing on: (1) modulation, (2) temporal lags, (3) spatial coherence, (4) path dependence, (5) hysteresis, and (6) alternative stable states. A major goal will be to test predictive rules (i.e., hypotheses) regulating temporal behaviors. Another focus of synthesis will be small watersheds, an important landscape unit providing opportunity for integration of climatic, ecosystem, and hydrological processes as well as knowledge of temporal and spatial scaling. The ultimate goal in this integration is to create a spatially 3-dimensional (including subsurface and air flow) understanding of the temporal dynamics of the 3 states of matter involved in biogeochemical and hydrologic cycles within a watershed. Past experiments, long term records of climate, stream flow, nutrient exports, and vegetation change, as well as modeling will enhance this integration effort.

Anthropogenic Changes in the Sonoran Desert Landscape from Prehistory to the Present

Date Presented: Friday Night

Lead Author: Hoski Schaafsma
Co-Authors: Kris Gade, John M. Briggs
Institutional Affiliations: Arizona State University
Primary Site: CAP

Abstract: Farming by the prehistoric Hohokam Indians in the Sonoran Desert of Central Arizona had the capacity to significantly alter the soils, which has driven a change in the plant communities on these fields when compared to populations off the fields. This is most evident throughout a system of drainages in the northern Phoenix Basin. Cave Creek is the eastern most drainage of the northern basin and the location of this study. Hohokam farmers cultivated fields along this drainage for 400 years, from ca. A.D. 850-1250. This study uses pollen, seed bank and data on woody species along Cave Creek to understand the changes to the landscape that occurred in prehistory and the legacy that is still evident on the modern landscape. Plant communities were altered in composition, diversity, and richness. With these changes evident 750 years after the fields were abandoned, we look at the potential for change in future landscapes that is occurring in the modern Phoenix Basin.

Anthropogenic influences on biological uptake and transformations of nitrogen and phosphorus in southern California coastal streams

Date Presented: Saturday Night

Lead Author: Julie Simpson
Co-Authors: Al Leydecker
Institutional Affiliations: University of California, Santa Barbara
Primary Site: SBC

Abstract: The south coast of California has been subject to substantial development in recent decades, and the human population in this region continues to grow rapidly. Changes in both the intensity and the type of land use often result in increases in nutrient inputs (principally nitrogen and phosphorus) to nearby streams and rivers, and subsequent transport of these nutrients to the coastal ocean. Biological processing of nitrogen and phosphorus in stream water can alter both the form and the absolute amount of N and P which are delivered to coastal systems. We are conducting research to determine answers to the following questions: 1) How do changes in nutrient concentrations affect the composition of photosynthetic communities in streams and rivers, and 2) How do different components of the photosynthetic communities (algae, vascular plants, cyanobacteria) function with regard to nutrient processing, and how do those functions change across streams receiving a wide range of nutrient inputs? Through a combination of monitoring and experimental research, we ultimately hope to develop a predictive model for the community-level and functional responses of stream communities to land use changes on the south coast of California.

Anthropogenic Modifications Influence the Interactions Between the Geomorphology and Biogeochemistry of an Urban Desert Stream

Date Presented: Friday Night

Lead Author: W. John Roach
Co-Authors: R Arrowsmith, C Eisinger, NB Grimm, JB Heffernan, T Rychener
Institutional Affiliations: Arizona State University
Primary Site: CAP

Abstract: Greenways are increasingly common non-structural flood management systems that balance aesthetic and ecological features with flood protection. Unlike storm drains, structural (geomorphic) modifications in greenways may include retentive features like lakes, but the resulting floodplain system is often quite different than the preexisting one. We used historic aerial photography to document geomorphic changes resulting from the construction of a greenbelt along Indian Bend Wash, Scottsdale, AZ, in the early 1970’s. Catchment land use shifted from prehistoric agriculture (14th C) to desert and again to agricultural fields in the early 20th C. Beginning in 1955, suburban development has expanded from the mouth to headwaters of the wash, followed by greenway creation. This development has produced a shift in vegetation from desert scrub and mesquite bosques to a community dominated by low grasses and widely spaced trees. The geomorphic modifications of the floodplain interact with catchment-wide land use changes to alter sediment transport and deposition, spatial and temporal patterns of nitrogen storage, and vegetative community dynamics. Specifically, we hypothesize that urbanization has reduced sediment availability and retention structures have reduced maximum discharges; that new, artificial lakes are sinks for fine sediments and act as hot spots for nitrogen retention; and that changes in hydrology have dramatically altered nutrient availability.

Arctic LTER: Predicting the Future Ecological Characteristics of the Toolik Lake Region

Date Presented: Friday Night

Lead Author: John Hobbie
Co-Authors: Bruce Peterson, Gus Shaver, Linda Deegan, Anne Giblin, Ed Rastetter, Joe Vallino, John O'Brien, George Kling, Knute Nadelhoffer, Breck Bowden, Alex Huryn, Chris Luecke, Marc Stieglitz, Donald Walker
Institutional Affiliations: Marine Biological Laboratory,University of North Carolina at Greensboro, University of Michigan, University of Vermont, University of Alabama, Utah State University,Columbia University, University of Alaska - Fairbanks
Primary Site: ARC

Abstract: The site lies at 68oN in the northern foothills of the Brooks Range, Alaska, in tundra vegetation of sedges and grasses mixed with dwarf birch and low willows. The tundra, streams, and lakes at the site have been undisturbed and unchanged for more than 5,000 years; caribou and moose move freely over this region pursued by wolves and grizzly bears. Populations of lake trout, char, and Arctic grayling are in a pristine state, often dominated by very large and very old individuals. This allows the analysis of relationships in plants and animal communities in an ecosystem unaffected by an ecological legacy of human use. The climate of northern Alaska has changed remarkably over the past 30 years; the 0.7oC per decade increase in temperature could result in much more than the 3-5o total change predicted by GCM models for a doubling of CO2. Based on several types of observations, there appears to be a biotic response to this regional warming. For example, the NDVI (a satellite-based indicator of plant biomass) has increased in northern Alaska, and vegetation communities at Toolik Lake show a reduction in moss cover and an increase in shrubs. The goal of this LTER project is to predict the future ecological characteristics of the site based upon our knowledge of the controls of ecosystem structure and function as exerted by physical setting and geologic factors, climatic factors, biotic factors, and the changes in fluxes of water and materials from land to water.

Assessing semi-arid grassland recovery from livestock grazing

Date Presented: Saturday Night

Lead Author: Lydia Zeglin
Co-Authors: Deanna Pennington, Robert Parmenter, James Gosz, James Brunt
Institutional Affiliations: University of New Mexico
Primary Site: SEV

Abstract: The Sevilleta National Wildlife Refuge (Sevilleta NWR) in central New Mexico was established in 1974 when former ranchland was donated to the U.S. Fish and Wildlife Service. In 1989, the site became an NSF-funded Long Term Ecological Research (LTER) site. A recurring issue has been the extent to which the semi-arid grasslands of the Sevilleta NWR reflect the legacy of past livestock grazing. To address this question, grazing exclosure plots were constructed in 1992 on ranchland just north of the Sevilleta boundary. Three exclosure plots of 300 m by 300 m were established with analogs within the Sevilleta boundary. In addition, three continually grazed plots were located in the grazing land close to the exclosures. These nine plots were studied using satellite imagery and GIS analysis, and field measurements of soil properties and plant community composition. We measured greenness (as NDVI) at the nine plots for thirteen years beginning in 1989, three years before the establishment of the exclosures. The rate and extent to which NDVI values converge between the exclosures and the Sevilleta NWR plots serve as an estimate for grazing recovery time on the Sevilleta NWR. Present differences in soil properties and plant community structure on these plots illustrate complexities in the extent of grassland recovery. Analysis of both NDVI and grassland ecosystem properties proves a useful tool to address vegetation responses to grazing and to analyze rates of recovery following removal of domestic grazing animals.

Bacterial Enumeration in Florida Bay via Epifluorescent Microscopy

Date Presented: Friday Night

Lead Author: Matt Rogers
Co-Authors: Joseph N. Boyer, Susan K. Dailey
Institutional Affiliations: Southeast Environmental Research Center, Florida International University
Primary Site: FCE

Abstract: Bacterial Enumeration in Florida Bay via Epifluorescent Microscopy Abstract The Florida Everglades Restoration Project aims to reestablish the freshwater flow to Shark and especially Taylor Sloughs, which could impact Florida Bay’s delicate ecosystem. Although all aspects of the Bay may be affected, the microbial community structure of Florida Bay is of key importance. The reaction by the microbial community, especially heterotrophic bacteria, to the redirection of flow patterns through the everglades must be monitored in order to form hypotheses regarding the impacts to higher trophic organisms and the health and stability of the Bay. Since September 2001, we have utilized the nucleic acid stain DAPI and epifluorescent microscopy to enumerate the bacteria in Florida Bay. Large spatial and temporal differences were observed among different areas of the Bay. The highest cell counts came from the western Bay, and the lowest were shown to be in the eastern. The highest counts in each zone were typically associated with the fall (57% Sept-Nov), and to a lesser extent, the spring (25% Apr-May). Monthly low counts showed less seasonality, but the majority fell in the winter (36% Dec-Feb) and summer (29% June-Aug). These numbers are low compared to other estuaries but have been corroborated by flow cytometry.

Barre Woods Megaplot Soil Warming Experiment

Date Presented: Friday Night

Lead Author: J. M. Melillo¹
Co-Authors: P.A. Steudler¹, F.P. Bowles², J. Aber³, H. Lux¹, S. Morrisseau¹, E. Burrows¹, A. Chan¹
Institutional Affiliations: ¹Marine Biological Laboratory, ²Reseach Designs, Inc., ³University of New Hampshire
Primary Site: HFR

Abstract: Two of the major results of our original soil warming study were that: (1) warming stimulated the decay of a labile soil carbon pool; and (2) it also increased the availability of inorganic nitrogen to plants. Because of the small size of the original warming plots an important question we have not been able to answer conclusively is: · Has the increase in available nitrogen led to an increase in carbon storage in the vegetation? · And if yes, how much? In a systems context an additional question is: · What is the balance between the carbon lost from the soil and the carbon stored in the vegetation in response to soil warming? We are now addressing these important questions with a new warming experiment in the Barre Woods area of the Harvard Forest. During the summer and fall of 2001 we buried 5km of heating cable in a 30 x 30m plot. Cables were buried at a 10cm depth, spaced 20cm apart. A second 30 x 30m area was delineated to serve as the control plot. In April 2002, we began a one-year period of baseline measurements before turning on the heat in the new megaplot. These measurements included nitrogen mineralization, trace gas fluxes (CO₂, CH₄, N₂O), tree growth (dendrometer bands), an under story species survey, canopy foliage analysis (C:N, NIR), and lysimetry. Thermistors were installed in both plots to begin tracking soil temperatures. This year of baseline measurements provides us with an important set of pre-treatment data for the two plots. The power was turned on in May of this year, and the "manipulation phase" has begun. From the new megaplots, we expect to determine whether or not warming results in the movement of nitrogen from the soil to the trees and if there is movement, how this redistribution of nitrogen affects the net carbon balance of the ecosystem.

BASE FLOW AS A SOURCE OF NUTRIENTS SUPPORTING MACROALGAL BLOOMS IN A VIRGINIA COASTAL LAGOON

Date Presented: Saturday Night

Lead Author: Jennifer W. Stanhope
Co-Authors: Iris C. Anderson, James E. Perry, William G. Reay
Institutional Affiliations: Virginia Institute of Marine Science
Primary Site: VCR

Abstract: Base flow (ground water discharge to streams) may be an important source of nitrogen to coastal lagoons, leading to excessive nutrient loading and eutrophication. We hypothesized that: (1) streams in watersheds with higher percentages of forest cover have lower nitrogen concentrations and export rates; and (2) nitrogen in base flow, derived from agricultural sources, supports extensive mats of opportunistic macroalgae observed in shallow areas of the lagoons during some years. This study quantified base flow nutrient discharge rates from small watersheds with differing degrees of forest cover and determined relationships of nutrient concentrations to various watershed characteristics (i.e., land cover, soil drainage class). We measured monthly dissolved inorganic and organic nutrient concentrations and water discharge rates for one year from fourteen first-order streams along a north/south transect of the Virginia Eastern Shore. Monthly mean nitrate concentrations in northern streams (202.4uM) were significantly higher than in southern streams (114.8uM). Annual flow-weighted mean nitrate concentrations and export rates showed a significant inverse relationship to percent forest cover within southern stream watersheds (r2=0.53, p=0.029, N=9). In a multiple regression analysis with forest cover, we found that the addition of percent of developed land cover explained more of the variance of NO3- export rates (r2=0.86; p=0.003). The calculated TDN load from watersheds of Hog Island Bay (20,896 kg N/year), a shallow coastal lagoon on the Virginia Eastern Shore, was sufficient to support estimated mean macroalgal N demand (19,371 kg N/yr). Consequently, base flow derived from the shallow aquifer is likely a significant source of N supporting macroalgal production in Hog Island Bay. However, direct atmospheric deposition could quantitatively be more important than base flow as a source of N to Hog Island Bay.

Beetle-Fungal Complexes in Spruce Trees Across Sites in Alaska

Date Presented: Friday Night

Lead Author: Barbara Illman
Co-Authors: Kirsten Haberkern, Richard Werner, Kenneth Raffa
Institutional Affiliations: USDA Forest Service, Forest Products Laboratory, Madison, WI; University of Wisconsin, Madison, WI; USDA Forest Service (retired); University of Wisconsin, Madison, WI.
Primary Site: BNZ

Abstract: Landscape processes, such as succession, fire, gap formation, and nutrient cycling, are affected by eruptive bark beetle outbreaks. Although weather, host resistance, and natural enemies influence the population dynamics of these phloeophagous insects, the exact causes of region-wide population eruptions remain only partly understood. The spruce bark beetle, Dendroctonus rufipennis, has caused almost total mortality to several million hectares of pure spruce stands throughout Alaska and western Canada during recent years. A related species, Ips perturbatus, is the major cause of tree mortality in interior Alaska white spruce and Kenai Peninsula Lutz spruce. Bark beetles and their host trees are closely associated with a variety of microorganisms, especially sapstain fungi. Fungal species vary in pathogenicity to host trees, eliciting chemical responses in phloem tissue and potentially blocking xylem vessels. The beetle and fungal associations can range from mutually beneficial to antagonistic. Fungi may have an important role in the population dynamics of spruce bark beetles. We report here the major fungal species associated with D. rufipennis and I. perturbatus and beetle infested spruce trees. Beetles and host tissue (phloem and sapstain) were collected from 13 sites at Bonanza Creek and the Kenai Peninsula from 1999-2001. Beetles were collected from host trees and pheromone traps. Fungi were isolated from beetles by rolling the insects on selected culture media or by placing dilutions of water and crushed insects on selected media. The major fungi associated with D. rufipennis were Leptographium abietinum, Ophiostoma species A, and Pesotum species F. The major fungi associated with I. perturbatus were O. bicolor and L. abietinum. Preliminary evidence suggests differences in the composition of fungal associates of D. rufipennis with insect population phase.

Belowground meristem populations as regulators of grassland dynamics: A cross-site study

Date Presented: Saturday Night

Lead Author: Harmony J. Dalgleish
Co-Authors: David C. Hartnett, Gail W. T. Wilson, Emily J. Benson
Institutional Affiliations: Kansas State University
Primary Site: KNZ

Abstract: Studies of plant populations are critical for linking organismic to ecosystem-level phenomena and for understanding mechanisms driving responses to global change and patterns of biodiversity. In perennial grasslands and other herbaceous communities, the belowground population of meristems (the bud bank) plays a fundamental and primary role in local plant population recruitment, persistence and dynamics, and may also play a key role in patterns of plant community diversity, stability, and invasibility. At the ecosystem level, bud banks and meristem limitation can strongly influence patterns of primary productivity and ecosystem responses to environmental change. Our research compares bud bank populations and meristem limitation across six Great Plains sites that vary 3-fold in precipitation and 4.5-fold in productivity. Preliminary data support our hypothesis that bud bank densities vary across regional gradients. Meristem densities are the highest in tallgrass prairie, intermediate in mixed-grass prairie and lowest in short grass steppe. Using long-term data collected at each site, we shall test the hypotheses that meristem limitation constrains temporal variability in productivity in arid to semi-arid grasslands and that meristem density thresholds regulate the invasibility and stability of grassland plant communities. We are examining the effects and ecological consequences of fire, grazing and water limitation on bud bank populations using replicated long-term treatments at Konza Prairie LTER. Comparison of annually burned and infrequently burned prairie show a two times greater density of rhizome buds in burned areas (1830 buds/m^2 burned vs. 733 buds/m^2 unburned). Significantly higher tiller:bud ratios on annually burned prairie (1.3:1) than on infrequently burned prairie (0.7:1) suggests that fire suppression may reduce productivity by increasing belowground meristem limitation in these grasslands.

Biogeochemical impacts of major reservoirs on the Kalamazoo River system

Date Presented: Saturday Night

Lead Author: Nicole Reid
Co-Authors: Steve Hamilton
Institutional Affiliations: Michigan State University
Primary Site: KBS

Abstract: Impoundments change the characteristics of a water body from a river to a lake, affecting chemical, physical and biological characteristics. Two reservoirs of differing trophic status were sampled weekly in order to quantify the roles of the reservoirs as sinks for nutrients. Lake Allegan is a 1587-acre hypereutrophic impoundment, and is located 43 miles downstream of Morrow Lake, a 1000- acre eutrophic impoundment on the same river. No major tributary inputs exist between the reservoirs. Despite their spatial proximity, in 1999 a Total Maximum Daily Load (TMDL) for phosphorus was developed for Lake Allegan to control summer algal blooms, whereas Morrow Pond lacks summer algal blooms. The inflow and outflow waters of Lake Allegan and Morrow Pond were sampled and analyzed for inorganic nitrogen forms, phosphorus, major solutes and chlorophyll. The biogeochemical changes in river water during passage through the reservoirs will be analyzed, and the two systems will be compared.

Biogeochemical processes stabilizing soil aggregates from agricultural ecosystems

Date Presented: Saturday Night

Lead Author: Eun-Jin Park
Co-Authors: Heather.A. Dopp, Alvin.J.M. Smucker
Institutional Affiliations: Michigan State University
Primary Site: KBS

Abstract: Stable soil aggregates preserve intra-aggregate porosities that do not collapse during wetting and drying cycles. Stable micropore networks increase the retention of carbon which feeds back into the formation of more stable aggregates. We investigated aggregate stability by wet sieving and by polar tensile strength crushing resistances of aggregates from agricultural ecosystems in two Hoytville and Wooster soil series. Carbon contents, textural distributions, and intra-aggregate porosities were compared. Soil carbon contents in aggregates from no tillage (NT) systems were 1.6 and 2.2 fold greater than conventional tillage (CT) systems from Hoytville and Wooster, respectively. Water stability of soil aggregates increased with increasing C content and became most stable as C contents exceeded 4%. C content and water stability of aggregates showed positive correlations with intra-aggregate porosities that decreased by 6-7% in CT aggregates. Polar tensile strength of dry aggregates increased with increasing bulk density, C, and clay content. These results suggest that non-disrupted and higher intra-aggregate porosities retained more internal carbon. This is indirect evidence of accelerated organo-clay mineral interactions.

Biogeochemistry and Soil Organic Matter Accumulation in a Salt Marsh

Date Presented: Saturday Night

Lead Author: Cassondra Thomas
Co-Authors: Linda Blum
Institutional Affiliations: University of Virginia
Primary Site: VCR

Abstract: On the eastern shore of Virginia, marshes keep pace with sea level rise by sediment organic matter (SOM) accumulation. While many factors affect the rate of SOM accumulation, this work examines the effect of soil texture, crab burrows, and iron on plant production at Lower and Upper Phillips Creek (LPC and UPC, respectively) marshes. LPC sediments are coarser, low in SOM, and support fiddler crabs. UPC sediments are heavier, higher in SOM, and lack fiddler crabs. Two experimental manipulations were done at each location; Fe addition (5.49 g FeCl2/m2) and either crab removal (LPC) or artificial burrow construction (UPC). Sulfate reduction rate (SRR) constants, above ground biomass, root production, and delta S34 values for Spartina alterniflora leaves were consistent with the hypothesis that production is limited by sulfide from sulfate reduction in LPC but not in UPC. Fe addition increased sulfide at both locations yet had different effects on SRR constants and delta S34 values, implying that SOM accumulation is controlled indirectly by sulfate reducing bacteria through their effect on plant production and not through decomposition directly. Delta S34 values may be a potential indicator of marsh susceptibility to state change as a consequence of sea-level rise.

Biogeochemistry in the hyporheic zone of an alpine stream.

Date Presented: Saturday Night

Lead Author: Matthew Miller
Co-Authors: Diane McKnight
Institutional Affiliations: University of Colorado-Boulder, INSTAAR
Primary Site: NWT

Abstract: Humic substances are a class of refractory organic biomolecules that are present in most natural waters. These substances are important components of natural waters in that they can form complexes with toxic metals, regulate the color of natural water and therefore the depth to which light can penetrate, buffer pH, provide an energy source for microbes, and as is recently being discovered, act as electron acceptros in reducing conditions. Our objective in this study is to gain insight into the role of humic acids as electron acceptors in the hyporheic zone of an alpine stream. Data was collected over a four week period from the hyporheic zone of a stream in the Green Lakes Valley, a headwater catchment that is part of the Niwot Ridge LTER program. Using fluorescence spectroscopy, we have characterized the oxidation state of quinone moieties in humic substances found at this site. A tracer experiment was conducted using lithium bromide to gain a better understanding of the flow paths into and out of the hyporheic zone. Preliminary data from the tracer experiment and hyporheic sampling is presented here. Tracer data in conjunction with dissolved organic carbon (DOC), conductivity, fluorescence index, iron speciation, and fluorescence spectroscopy has provided a good framework to examine the role of humic acids as electron acceptors.

Biogeochemistry of Soils: Effects of Soil Freezing on Soil Solution Chemistry at Hubbard Brook Experimental Forest

Date Presented: Friday Night

Lead Author: Samuel Fashu-Kanu
Co-Authors: Charles T. Driscoll
Institutional Affiliations: Syracuse university
Primary Site: HBR

Abstract: Global climate change could significantly impact biogeochemical cycles in northern ecosystems, by causing reduction in snow cover and consequently, soil temperature. The reduction in depth and duration of snow pack may cause the soil to freeze extensively and increase the freeze thaw cycle. Conceptually, soil freezing may cause mortality of fine roots and microorganisms, root impairment, fragmentation of litter and degradation of soil litter releasing labile organic matter to the soil. This could accelerate nitrification and mineralization, with resultant increase in nitrate (NO3-) leached into the soil water. Leached NO3- could enhance the depletion of nutrient base cations from available soil pools and influence the acid-base chemistry of soils and surface waters. In this experiment, soil solution nitrogen was collected from the humus layers (Oa horizons) of randomly designated adjacent paired treatment and reference subplots, each 10 m X 10 m, from each of four sites; East Mt. Kineo, West Mt. Kineo, lower valley and upper valley plots at Hubbard Brook Experimental Forest in the white mountains of New Hampshire. These sites were selected to maximize spatial variability. Nitrate concentrations (NO3-) from the treatment and reference plots were compared before and after the treatment process. The treatment plots were allowed to accumulate snow at the normal rate with the reference plots from May 2001-December 2002, after which the treatment plots were kept snow free from January 2003. The results indicated that disturbances associated with installation of the lysimeters dissipated towards the end of the pretreatment period. The concentrations during the winter, snowmelt and summer period showed significant seasonal variation in all plots and there was no significant difference in the NO3- concentration between the treatment and reference plots at the end of the pretreatment period.

Biogeochemistry of Soils: Effects of Soil Freezing on Soil Solution Chemistry at Hubbard Brook Experimental Forest

Date Presented: Friday Night

Lead Author: Samuel Fashu-Kanu
Co-Authors: C. T. Driscoll, P. M.Groffman, T. J Fahey, J. P. Hardy
Institutional Affiliations: Syracuse University, Institute of Ecosystem Studies, Cornell University, ERDC-CRREL
Primary Site: HBR

Black grama seedling herbivory and mortality in the Chihuahuan desert: An experiment across shrub-grass ecotones

Date Presented: Friday Night

Lead Author: Nellie I. Khalil
Co-Authors: Brandon T. Bestelmeyer, Debra P. C. Peters
Institutional Affiliations: USDA-ARS Jornada Experimental Range
Primary Site: JRN

Abstract: Limitations to grass seedling recruitment, including herbivory and abiotic causes of seedling mortality, are expected to differ across a desert grassland shrub-grass ecotone. Grass seedlings in shrub-dominated ends of ecotones will likely have higher rates of mortality due to herbivory (because of increased predator presence and increased seedling visibility) and overall mortality (due to harsher abiotic conditions). We tested this hypothesis by placing 3-week-old black grama seedlings across three replicate ecotones (each containing a shrub-dominated position, a midpoint, and grass-dominated position) at the Jornada Basin LTER site, and observed rates of herbivory and overall mortality. Rodent, lagomorph, and grasshopper abundances were measured across the three ecotone positions. Rates of mortality due to herbivory and overall mortality were found to be the highest in the shrub-dominated position, followed by the midpoint position, and was least in the grass-dominated position. Small animal abundance did not follow this pattern: rodents and lagomorph pellets were most prevalent in the midpoint position, while grasshoppers were most prevalent in the grass-dominated position. Field observations indicated that the shrub-dominated position had the highest rate of overall mortality due to environmental harshness (e.g. high soil temperature). Increased visibility of grass seedlings to predators in the shrub-dominated position, rather than differences in predator abundance, may have resulted in increased herbivory rates in the shrub-dominated position.

Bonanza Creek LTER

Date Presented: Friday Night

Lead Author: F. Stuart Chapin

Abstract: The Bonanza Creek LTER focuses on understanding long-term consequences of changing climate and disturbance regimes in Alaskan boreal forest. The research is organized into three themes: (1) forest dynamics, addressing changes in populations and communities following disturbance, (2) the carbon cycle, which changes during succession and also influences nutrient availability and microenvironment, and (3) regional and landscape controls over disturbance regime, focusing on processes responsible for the timing, extent, and severity of disturbance. Our research design uses experiments and observations in intensive sites in floodplains, south-aspect uplands, and north-aspect uplands to document the processes that drive successional change. We establish regional context for intensive studies by analysis of processes and patterns in two large regions: the relatively uniform Alaskan interior, and a climate gradient from the warmest to coldest areas in Alaska. Synthesis addresses three important ecological issues: (1) how species characteristics and diversity influence biogeochemistry and disturbance regime, (2) how processes and patterns scale in space and time, and (3) how positive and negative feedbacks influence the sensitivity of ecosystems to perturbations such as changes in climate and disturbance regime.

Bosque Ecosystem Monitoring Program/Sevilleta Schoolyard: Combining Long-Term Monitoring with Community Outreach

Date Presented: Saturday Night

Lead Author: Kim Eichhorst
Co-Authors: Mary Dwyer, Dan Shaw, Mary Stuever, Cliff Crawford
Institutional Affiliations: Bosque School, Bosque School, Seldom Seen Expeditions, University of New Mexico
Primary Site: SEV

Abstract: The Bosque Ecosystem Monitoring Program (BEMP) is long-term ecological research utilizing K-12 teachers and students to monitor key indicators of structural and functional change in the Middle Rio Grande riparian forest (bosque) over time. Involving approximately 400 students per year in data collection and lab processing helps to increase their understanding and appreciation of science and this system. At the same time, abiotic (e.g., groundwater level, precipitation) and biotic (e.g., plant productivity, vegetation cover) data gives us insight into the biological quality and connectivity of various sites. The current 16 sites span 280 km, and are located on public, private, pueblo, and federal lands. Some sites are used to host guest schools that are interested in being a part of BEMP and do not yet have their own site or time to monitor a site year-round. Every fall, BEMP hosts a teacher workshop for teachers currently involved or wanting to be involved in BEMP. The workshop focuses on training teachers to collect various types of data, lab processes, computer work, and using the data to teach science and math in their classrooms. At the end of the year, BEMP hosts a Spring Student Congress for all classes and schools involved at various sites that year. Students present to each other what they’ve learned at their sites along with any special projects done in the bosque. BEMP offers a Bosque Internship course at the University of New Mexico. Undergraduates and graduates study the bosque, environmental education, and how to work with K-12 students. Site representatives, UNM interns, and scientists provide quality control on the data. BEMP data have been requested by the U.S. Corps of Engineers, the U.S. Geological Survey, the Middle Rio Grande Conservancy District, and the City of Albuquerque Open Space Division. Dynamics between plant species diversity, primary production, groundwater, river flow, and precipitation are shown to be complex, varying between sites.

Building a GIS of the Kellogg Biological Station LTER Site

Date Presented: Saturday Night

Lead Author: Suzanne Sippel
Co-Authors: Phil Robertson
Institutional Affiliations: Michigan State University
Primary Site: KBS

Abstract: We are preparing a GIS for the KBS LTER site. The GIS will contain georeferenced background data such as aerial photographs, DEM, experimental treatment boundaries, soils, vegetation and field instrumentation locations. This will provide convenient templates on which to record critical information of past and future manipulations, sampling points, and spatial data such as our crop yield maps and spatial variability samplings. The GIS will be linked to the LTER relational database management system so that spatial data can be displayed for mapping. A GIS of the Kalamazoo River Watershed will also be prepared in order to facilitate extrapolation of our LTER findings to the Southwest Michigan landscape. This will contain a TM scene, aerial photography, recent and presettlement land cover, DEM, roads, wetlands, lakes, streams and soils.

Calcium and phosphorus uptake by plants in secondary succession at Luquillo Experimental Forest, Puerto Rico, USA.

Date Presented: Friday Night

Lead Author: Bruce Haines
Co-Authors: Bruce Haines and Robert Potter
Institutional Affiliations: The University of Georgia, Athens, GA
Primary Site: CWT

Abstract: Disturbances to forests such as landslides, hurricanes and clear-cutting redistribute resources including light, nutrients and water in space and time. Species are expected to differ in their resource requirements and to occupy different regions along resource gradients. Nutrient uptake was evaluated for 14 species using the Michaelis-Menton model.The parameters of Vmax and Km were estimated for Ca and P uptake using radioactive tracers with detached root. Phytolacca rivinoides, an annual pioneer species, had Vmax and Km values for Ca of 5.9 mg Ca /g dw/30 min and 33 mg Ca /l respectively and for P of 0.06 mg P / g dw/30 min and 0.24 mg P / l. Cecropia schreberiana, a pioneer tree, had Vmax and Km values for Ca of 1.6 and 11 respectively. In contrast, Manilkara bidentata, a canopy tree, had Vmax and Km values for Ca of 0.95 and 61 and for P of 0.0025 and 0.35 respectively. Among plant species the Vmax ratios of Ca:P ranged from 20 to 400 while the Km ratios for Ca: P ranged from about 10 to 200. Future work needs to focus on discovery of ecological correlates between nutrient uptake kinetic parameters, light curves, and resource gradients in the field.

Calcium supply in northern hardwood forests depends on weathering of apatite

Date Presented: Friday Night

Lead Author: Ruth Yanai
Co-Authors: Joel D. Blum, Carmen Nezat, Steven P. Hamburg, Mary A. Arthur, Thomas G. Siccama
Institutional Affiliations: SUNY-ESF, University of Michigan, Brown University, University of Kentucky, Yale University
Primary Site: HBR

Abstract: Acid rain and repeated forest harvest are thought to threaten the supply of calcium to forested ecosystems. Ecosystem budgets for New Hampshire northern hardwoods show that young stands (<30 y old) mobilize Ca at rapid rates (3.3 to 4.7 g Ca m-2 y-1), based on the rates of Ca export in streamwater and accumulation in vegetation and the forest floor. In contrast, older stands are in approximate steady state (losing 1 g Ca m-2 y-1). If young stands tap a pool of soil Ca unavailable to older stands, then repeated harvest will not result in rapid Ca depletion, as has been predicted based on rates of export and weathering in older stands. If, on the other hand, rapid Ca uptake by young stands hastens the depletion of readily available pools, sustainable forestry may be threatened. We have identified apatite (Ca phosphate) at depth in soils at the Hubbard Brook Experimental Forest (65 g Ca/m2 in E and B horizons and 6 g Ca/m2 per cm of depth in the C horizon), based on sequential extractions and P:Ca and Ca:Sr ratios. We propose that apatite weathering is accelerated in young stands, perhaps because P is more limiting than N shortly after forest disturbance. We analyzed soils and plant material from 10 additional sites in New York, Pennsylvania, and Maine. The apatite source shown to be important at Hubbard Brook is important in all sites on glaciated granitic terrain, but not in the sedimentary Allegheny Plateau.

Canopy Microclimate Effects of Three Desert Shrub Species

Date Presented: Saturday Night

Lead Author: Gregory Bonito1
Co-Authors: Scott Collins1, Doug Moore1, John Vande Castle1, William K. Michener 1, Kevin Delin 2
Institutional Affiliations: University of New Mexico, Albuquerque 1; NASA Jet Propulsion Laboratory, Pasadena
Primary Site: NET

Abstract: Advances in science often result from the use of new technologies and instrumentation. For example, the invention of the microscope opened the window to the science of microbiology, and landscape ecology became possible after the advent of remote aircraft and satellite ‘macroscopic’ technologies. The integration of current ‘off the shelf’ technologies including microcomputers, microsensors, microelectronics, wireless communications, and the Internet allow for a new class of instrumentation, offering novel design and application possibilities, and that can scale across space and time to create scalable environmental sensor networks. In this study we employ the use of one these new ‘macroscopic’ instruments, called a Sensor Web, to measure the microclimate canopy effect of three desert shrub species (Juniperus monosperma – Juniper, Larrea tridentata - Creosote, and Prosopic glandulose var. tirreyana - Mesquite). This poster will highlight our current scientific findings and our experience using this new technology.

Canopy Nitrogen Uptake at a Colorado Subalpine Spruce-Fir-Pine Forest

Date Presented: Saturday Night

Lead Author: Timothy Tomaszewski^1,2
Co-Authors: Richard L. Boyce², Herman Sievering^1,2
Institutional Affiliations: Department of Environmental Science, University of Colorado at Denver¹, Institute of Arctic and Alpine Research²
Primary Site: NWT

Abstract: A study at a Colorado spruce-fir-pine forest was undertaken to obtain canopy nitrogen uptake (CNU), N reallocation, and foliar N requirement. Wet deposition, dry deposition, and throughfall fluxes of ammonium and nitrate were measured during the 2000, 2001 and 2002 growing seasons. Determination of CNU, for both ammonium and nitrate, was obtained by subtracting throughfall (TF) flux from the sum of wet deposition (WD) and dry deposition (DD): CNU = WD+DD-TF. Canopy N uptake efficiency (CNU/[WD+DD]) for ammonium (0.9) was consistent across the 3 seasons. For nitrate, this efficiency was 0.8 (2000), 0.7 (2001) and 0.6 (2002). Foliar N requirement for growth was about 19 (2000), 22 (2001) and 12 (2002) kg N ha^-1 yr^-1. Growing season estimates of CNU were approximately 2 (2000) and 3 (2001 and 2002) kg N ha^-1. Thus, CNU may contribute 10-25% of the foliar N requirement for canopy growth. Mountain upslope winds bring substantial amounts of anthropogenic N to this forest during the growing season, thereby contributing to CNU. Given that a sizable fraction of CNU is anthropogenic in origin, the forest’s N cycle has likely undergone substantial changes on a decadal time scale.

Carbon cycling at the Harvard Forest: bottom-up and top-down approaches.

Date Presented: Friday Night

Lead Author: Lucy Hutyra
Co-Authors: Barford, C.C., Bryant, D.M., Chow, V.Y., Jones, C.M., Munger, J.W., Pyle, E.H., Urbanski, S.P., Wofsy, S.C.
Institutional Affiliations: Harvard University
Primary Site: HFR

Abstract: Agricultural land use and active management have changed the vegetation dynamics of the New England landscape. In working to understand the linkage between the forest and atmosphere, our study uses both bottom-up and top-down approaches to quantify carbon pools and fluxes. Carbon dioxide eddy flux measurements at Harvard Forest have revealed annual carbon sequestration ranging from 0.8 to 4.2 MgC ha-1 (mean ~ 2.2 MgC ha-1 yr-1) from 1991 to 2002. The observed inter-annual variations reflect short-term (hourly to monthly) response of the ecosystem to environmental forcing (temperature, sunlight, soil moisture) as well as delayed impact of climatic variation on factors such as decay of prior year litter, or mortality or morbidity due to drought stress. The forest’s mortality and recruitment demographics characterize the future composition of the live biomass and create the material for decomposition. Litter fall mass and chemistry provide a metric for assessing inter-annual variation in photosynthetic capacity and nutrient cycling. The role of these processes in controlling carbon exchange at Harvard Forest has been explored through a series of complementary modeling studies.

Carbon exchange along a soil moisture gradient after fire.

Date Presented: Friday Night

Lead Author: Isla H. Myers-Smith
Co-Authors: A. D. McGuire, J. W. Harden and F. S. Chapin
Institutional Affiliations: University of Alaska Fairbanks
Primary Site: BNZ

Abstract: The Alaskan interior contains large carbon reserves stored in poorly drained ecosystems. With warming, these areas of the boreal forest may experience more frequent or extensive stand replacing fires, and thus change the primary factors controlling carbon emissions. This study will quantify the ground level emissions of the greenhouse gasses CO₂ and CH₄ along a soil moisture gradient on the Tanana River Floodplain that burned in 2001. The relationships between CO₂ and CH₄ release and the controlling factors of soil moisture, water table level, temperature, and soil carbon will be determined by automated and manual field data. The fire regime and hydrologic history of the site will be determined from the analysis of soil cores. These multiple data sources will be used to analyze and model the changes in carbon since the occurrence of the fire disturbance. Vegetation changes are occurring very rapidly at this site. The initial expansion of the bog area in the summer of 2002 suggests that permafrost degradation occurred. However, in the summer of 2003, the bog area dried and grasses and sedges have grown over the sphagnum mat. This has increased transpiration and decreased the water levels further. The soil core data reveal a pattern of contraction and expansion of the bog after fire suggesting that permafrost and vegetation dynamics are major controllers of the site hydrology. We report one year of preliminary data on changes in soil moisture, vegetation, active layer and gas fluxes in response to intra-seasonal climate variation along the soil moisture gradient. The site history constructed from aerial photographs, vegetation surveys and soil core profiles and the relationships between hydrology, climate, vegetation and carbon exchange will be used to improve projections of carbon exchange under climate change scenarios for this boreal floodplain ecosystem.

CARBON EXCHANGE BETWEEN AN EVERGLADES RIVERINE MANGROVE WETLAND AND ADJACENT TIDAL CREEK

Date Presented: Friday Night

Lead Author: Melissa Romigh (1)
Co-Authors: S.E. Davis (1)
Institutional Affiliations: Texas A&M University (1)
Primary Site: FCE

Abstract: Coastal outwelling of dissolved organic carbon (DOC) and particulate organic carbon (POC) and nutrients from mangrove wetlands can have a significant effect on coastal trophic food webs and influence the biogeochemistry of marine environments. The extent to which organic carbon and other nutrients from mangrove production are exported into the surrounding coastal environment or are retained within the mangrove system is still debated. The objective of this study is to determine both tidal and intra-annual variability in fluxes of carbon in the riverine mangrove forest zone along Shark River in the Florida Coastal Everglades (FCE). We employ a flow-through flume sampling technique that has been successfully used to quantify fluxes of materials in other mangrove and salt marsh ecosystems. By calculating changes in concentrations of flume and tidal creek water, we quantify net area fluxes of carbon (POC, DOC and DIC) for both short term and seasonal changes in freshwater inflow. Such data are necessary to understand the short-term importance of water source (Everglades vs. Gulf of Mexico) and nutrient inputs and long-term importance of sea-level rise on mangrove ecosystem structure and function along Shark River and ultimately for the entire FCE. Previous studies in the Everglades have measured the highest levels of POC and DOC concentrations during wet seasons and variable amounts during dry seasons. Salinity, temperature, pH, conductivity, and dissolved oxygen (DO) of tidal creek water were monitored continuously during sampling. Notable changes occurred in DO, pH, conductivity, and salinity of tidal creek water, all of which increased during flood tide and decreased during ebb tide. Preliminary data on TSS, chlorophyll a and particulate organic matter content of tidal creek and flume water samples indicate slightly more organic matter is exported to adjacent tidal creek water during ebb tide than imported to the mangrove soil surface with flood tide.

Carbon resources, soil organisms, and nitrogen availability: landscape patterns in a north temperate forest

Date Presented: Friday Night

Lead Author: Melany Fisk ¹
Co-Authors: Timothy Fahey ², Peter Groffman ³
Institutional Affiliations: ¹ Appalachian State University, ²Cornell University, ³Institute of Ecosystem Studies
Primary Site: HBR

Abstract: The interactions among different components of detrital foodwebs are essential to our understanding of biotic processing of C and of the linkages between C and nutrient cycling. Our objective was to identify potentially important interactions in detrital foodwebs at the Hubbard Brook Experimental Forest, NH, by exploring relationships among detrital C sources, microbial biomass, microarthropod abundance, and nitrogen (N) availability as they vary across the landscape. We observed significant spatial variation in microarthropod abundance (106,000/m2 to 184,500/m2, averaged over 4 years) across low-, mid- and high-elevation hardwood sites and spruce-fir sites. The same pattern was observed for microbial biomass in the Oe horizon, but not for net N mineralization in the Oe horizon or for microbial biomass or net N mineralization in the Oa horizon. A significant positive correlation between microarthropod abundance and microbial biomass suggests that these groups respond to similar factors across the landscape. They were not related to forest floor mass or to annual aboveground fine litterfall flux, but were positively correlated with fine root biomass, suggesting that C supply from roots plays a key role in the detrital foodweb of these forests. Patterns of microarthropod abundance were not related to net N mineralization and our results do not suggest any link between spatial variation in detrital foodwebs and N recycling.

Changes in Agrarian, Human and Natural Systems of the Flint Hills of Kansas

Date Presented: Saturday Night

Lead Author: Leonard Bloomquist
Co-Authors: Gerad Middendorf, and Derrick Cline
Institutional Affiliations: Kansas State University
Primary Site: KNZ

Abstract: The Konza Prairie LTER site includes more than 3400 ha of native tallgrass prairie in the Flint Hills of northeastern Kansas. The Flint Hills region covers approximately 50,000 km2 of eastern Kansas and Oklahoma, and encompasses the largest remaining tract of unplowed tallgrass prairie in North America. Grazing by native ungulates (primarily Bos bison) was historically an important process in these grasslands, until the near extirpation of bison and their replacement with domestic cattle. The Flint Hills emerged as a major cattle production region in the late nineteenth century, with cattle grazing on its blue stem grasses before they were shipped to meat packing plants. Cattle ranching remains an important part of the agrarian landscape in the region, but the role of the Flint Hills in the beef commodity chain changed substantially during the twentieth century. A related change is the decline in the human population in much of the region. On the other hand, some counties have experienced population growth through urban sprawl emanating from nearby cities. Here we present evidence of changes in the agrarian and human systems of the Flint Hills region, plus show how the native grassland ecosystems of the region have been affected by these changes.

Changes in Nutrient Content, C and N Stable Isotope Ratios, and Molecular Composition During Decomposition of Seagrasses and Mangrove Leaves in Florida Bay

Date Presented: Friday Night

Lead Author: Josh Cloutier
Co-Authors: Jim Fourqurean, Jill Schrlau, Nagamitsu Maie, Rudolf Jaffe and Toshikazu Miyoshi
Institutional Affiliations: Florida International University
Primary Site: FCE

Abstract: The decomposition of the mangrove Rhizophora mangle and the seagrass Thalassia testudinum was examined using litterbags along a natural gradient in nutrient availability. Seagrass leaves had a higher fraction of their biomass in the labile pool (57%), compared to mangrove leaves (36%) and seagrass rhizomes (29%); the overall decomposition rates of the starting material reflected the fractionation into labile and refractory components. There was no relationship between the N or P content of the starting material and the decomposition rate. Nutrient availability had no influence over decomposition rate, and mass was lost at the same rate from litterbags that were buried in the sediment and litterbags that were left on the sediment surface. The dynamics of N and P content during decomposition varied as a function of starting material and burial state. N content of decomposing mangrove leaves increased, but seagrass rhizomes decreased in N content during decomposition while there was no change in seagrass leaf N content. These same general patterns held for P content, but buried seagrass leaves increased in P content while surficial leaves decreased. d13C and d15N changed by as much as 2 ppt during decomposition. Changes in the chemical composition of these litterbag samples were also investigated through GC/MS lipid biomarker analysis and CP-MAS 13C Nuclear Magnetic Resonance, while changes in the lignin-phenol content were examined by TMAH Thermochemolysis.

Changes in Soil Carbon, Aggregation and Trace Gas Fluxes Immediately Following Cultivation of an Undisturbed Soil Profile

Date Presented: Saturday Night

Lead Author: A. Stuart Grandy
Co-Authors: G.P. Robertson
Institutional Affiliations: W.K. Kellogg Biological Station, Michigan State University
Primary Site: KBS

Abstract: Cultivation of previously undisturbed soils commonly results in the loss of 40-60% of initial C and N from surface horizons. In the tropics losses typically occur within months of cultivation, but a lack of data for temperate ecosystems prevents similar generalizations on a time scale less than about five years. We investigated changes in soil C pools, aggregation, nitrous oxide fluxes and denitrification in the first sixty days following cultivation of a previously untilled mid-successional community in southwest Michigan. Additionally, we designed a litter removal experiment to determine whether immediate, measurable changes were due to acceleration of soil organic matter dynamics or the incorporation of above-ground plant biomass and litter. Cultivation had an immediate impact on all measured properties: within two weeks we found differences in dissolved organic carbon, inorganic N, trace gas fluxes, and field-moist aggregates. A decline in water-stable aggregates coupled with a shift in the distribution of inter- and intra-aggregate light fraction organic matter likely contributed to changes in carbon dioxide fluxes. Increased nitrous oxide fluxes following cultivation were closely related to increases in N availability. Cultivation also reduced denitrification enzymes, probably due to rapid aggregate turnover which reduced the frequency and persistence of anaerobic microsites. Sites where above-ground plant biomass and litter were removed prior to cultivation had trace gas fluxes that were higher than in control sites but lower than in plots where above-ground resources were incorporated with cultivation. The rapid changes in nutrient mobilization observed here have implications for understanding the historical impact of agricultural expansion and for mitigating that impact via soil C sequestration and other means.

Changes in Soil Organic Carbon Cycling as Juniper Forests Invade Tallgrass Prairie: A delta 13C Stable Isotope Approach

Date Presented: Saturday Night

Lead Author: Dixie Smith
Co-Authors: Roxane Fagan, Loretta Johnson
Institutional Affiliations: Pittsburg State University, Kansas State University
Primary Site: KNZ

Abstract: Woody plant expansion into grasslands has been occurring across the Great Plains. The purpose of this study was to investigate changes in d13C dynamics in bulk soils, soil particle size-fractions, and in CO₂ from soils collected from 40-60 year old closed-canopy juniper (Juniperus virginiana) forest and paired C₄ grasslands. We hypothesized that a lifeform shift to juniper will alter quality, quantity, and distribution of SOC. We quantified the vegetation origin and cycling of new forest C and the vegetation substrate for microbial respiration by analyzing the d13C of soils and respired CO₂. d13C of SOC in forest soils indicates a large input of juniper-derived C to 10 cm. At 0-2.5 cm, 38% of SOC of the bulk soil is juniper in origin. In contrast, the majority of SOC in bulk soil below 10 cm is prairie-derived, residual carbon. Forest C is present in all size fractions but prevails in the >212 µm fraction. In grassland soils, d13C of respired CO₂ generally reflects the isotopic composition of bulk soil. In contrast, d13C of respired CO_{2_{from 0-10 cm depth in forest soils initially reflected the microbial utilization of new juniper humus (-25‰) from bulk soil. Thus, microbes preferentially utilized recent, C₃-derived juniper SOC. In summary, d13C data from bulk soils, particle size fractions, and microbial incubations confirm that fundamental vegetation shifts are altering the quality, and distribution of SOC.}}

Characterization of Microbial Communities in the Luquillo Experimental Forest Using Molecular Markers such as FAME and DNA.

Date Presented: Saturday Night

Lead Author: F. J. Rivera-Figueroa
Co-Authors: L. M., García-Orta, C. A. Cruz-Rodríguez, S. A. Cantrell
Institutional Affiliations: Universidad del Turabo, P. O. Box 3030, Gurabo, Puerto Rico 00778
Primary Site: LUQ

Abstract: Soil microorganisms live in complex communities. The identification using traditional cultural and physiological techniques has proven to be difficult and tedious. A small percentage (<10%) can be grown in culture and the true species richness is normally underestimated. Recently, new techniques using fatty acids methyl ester profiles and DNA have been developed to study soil microbial diversity. The microbial community tends to vary accordingly to the plant community structure and disturbances. In this project we are focusing in how the microbial community change through time and space (depth of 0-5 and 5-10 cm) along an elevation gradient that goes from a dry coastal to a lower montane dwarf forest. The other study focuses on how the microbial community responds to natural disturbances such as hurricanes. In order to study the changes and structure in the microbial community, we will extract Fatty Acids and DNA directly from the soil and leaf litter. The information given form these makers will help us understand the organization of microbial functional groups and its physiological status. We have found that fatty acids from eucaryotic cells (16:0, 18:2, 18:1 and 18:0) dominates in relative abundance over the groups of fatty acids such as 15:0, i15:0, a15:0, i17:0, a17:0 and i19:0, that are representative of bacterial communities in soil and leaf litter. Lipids like 18:2 and 18:1 have an abundance of 11% and 17% in leaf litter versus 1% and 7 % the soil, respectively. Bacterial branched fatty acids like i15:0 and a15:0 are more abundant in soil than leaf litter (8% and 4% vs. 2% and 0.7%, respectively). T

Characterization of regional crop dynamics using a modeling framework for management and visualization of information

Date Presented: Saturday Night

Lead Author: Stuart Gage
Co-Authors: Manuel Colunga-Garcia, Gene Safir, Steve DelGrosso, and Peter Grace
Institutional Affiliations: KBS LTER, Michigan State University. Colorado State University
Primary Site: KBS

Abstract: A research objective at the KBS-LTER is to examine how research on row crop agroecosystems at KBS represents crop production in the US Corn Belt. To facilitate this objective we developed a Modeling Applications System Integrative Framework (MASIF) which links an array of existing visualization, analytical, and data management software to manage model inputs and outputs as well as model execution. We are conducting three projects that demonstrate applications of MASIF. In the first project we want to characterize and analyze crop productivity in the North Central Region and explore future scenarios via modeling. We have conducted an analysis and comparison of historical observational data with outputs from crop simulation models. In the second project a crop model was calibrated to the cooler climate of the Upper Great Lakes Region. We tested the effects of temperature modifications and related that to the performance of the model. In the third project we have incorporated the DAYCENT model with MASIF to simulate regional sinks and sources of greenhouse gasses from agricultural soils including croplands and grasslands. We anticipate that simulations will provide information to decision makers for the assessment of economic, environmental and biophysical impacts of mitigation practices and policies.

Chronic Nitrogen Enrichment Affects the Structure and Function of the Soil Microbial Community

Date Presented: Friday Night

Lead Author: Serita Frey
Co-Authors: Melissa Knorr
Institutional Affiliations: University of New Hampshire
Primary Site: HFR

Abstract: We examined the effects of N enrichment on the relative abundance, diversity, and activity of bacteria and fungi in forest soils exposed to chronic nitrogen additions. During fall 2002 we collected and analyzed soil samples from the Chronic Nitrogen Addition Plots at Harvard Forest. One soil core (5.6 cm diam; O horizon plus 10 cm of mineral soil) was collected from four 5 x 5 m subplots within control, low N (5 g N m^-2 y^-1), and high N (15 g N m^-2 y^-1) plots in both a hardwood and pine stand. The samples were analyzed for active bacterial and fungal biomass, microbial functional diversity, and the activities of celluloytic and ligninolytic enzymes. We found that long-term N additions have decreased total microbial biomass, relative fungal biomass, functional diversity, and lignin-degrading activity. Total microbial biomass was 35 and 38% lower in the high N compared to control plots in the hardwood and pine stands, respectively. The proportion of the microbial community comprised of fungal biomass declined from 70-94% in the control plots to 45-53% in the high N treatments. Catabolic eveness, assessed by measuring the respiratory response of the microbial community to the addition of 25 different C sources, indicates that the functional or metabolic diversity of the microbial community is reduced under long-term N additions. Finally, the activity of phenol oxidase, a lignin-degrading enzyme, was significantly reduced by N enrichment, with a particularly strong effect observed in both the low and high N plots in the hardwood stand.

Climate (ClimDB) and Hydrology (HydroDB) Projects: Facilitating synthetic research and testing new web technologies

Date Presented: Friday Night

Lead Author: Don Henshaw
Co-Authors: Suzanne Remillard
Institutional Affiliations: USDA Forest Service, Pacific Northwest Research Station, Corvallis OR
Primary Site: AND

Abstract: The LTER Network faces significant challenges in strengthening existing cross-site research. Climatic and hydrological data are critical to these synthetic efforts and LTER Network sites and U.S. Forest Service (USFS) experimental watersheds are committed to populating and updating these basic data sets. The cross-site ClimDB and HydroDB projects facilitate synthetic research among this network of sites through production databases widely used in intersite comparisons, modeling studies, and land management-related studies. The ClimDB/HydroDB project features a data harvesting system, a central cross-site database, and a web interface to display, graph, and download data. The project allows individual sites to maintain local control of data in local information systems while also providing for the harvest, update, and public access to all site data through a common web interface at a central site. Site contributions have increased dramatically in the past year for air temperature, precipitation, and stream discharge, and all 24 LTER sites and an additional 8 USFS sites are participating. Visitors to the ClimDB/HydroDB web interface are increasing and average more than 500 visits per month, and the raw database includes over 5 million daily values from 18 separate measurement variables. ClimDB/HydroDB are key components to the LTER Network Information System and provide testing ground for new web technologies. Collaboration with the Georgia Coastal Ecosystems LTER site has allowed the harvest system to capture near real-time USGS hydrological data. Collaboration between the San Diego Supercomputer Center and LTER Network Office has explored and developed web services architecture as an alternative to the existing web harvester. The HydroDB database is also a proposed test-bed in an NSF Biological Database & Infrastructure proposal to develop advanced data processing services that enhance the network’s ability to integrate heterogeneous data sources.

CO2 Emissions from Jornada Basin Soils

Date Presented: Friday Night

Lead Author: Alfonso Serna-Perez¹
Co-Authors: H. Curtis Monger¹ and Jeffrey E. Herrick²
Institutional Affiliations: New Mexico State University¹ and USDA-ARS, Jornada Experimental Range²
Primary Site: JRN

Abstract: In arid and semiarid regions the calcium carbonate, exhumed by the erosive action of wind and water, might be a potential source of atmospheric CO2 when exposed to slightly acidic rain. An experiment was carried out at the Jornada LTER site in New Mexico to test this hypothesis. Daily soil CO2 flux was measured inside of chambers in three types of soils representing three different erosional states. Soda lime (60 g) and sodium hydroxide 0.4M (50ml), separately as methods, were used as the CO2 traps, and blanks were used to account for the atmospheric CO2. Soil CO2 flux (mg/cm2/day) was determined by weight difference for the soda lime and by titration for the sodium hydroxide. Rainfall and plant cover were also measured. In 2002, the highest values of soil CO2 flux, which occurred in the rainy season, were 2.28 mg/cm2/day for soda lime and 0.69 mg/cm2/day for sodium hydroxide. The lower values were found in fall (0.69 mg/cm2/day) for soda lime and in winter (0.14 mg/cm2/day) for sodium hydroxide. In general, no statistical increase in CO2 flux was detected in 2002 for soils with exposed carbonate horizons. However, individual analysis of blocks did detect statistical evidence of higher CO2 flux coming from the exhumed petrocalcic soil that might be attributed to the carbonate dissolution. Sampling period has been extended through 2003.

Community composition in space and time: examination of fauna and flora at Konza Prairie

Date Presented: Saturday Night

Lead Author: Dawn Kaufman
Co-Authors: Donald W. Kaufman, Glennis A. Kaufman
Institutional Affiliations: Kansas State University
Primary Site: KNZ

Abstract: As ecologists, we often seek to understand how biotas and communities are organized, how they are interrelated, and how they are affected by aspects of or changes in the environment. As environmental degradation or habitat fragmentation occurs, the suitability of islands, habitats, and patches (as well as the ability of individuals to move between islands, habitats, or patches) is affected; this has consequences for the distribution of species across these systems. At the Konza Prairie Biological Station (a 3500-ha tallgrass prairie site in the LTER system), a mosaic of discrete habitats (ranging in size from 6 ha to 230 ha) has been created by different fire disturbance regimes. Distributional data have been collected across the site and through time for various taxa, including groups of vertebrates, invertebrates, and plants. These detailed data enabled us to examine assemblages of different taxa for spatial and temporal structure within the context of a small region. We examined the relationship between assemblages found in different disturbance-mediated habitats. Our analyses were based on nested subset theory, in which a suite of assemblages is nested if the species compositions of successively less species-rich assemblages tend to be subsets of those assemblages that are more diverse. For example, long-term data for small mammals (from 14 local sites over 20 years) were utilized and assemblages exhibited a high degree of nestedness in space and time. This was true for individual years and sites, as well as for the entire study area and period, suggesting that movements between the habitat islands are important for maintenance of the overall fauna. Further, we compare results from Konza Prairie to preliminary results from other LTER sites and begin to form a pattern-based framework from which to examine community structure, environmental effects, and conservation implications.

Community Structure of Small Rodents and their Fleas on the Shortgrass Steppe:

Date Presented: Saturday Night

Lead Author: Dan Tripp
Co-Authors: Mike Antolin
Institutional Affiliations: Colorado State University
Primary Site: SGS

Abstract: Community Structure of Small Rodents and their Fleas on the Shortgrass Steppe: Abstract: Small rodents and their fleas are suspected to play an important role in the maintenance and transmission of wild rodent plague, Yersinia pestis, and Bartonella spp. in the western United States. Bartonella spp. have recently received increased attention as an emerging human pathogen that may be transmitted by fleas. Plague is known to cause large scale epizootics of black-tailed prairie dogs, Cynomys ludovicianus, often decimating entire colonies. To discern what role small rodents and their fleas play in disease transmission within and between rodent hosts, we compared fleas collected from rodents on prairie dog colonies to hosts in similar habitat adjacent to colonies, and habitat dominated by shrubs. Eighteen flea species were collected from fourteen rodent species and the degree of overlap was noted. The northern grasshopper mouse, Onychomys leucogaster, was captured in comparatively large numbers on all three habitats. It was the only rodent that showed significant overlap with other rodents in the fleas it carried (from five other rodent species). Diagnostic tests were conducted to determine the infection rates of plague and Bartonella spp. in both fleas and hosts.

Comparative and interactive effects of two keystone rodent species, prairie dogs (Cynomys gunnisoni) and banner-tailed kangaroo rats (Dipodomys spectabilis), on plants and animals in the northern Chihuahuan Desert

Date Presented: Saturday Night

Lead Author: Ana Davidson
Primary Site: SEV

Abstract: Prairie dogs and banner-tailed kangaroo rats are keystone species in semi-arid grasslands. Their burrowing and foraging activities are known to affect community composition and structure. In the American Southwest where these species co-occur, the relative effects of their activities on grassland ecosystems are unknown. Although prairie dogs and kangaroo rats appear to have similar functional roles, these species are ecologically different and have unique effects on grassland communities. This research evaluated their comparative and interactive influences on vegetation, burrow-dwelling arthropods, ground-dwelling arthropods, grasshoppers, lizards, and rodents at the Sevilleta Long-Term Ecological Research site in central New Mexico. Plant and animal community composition differed between disturbed mound patches and undisturbed non-mound areas, as well as between kangaroo rat and prairie dog mounds. Species and functional groups of species that associated with the mound habitats were more common at the landscape scale where both rodent species co-occurred compared to where only kangaroo rats occurred. The combined activities of prairie dogs and banner-tailed kangaroo rats generated disturbance patches of varying scale and intensity and enhanced landscape heterogeneity.

Comparative Observations of Long-Term Ecological Research Site Vegetation

Date Presented: Saturday Night

Lead Author: John Vande Castle
Primary Site: NET

Abstract: Remote Sensing data are used in this study to observe and compare changes in vegetation cover within and between sites of the U.S. Long Term Ecological Research (LTER) Network. In this study, vegetation index data products from the Moderate Resolution Imaging Spectroradiometer are used to look at seasonal changes in vegetation cover over regions of the LTER sites. The specific advantage of the MODIS data is the use of the Enhanced Vegetation Index Data (EVI) over the more conventional Normalized Difference Vegetation Index data (NDVI), particularly for cross-site comparisons. The results are also more reliable than previous estimates available from remote sensing data due to the calibration and validation of the data products. Vegetation changes seen in the MODIS EVI data for small regions of the research sites can also be dramatically different when expanded to a regional perspective. The MODIS data are also compared with historical Advanced Very High Resolution Radiometer (AVHRR) vegetation index data which provide a long-term perspective not yet present in the MODIS record. The perspective of the historical AVHRR estimates provides a much clearer picture of long-term vegetation changes, but the data are subject to calibration and other shortcomings. This works builds on previous research using single Landsat-Thematic Mapper scenes to compare the variance of vegetation patterns observed in data of the research sites.

Comparing plant cover estimation methods: visual cover estimation vs. point intercept method

Date Presented: Friday Night

Lead Author: János Garadnai
Co-Authors: György Kröel-Dulay, Barbara Lhotsky, Edit Kovács-Láng
Institutional Affiliations: MTA ÖBKI, Hungary
Primary Site: INT

Abstract: In plant ecology, there is often a need to estimate the cover of vegetation and plant species. Two methods widely used in plant ecology are visual cover estimation and point intercept method. We compared the ability of these two methods to estimate plant cover and species richness in an open grassland-shrubland mosaic in the KISKUN LTER, Hungary. Our research joins an EU-funded project (VULCAN), where the aim of the six participant countries is to study experimentally the effect of climate change on European shrubland ecosystems. We compare the point intercept method, which is the required method of the project, with the visual cover estimation method, which is widely used by Central-European researchers. To characterise the vegetation in study plots, we apply point intercept method along transects. The visual cover estimation was applied in quadrats along the same transects. We calculated species richness and cover by species at the transect and the plot level based on each of the two methods. We found that point intercept method detected considerably less species compared to visual cover estimation. Estimating the cover of the dominant secies (Populus alba, Festuca vaginata, Cynodon dactylon) the absolute values were different between the two methods, but the relative abundances were similar. The changes in cover of the dominant species through time estimated by the two methods were also similar. In contrast with visual cover estimation, point intercept method is able to detect the vertical structure of the vegetation (height, phytomass allocation), as well as phenological stage of plant organs (e.g. live or dead leaves). We conclude that neither method is superior over the other and the selection of appropriate method should be based on the research question asked.

Comparing trophic dynamics in urban and desert ecosystems using arthropod commmunities on brittlebush Encelia farinosa

Date Presented: Friday Night

Lead Author: Wendy A. Marussich
Co-Authors: Stanley H. Faeth
Institutional Affiliations: Arizona State University
Primary Site: CAP

Abstract: Do trophic dynamics differ in urban vs. ‘natural’ systems? Is trophic structure controlled by ‘top-down’ (natural enemies) or ‘bottom-up’ (limiting nutrients) forces in these systems? To address these questions, we have established long-term arthropod monitoring experiments on brittlebush (Encelia farinosa) at two permanent urban CAP-LTER study sites (President’s House and Desert Botanical Gardens) and one desert preserve (Usery Mountain Park). Brittlebush was selected because it is a common native desert perennial that is often used in urban landscaping. We are sampling the arthropod community and plant damage once per month, applying a water treatment every two weeks, and measuring plant volume and biomass accumulation four times per year. Arthropods are being identified to family and feeding-guild. By using the CAP-LTER permanent sites we can link these experiments to other CAP-LTER core areas by quantifying changes in ecosystem function with trophic complexity and patch type. Ultimately, we will combine our experimental results with a patch dynamic model to better understand how inter-patch differences in trophic dynamics impact regional fluctuations in plants, herbivores, and predators.

Comparison of spring annual seed bank diversity relating to Dipodomys spectabilis mounds

Date Presented: Saturday Night

Lead Author: Terri Koontz
Co-Authors: Heather Simpson
Institutional Affiliations: Sevilleta LTER, UNM Biology Dept.
Primary Site: SEV

Abstract: Disturbance is a major factor in determining the spatial structure and temporal dynamics of ecological systems. Many studies have been conducted concerning the plant assemblages around Dipodomys spectabilis mounds compared to the inter-mound area. These studies have shown that annual plant cover is higher on kangaroo rat mounds compared to inter-mound areas. However, few studies have addressed the affects of disturbance on the soil seed bank. Soil seed banks are an important component of the plant community particularly in arid environments. Annual plants have been known to create viable seeds that remain dormant in the soil for many years making their seed bank a persistent one. A persistent seed bank allows for future recruitment of plants given favorable conditions and could likely have a dramatic impact on the overall species diversity of the community. Our study addresses the seed bank of the spring annual plant community around these disturbed areas on the Sevilleta. Our question is: Does the spring annual seed bank differ from the mound area compared to the inter-mound area? D. spectabilis provides a suitable environment for spring annuals to reach maturity and develop an abundance of seeds that are then deposited in the surrounding mound area. Thus, we predict that the mound area will have a higher number of seeds and species diversity compared to inter-mound areas.

Connecting communities with their watersheds and coastal oceans through integrated environmental education

Date Presented: Saturday Night

Lead Author: Ali Whitmer
Co-Authors: Jenifer Dugan
Institutional Affiliations: Marine Science Institute, University of California, Santa Barbara
Primary Site: SBC

Abstract: The K-12 outreach and informal education programs at the Santa Barbara Coastal LTER (SBC-LTER) focus on developing educational materials and activities that center on the importance of our watershed resources, the connections between watersheds and coastal ecosystems, and how human activities can affect these ecosystems. We accomplish this through collaborations with the South Coast Watershed Resource Center, the Marine Science Institute and local area teachers in developing 1) a virtual tour of a local watershed that includes an interactive creek runoff animation, a satellite image-based virtual tour of an local watershed, and discussion of the natural history of the wathershed zones and plant and animal communities; and 2) standards-based lesson plans developed by middle-school science teachers involved in SBC-LTER research, which connect to; 3) hands-on activities conducted on a “floating lab,” a 75-foot, high-speed catamaran that has been outfitted for educational cruises to the Santa Barbara Channel. Through this integrated program, the SBC-LTER reaches teachers, hundreds of students and the general public educating them about the on-going research on valuable resources in their local environment.

Controls on oligohaline marsh macrophyte zonation and production within a New England estuary (Plum Island Ecosystem LTER)

Date Presented: Saturday Night

Lead Author: Robert J. Daoust
Co-Authors: James T. Morris
Institutional Affiliations: University of South Carolina
Primary Site: PIE

Abstract: Zonal patterns exhibited by estuarine macrophyte communities have long fascinated ecologists. Originally believed to be the sole result of strong salinity gradients present in these systems, recent research suggests that these patterns are the combined result of species-specific stress tolerance and competitive ability to acquire limiting nutrients. This research, however, has focused on saltmarshes with little work in upstream, oligohaline marshes. Oligohaline marshes are inherently more complex than their downstream neighbours since nutrient availability and salinity fluctuates on seasonal and tidal scales. We conducted factorial fertilization studies within oligohaline and salt marshes at the PIE LTER which show that the dominant macrophyte in each system responds to different limiting nutrients (nitrogen in saltmarshes and phosphorus in oligohaline marshes). This fact further complicates possible controls on macrophyte zonation in oligohaline systems where both brackish and saltmarsh species co-exist. To investigate how nutrients and stress tolerance control zonation within oligohaline marshes we employed reciprocal transplants nested within a factorial N+P fertilization experiment. In addition, we analysed samples of the two dominant co-occurring species for osmolyte concentrations to assess the importance of stress tolerance in determining which nutrient limits production. Our results indicate that species-specific responses to nutrient additions exist, suggesting that both nitrogen and phosphorus locally control production. The reciprocal response, however, was stimulated by fertilization and the brackish species performed significantly better when transplanted and fertilized with its preferred nutrient than its saltmarsh neighbour. Thus, changes in nutrient loading into estuaries will directly affect the distribution and zonation of oligohaline macrophyte communities and the importance of phosphorus in coastal systems is currently underplayed.

Crop uptake, nitrification, and denitrification in a continuous corn agroecosystem

Date Presented: Saturday Night

Lead Author: Claire McSwiney
Co-Authors: G. Philip Robertson
Institutional Affiliations: W.K. Kellogg Biological Station and Michigan State University
Primary Site: KBS

Abstract: One of the most important proximal controls on N2O production in soils is N availability. In studies conducted at the W.K. Kellogg Biological Station in southwest Michigan in 2001 and 2002, we determined that N2O fluxes measured across a high resolution N gradient were moderately low (< 50 g N2O-N ha-1 day-1) up to 101 kg N ha-1 additions where grain yields were maximized, after which fluxes increased sharply. Two mechanisms that might explain the nonlinear response in N2O production to incremental N addition are differential uptake of N by the crop and changes in microbial processes responsible for N2O production across the N gradient. In 2003, N, as granular urea, was applied at nine levels from 0-292 kg N ha-1 yr-1 to 4 replicate fields in continuous corn and then incorporated. Plots were irrigated to alleviate water stress in the corn crop. We measured surface N2O fluxes after fertilization in plots where the corn was removed and in plots where the crop was left intact. Nitrification and denitrification assays were conducted to determine the relative importance of each of these processes in N2O production across the N gradient. Corn yields were determined at harvest and soil mineral N was determined at each flux measurement. The N2O flux response to the fertilizer gradient was linear in plots without corn and was nonlinear in plots with the crop.

Culturally Responsive Environmental Science Education

Date Presented: Friday Night

Lead Author: Elena Sparrow
Co-Authors: Sidney Stephens and Leslie Gordon
Institutional Affiliations: School of Natural Resources & Agricultural Sciences, University of Alaska Fairbanks for first and second authors and School of Education, University of Alaska Fairbanks, for the third author.
Primary Site: BNZ

Abstract: A culturally responsive environmental science education model is emerging that integrates traditional ecological knowledge (TEK) with science instruction and research investigations aimed at enhancing student science interest and skills, cultural well-being, environmental science knowledge and awareness of climate change issues important to their community. The model is being developed through the “Observing Locally, Connecting Globally (OLCG) or Global Change Education Using Western Science and Native Observations program funded by NSF. Both knowledge systems and best teacher practices are used in professional development that prepares pre-college teachers for engaging their students in environmental science investigations relevant to their community. The OLCG Institute is begun with a two-day field trip, observing the environment and changes along the river, and listening to Native experts who share their holistic and interrelated system thinking, and TEK that comes from their long-term observations and living on the land. Participants also learn and practice scientific measurements in the areas of atmosphere/weather, hydrology, soils, land cover/biology and phenology, developed by the Global Learning and Observations to Benefit the Environment (GLOBE) program and by some Alaska climate change researchers. Best classroom practices that include inquiry learning in science, learning cycle model, establishing a constructivist learning environment, teaching and assessing to standards, and teaching and assessing for diversity, are discussed and modeled during the Institute. Teachers are provided scientific instruments, a website http://www.uaf.edu/olcg, educational materials and curriculum that are standards based and culturally responsive, and continued support throughout the year as they implement in their classrooms. Environmental science is taught and learned by actively involving students in the science process in local environmental change research.

Decomposing a Correlation between High Temperature and Low Income at a Neighborhood Scale with Thermal Infrared Imagery in Phoenix, Arizona

Date Presented: Friday Night

Lead Author: Lela Prashad
Co-Authors: William L. Stefanov, Anthony Brazel, Sharon Harlan, Nancy Jones
Institutional Affiliations: Arizona State University
Primary Site: CAP

Abstract: Initial results from a CAP LTER 2003 study at the census tract scale in Phoenix found a positive correlation between high mean temperatures and low-income, Hispanic neighborhoods (Jenerette, et al., 2003). The two purposes of our study were: 1) to decompose this finding at a finer, neighborhood scale by measuring temperatures from surface materials with thermal infrared (TIR) remotely sensed (RS) imagery and 2) to determine the utility of a range of TIR RS imagery at this scale. The eight neighborhoods in our study range from high to low-income. The low-income neighborhoods are predominantly Hispanic and are located in the urban core. RS images were processed from Landsat, nighttime ASTER, and MASTER sensors to convert radiance to temperature for the eight neighborhoods. The three types of imagery were selected for their varying resolutions and times of acquisition. The 30m Landsat scenes were too coarse to be effective in delineating temperature differences within a neighborhood but were useful in providing an overall mean temperature. The 12.5m MASTER imagery was the most useful in highlighting temperature variation within a neighborhood. The nighttime ASTER imagery proved effective in determining the contribution of the thermal inertia of the materials within a neighborhood to a local heat island effect.

Decomposition in the forest-alpine tundra ecotone of the Colorado Front Range.

Date Presented: Saturday Night

Lead Author: Robert L Sanford Jr
Co-Authors: Cynthia L Withington
Institutional Affiliations: University of Denver
Primary Site: NWT

Abstract: Nitrogen (N) and phosphorus (P) availabilities strongly influence alpine plant productivity, yet much uncertainty exists about nutrient availability in the forest-alpine tundra ecotone. The availability of these elements is believed to vary directly with organic turnover and decomposition. Cotton strip assay was used to measure cellulose decomposition through loss of tensile strength of cotton strips (CTSL). Control, P-enriched, and N-enriched strips were left to degrade in the surface soil of forest, krummholz, and tundra plots for one year. Four transects spanning the forest-tundra ecotone, at two sites (Mt. Evans and Niwot Ridge) along the Colorado Front Range were used for experimentation. From preliminary analysis, the alpine tundra appears to have greater rates of decomposition than the subalpine forest or krummholz zone. In the forest, nitrogen enriched strips seem to be most decomposed while the P-enriched strips appear most decomposed in the krummholz. Our initial results suggest nitrogen limitation in the subalpine forest and phosphorus limitation in the krummholz zone.

Denitrification in watersheds with discontinuous permafrost of the boreal forest of interior Alaska

Date Presented: Friday Night

Lead Author: Jonathan O'Donnell
Co-Authors: Jeremy B. Jones
Institutional Affiliations: Institute of Arctic Biology University of Alaska Fairbanks
Primary Site: BNZ

Abstract: In boreal forest watersheds of interior Alaska stream chemistry varies considerably among catchments with varying extents of permafrost. Permafrost confines groundwater flow to shallow soil horizons, where organic matter storage and microbial activity are high. In permafrost-free watersheds, groundwater flows through deeper mineral horizons, where organic carbon is potentially immobilized and microbial activity is lower. In Caribou-Poker Creeks Research Watershed in interior Alaska (Bonanza Creek LTER), stream export of nitrate appears to be inversely related to permafrost extent. In a high permafrost watershed, inorganic N export was 5972 mol N km^-2 yr^-1, compared to 9499 mol N km^-2 yr^-1 in a low permafrost watershed. This observation suggests that high permafrost watersheds are more effective at retaining nitrogen through denitrification, plant uptake, or microbial immobilization. We investigated the role of denitrification in regulating nitrogen exports in boreal forest streams. Denitrification rates were measured in riparian soils of two catchments with varying extents of permafrost. We used the isotope pairing technique and the acetylene block to estimate denitrification rates in the field. To examine the mechanisms that control denitrification, laboratory incubations were conducted whereby soils were amended with either nitrate or labile organic carbon. Groundwater was sampled along lateral flowpaths to assess changes in nitrate and carbon from upland to riparian areas. Field incubations and analysis are currently in progress and will be discussed.

Detecting changes in Atlantic lagoonal salt marsh habitat using current and historic aerial imagery

Date Presented: Saturday Night

Lead Author: R. M. Erwin
Co-Authors: Geoffrey Sanders and Diann Prosser
Institutional Affiliations: University of Virginia and U.S. Geological Survey Patuxent Wildlife Research Center
Primary Site: VCR

Abstract: Average rates of relative sea-level rise (RSLR) along the mid-Atlantic coast are higher than the global eustatic rate of 1.5-2.0 mm/yr, with relative rates ranging from about 2.5 mm/yr to 4.0 mm/yr. Data ranking RSLR against marsh elevation change suggest that marshes inside the mid-Atlantic barrier islands may not be keeping pace with rising seas. In an attempt to assess how such processes have affected salt marsh habitat structure over time, we use a geographic information system (GIS) to analyze salt marsh habitat change in three regions along the Atlantic Coast (Cape Cod, MA, Southern New Jersey and the Eastern Shore of Virginia). Aerial photography from three time periods was collected for each location, georeferenced and digitized. All locations, except for one site in Virginia, experienced a net loss of salt marsh due to erosion along the marsh edge, widening of tidal creeks and increased interior ponding. We found large amounts of gain at one site in Virginia due to the expansion of salt marsh into what was historically a tidal flat. The cause of these changes cannot be determined from the geographic analysis alone. Accordingly, we are currently monitoring marsh elevation change and sediment accretion at each site to help determine the processes leading to these changes.

Determination of the minimal glucose amendment for maximal initial respiratory response of soil organisms using substrate induced respiration.

Date Presented: Saturday Night

Lead Author: Marcela Zalamea
Co-Authors: Grizelle González
Institutional Affiliations: University of Puerto Rico, Río Piedras, PR; USDA Forest Service, International Institute of Tropical Forestry, Río Piedras, PR
Primary Site: LUQ

Abstract: Substrate induced respiration (SIR) is used for estimating microbial biomass on soils. In this technique, an easily assimilated substrate(usually glucose) is added to the sample and the respiration response (O2 uptake and CO2 evolution rates) is measured. In soil amendments, it is assumed that the initial maximum respiration rate is proportional to the microbial biomass present. To apply this method, it is necessary to know the minimum glucose concentration required to achieve a maximal respiration response. This concentration varies greatly between sites and must be determined for each location. The objectives of this study were: 1)to determine the amount of glucose needed for maximum microbial stimulation for soils in a lowland moist forest of Puerto Rico, 2)to establish the time necessary for stabilization of the soil sample after administration of the amendment treatments and 3)to estimate the microbial biomass on the basis of the respiration rate. Incubations were done in an Oxymax ER-10 respirometer during 15 hours at 25 oC, 800.2 mmHg and 55% of WHC. Glucose concentrations used were: 1, 2, 3, 4, 5, 7 and 8 mg C-glu g-1 soil. Maximum initial respiratory response was obtained for 3 mg C-glu g-1 dry soil, after 6.64 and 7.87 hours of incubation for CO2 and O2, respectively. The maximal O2 uptake rate for this treatment and time was -29.754 µg g-1 dry soil h-1 (S.E = 4.81) and the CO2 evolution was 19.28 µg g-1 dry soil h-1 (S.E = 1.55). Microbial biomass estimations range between 129.6334 µg biomass-C g-1 dry soil (S.D = 2.21) and 621.099 µg biomass-C g-1 dry soil (S.D = 10.57) depending on the equation applied (conversion factors vary between 16 and 40). A minimum time of 6 hours is required for the samples to stabilize, which means less variables readings of CO2 and O2 rates. We recommend that respiration rate measurements should be taken after a stabilization period. Currently, experiments are being performed to confirm and support these results.

Determining the physiological response of a subtropical seagrass, Thalassia testudinum, to salinity stress using pulse amplitude modulated (PAM) fluorometry

Date Presented: Friday Night

Lead Author: Dottie Byron
Co-Authors: James Fourqurean
Institutional Affiliations: Florida International University
Primary Site: FCE

Abstract: As the Everglades ecosystem is restored to near its historic flow regime, water quality within Florida Bay will be affected. Currently conditions within Florida Bay vary between hypersaline and hyposaline, depending on location within the bay and time of year. In response to a change in Bay water quality, the benthic communities (i.e. the seagrass community) may shift from the Thalassia testudinum dominated ecosystem that currently exists. Physiological changes, such as amino acid concentration, chlorophyll a:b ratios, soluble carbohydrates, stable carbon isotope ratios and fluorescence values occur much earlier then growth and morphological changes for seagrasses in response to stress. Short and long-term stress experiments to determine if T. testudinum can acclimate to dramatic changes in salinity may aid in predicting changes in species dominance. This project investigates how fluorescence measurements obtained with a pulse amplitude modulated (PAM) fluorometer change in response to salinity changes that may be stressful for T. testudinum. This project also investigates the physiological state of T. testudinum within Florida Bay in response to salinity gradients as part of the Florida Coastal Everglades LTER project.

DEVELOPING SOUTH AFRICA’s ENVIRONMENTAL OBSERVATION NETWORK (SAEON)

Date Presented: Friday Night

Lead Author: Johan Pauw
Primary Site: INT

Abstract: The rationale for a SAEON evolved from the Long-Term Ecological Research (LTER) paradigm that strives to overcome the limitations of normal environmental research which is mostly done in too short time frames on too small areas and focusing on too few variables to provide reliable answers within the context of ecological time and large ecosystems. Our vision is to establish an observation and research network that provides the understanding, based on long-term information, needed to address large-scale environmental issues. We aim to create a framework that permits collection, transmission and interpretation of data on slow variables in distributed network of observatories. The new understanding brought about through SAEON will inform suitable policies and appropriate actions for dealing with the inevitability of environmental change and its consequences for the livelihoods of South Africans. The core research framework of the SAEON is directed at studying the stressors of ecosystems such as climate change, land-use and settlement changes, eutrophication of the biosphere and the responses of ecosystems to these stressors as measured in its biodiversity, productivity and nutrient fluxes. Societal changes with regards to population growth and health, macro-economic vectors, institutional structures and technological advances/assimilation and how these influence ecosystem biodiversity and hydrology will become important new directions in environmental research. The SAEON will inform national programmes and policies directed at securing the competitiveness of the environment and sustainable development. It will enhance the ability to meet the requirements of international conventions (CBD, CITES, CCAMLR, RAMSAR, FCCC, CCD, etc.). This will also empower the public to participate fully in assessing the consequences of local, regional and national environmental and developmental scenarios as facilitated through the SAEON's education and outreach programmes.

Development of a National LTER Network for Finland

Date Presented: Friday Night

Lead Author: Juha Kämäri
Co-Authors: M. Forsius, L. Arvola, A. Järvinen, Y. Viisanen, E. Leskinen, L. Finér, P. Hari, H. Raitio, J.Salo
Institutional Affiliations: Finnish Environment Institute, University of Helsinki, Finnish Meteorological Insitute, University of Oulu, University of Joensuu, Finnish Forest Research Institute, University of Turku
Primary Site: INT

Abstract: Several research institutions in cooperation with the Research Council for Biosciences and Environment have been developing the rationale for LTER in Finland. The institutions have been encouraged to come up with a proposal for a national LTER network. Initiatives for national LTER sites were collected in spring 2003. The seven sites that were initially identified maintain high quality infrastructures that enable long-term ecological research with a focus on complex interactions between environmental pressures (climate change, land use change, atmospheric pollution) and ecosystem functions and services. The sites cover a wide range of ecosystems and human induced pressures: 1. Kilpisjärvi-Kevo Arctic Ecosystems 2. Pallas-Sodankylä: Subarctic Fell Ecosystems 3. Bothnian Bay: Northern Coastal Ecosystems 4. Joensuu-Kuhmo-Oulanka: Northern Boreal Forest Ecosystems 5. Hyytiälä-Parkano-Vilppula: Southern Boreal Forest Ecosystems 6. Lammi-Evo-Konnevesi: Southern Boreal Freshwater Ecosystems 7. Seili-Husö-Tvärminne: Coastal and Archipelago Ecosystems LTER in Finland will have objectives similar to that of the existing ILTER network with particular emphasis on objectives related to (i) understanding long-term trans-boundary ecological phenomena; (ii) facilitating national and international collaboration, and (iii) promoting comparative analysis on a European scale. The Finnish LTER sites will be developed into multi-functional research platforms and should include ecological and socio-economic dimensions.

Development of a simulation environment for the management and visualization of information from simulation models applied to a regional scale

Date Presented: Saturday Night

Lead Author: Stuart Gage
Co-Authors: Manuel Colunga-Garcia, Gene Safir, Jiaquo Qi, Asif Prasla
Institutional Affiliations: KBS LTER, Michigan State University
Primary Site: KBS

Abstract: Simulation of physical and biological phenomena at multiple time and space scales is playing a pivotal role in areas that range from genetic studies to global change analysis and assessment. Regional simulation models require the use of large data inputs and are evolving in scope and sophistication. A Modeling Applications System Integrative Framework (MASIF) is presented as a method to facilitate utilization of large amounts of spatial-temporal outputs from regional scale simulations. MASIF incorporates commercial software that provide the model analyst with the ability to rapidly summarize and analyze model results. MASIF enables visualization of model input data, model simulation results, and computation of statistical patterns of information associated with model inputs and outputs. In developing MASIF we have adopted a modular approach that allows the coupling of a model to the analysis and mapping framework using either executable model code or raw computer instructions, and the parameters files. We are currently enabling MASIF to accommodate satellite remotely sensing data as a driver to calibrate model predictions during simulation. For example, we use remote sensing information to adjust simulated biomass or LAI output from daily crop growth. The MASIF environment provides a powerful and flexible environment that allows model analysts to conduct creative regional experiments with either complex or simple regional models. By providing models with a robust user interface, modelers can optimize their efforts and concentrate on model development. We recognize the value of stand-alone and network-based analytical environments for model assessment and application and thus envision the potential to run, analyze, and visualize web-based simulation models.

Diatoms as Indicators of Water Quality in a Tropical River in Northeast Puerto Rico

Date Presented: Saturday Night

Lead Author: Brynne Bryan
Primary Site: LUQ

Abstract: Using diatoms as indicators of trophic status of rivers is becoming a popular tool for water quality managers in the United States and other countries with temperate climates. Similar criteria have not been developed for tropical systems. Most of what little that is known about diatom communities in the Caribbean comes from surveys conducted in the late 1800’s. A preliminary study along the Rio Mameyes revealed that shifts in community structure correspond with changing concentrations of nutrients, similar to the response of communities in temperate regions. The proposed project will include analyses of the diatom communities in several major rivers that drain geologically distinct watersheds in Puerto Rico. The purpose of this study is to determine how Puerto Rican freshwater diatom species respond to varying nutrient concentrations, to check these responses experimentally in an artificial mesocosm, and to develop the most economically efficient protocols for processing samples.

Diel and Seasonal Patterns of Benthic Fluxes of Nutrients, Gases and Dissolved Organics from Temperate Intertidal Sediments of Georgia and South Carolina

Date Presented: Friday Night

Lead Author: William Porubsky
Co-Authors: Nathaniel Weston, Samantha Joye, Rosalynn Lee
Institutional Affiliations: University of Georgia
Primary Site: GCE

Abstract: Incubations of sediment cores were used to quantify benthic fluxes of nutrients, dissolved gases, dissolved organics, and reduced constituents in temperate intertidal sediments in Georgia and South Carolina. Sediment flux cores (n=2-4) were collected seasonally at each site, incubated at in situ temperatures for at least 72 hours, and sampled at 12 hour intervals. Light/dark incubations were performed to evaluate the impact of benthic primary production on benthic fluxes. Benthic chlorophyll concentrations and rates of gross photosynthesis illustrated that sediments were very productive. Benthic phototroph activity limited the efflux of both N and P. Oxygen concentrations in the overlying water decreased over the incubation (dark treatments) and fluxes of PO₄^3-, Fe²⁺, and NO_x exhibited a strong correlation to oxygen concentration. During dark incubations, there was little nutrient efflux from sediments with a microalgal cap and even during prolonged dark incubations, efflux occurs only after sediments become anoxic. N₂ and N₂O fluxes illustrated high denitrification rates that were correlated with photosynthesis activity and redox (oxic/anoxic) conditions. During the winter and summer of 2002, ¹⁵NO₃^- tracer studies were used to evaluate the fate of NO₃^- at these sites. NO₃^- availability appeared to limit benthic primary production as shown by a large uptake of Si following NO₃^- addition. Additional evidence suggests that the NO₃^- in the dark treatments was not only utilized by denitrifiers, but also by microorganisms carrying out dissimilatory nitrate reduction to ammonium. These results demonstrate the dynamic nature of materials fluxes on both large (seasonal) and small (diel) time scales and underscores the role of benthic primary producers in influencing benthic flux patterns.

Differences in growth, water use and hydraulic constraints on small and large Larrea tridentata

Date Presented: Saturday Night

Lead Author: Juliana Medeiros
Co-Authors: Will T. Pockman
Institutional Affiliations: University of New Mexico
Primary Site: SEV

Abstract: Despite the apparent advantages of conservative water use for desert plants, several studies have shown that establishing individuals of woody desert perennial species are much less conservative in their water use than adults. Maintaining high rates of water loss during times of high water availability could allow small plants to take advantage of pulses of water, such as the summer monsoons typical of warm deserts like the Chihuahuan, and thereby become established quickly. However, a plant cannot endlessly increase water loss in order to grow faster; there are hydraulic constraints on rates of water loss. The hydraulic properties of a particular soil microsite and plant xylem, as well as the AR:AL (absorbing root area to transpiring leaf area ratio), interact to set limits on rates of water loss. If transpiration rates become too high, cavitation may limit the ability of the soil and xylem to supply water to the leaves. We tested two hypotheses on small and large plants in a population of Larrea tridentata located at the Sevilleta LTER in central New Mexico: (1) do small plants grow faster and use water less conservatively than large, and (2) are there differences in the hydraulic constraints on small and large plants. Shoot growth, gas exchange and plant and soil water potentials were measured in the field to determine growth rates, water status and water use from April 2002 – August 2003. Measurements of leaf specific conductance determined the ability of the xylem to supply water to the leaves. A model (Sperry et. al, 1998) determined the hydraulic constraints on each size based on xylem vulnerability curves and soil texture analysis. Excavation findings were used to estimate (AR:AL) for the model. Results indicate that, though the two sizes did not differ significantly in predawn or midday water potential, small plants had significantly higher rates of morning transpiration as well as photosynthesis, transpiration and conductance at midday(alpha=0.5).

Differential Effects of Soil and Substrate Nitrogen on Leaf Litter Decomposition in Two Puerto Rican Forests

Date Presented: Saturday Night

Lead Author: Heather E. Erickson
Co-Authors: Patricia Soto Oliver, Jana E. Compton
Institutional Affiliations: Universidad Metropolitana, U.S .Environmental Protection Agency - Western Ecology Lab
Primary Site: LUQ

Abstract: Soil nitrogen (N) availability can stimulate, inhibit or have a neutral effect on leaf litter mass loss, while litter N often correlates positively with mass loss, especially in the early stages of decay. Less studied, is the effect of litter or soil N on changes in natural abundances of 15N during decay. We conducted a litter transplant experiment for 160 days in two tropical forests of contrasting soil and litter N availabilities. Mixed species litters from the two sites were decomposed in litterbags to examine effects of soil and litter N on mass loss, N dynamics and changes in del 15N during decay. Mass loss was the same across site and litter source (mean ~ 45%). Thus, because both litters had high initial lignin (mean = 26.6%), a lignin, rather than a litter or soil N, control of early phase mass loss is suggested. In contrast, N dynamics were independent of litter chemistry and may have been related to soil differences (possibly N availability); both types of litter lost proportionally more N at the low N site than at the high N site, likely reflecting a greater demand for N at the low N site. However, litter chemistry appeared to influence del 15N dynamics and this was independent of whether N was released during decomposition; net 15N enrichment occurred when the low N (1.1%)litter released N but not when the high N (1.8%) litter released N. Thus, soil N availability and litter chemistry appear to have important and unique effects on the decomposition process in these tropical forests.

Direct and indirect effects of fire on shrub expansion in a mesic grassland

Date Presented: Saturday Night

Lead Author: Jana L. Heisler^1,2
Co-Authors: John M. Briggs¹, Alan K. Knapp², John M. Blair,² and Amy Seery²
Institutional Affiliations: Arizona State University¹, Kansas State University²
Primary Site: KNZ

Abstract: Determinants of the balance between grass and woody vegetation in grasslands and savannas have received considerable attention because of the potential for dramatic shifts in ecosystem structure and function that can occur as one growth form replaces the other. We studied a mesic grassland ecosystem in which recently established “shrub islands” are expanding due to fire suppression. The objective of this research was to assess the direct effects of fire vs. alterations in resource availability (N and light) that accompany fire, as mechanisms that constrain or facilitate shrub (Cornus drummondii) expansion. The primary effects of fire in 2001-2002 were 100% aboveground mortality of shoots of C. drummondii and removal of the detrital layer. Post-fire resprouting resulted in ca. a 600% increase in stem density compared to a 200% increase observed in unburned shrub islands. The addition of a litter layer to burned shrub islands reduced soil temperature and light availability (similar to unburned islands) but stem density still increased by ca. 400%. In contrast, N additions did not influence new stem production or ANPP. While two years of fire did not impact total ANPP in shrub islands, it did shift the relative abundance of growth forms. Grass productivity was stimulated by the high light conditions of the post-fire environment while C. drummondii ANPP was reduced. In unburned shrub islands, C. drummondii ANPP was greatest, whereas a reduction was observed in graminoid ANPP. The persistence of woody vegetation along with a significant reduction in grass ANPP (ca. 30%) suggests that once established, C. drummondii can exclude C4 grasses and that an important ecological threshold has been crossed. While restoring fire to mesic grasslands may prevent conversion to shrub/woodland, the abundance of shrubs is likely to remain unchanged with community structure co-dominated by multiple growth forms in the future.

DISSOLVED ORGANIC CARBON IN SOILS, STREAMS, AND LAKES OF AN ARCTIC CATCHMENT: LINKING BIOAVAILABILITY, CHEMISTRY, AND MICROBIAL COMMUNITY COMPOSITION

Date Presented: Friday Night

Lead Author: Kristi Judd
Co-Authors: Byron Crump, George Kling
Institutional Affiliations: University of Michigan Department of Ecology and Evolutionary Biology, Univeristy of Maryland Center for Environmental Science, University of Michigan Department of Ecology and Evolutionary Biology
Primary Site: ARC

Abstract: In arctic catchments, thick organic soils and a permafrost boundary result in high inputs of dissolved organic matter to aquatic systems. These inputs are important in fueling aquatic microbial foodwebs. The extent to which terrestrial dissolved organic carbon (DOC) is available to support aquatic microbial growth depends on its bioavailability which may differ with the source of the DOC within the catchment and seasonally. To better understand the major controls on DOC bioavailability and microbial activity, we examined patterns of microbial community composition and DOC chemistry in an arctic catchment and conducted experiments to determine the relative importance of these two factors in controlling carbon processing. Both DOC chemistry and microbial community structure (phospholipid fatty acids) differed between tussock, birch-willow, and wet sedge soils. In mesocosm experiments, up-slope DOC was added to microbial inoculi, and microbial production was measured over the course of four weeks. We measured DOC chemistry (phenolics, simple carbohydrates, and amino acids) and microbial community composition (denaturing gradient gel electrophoresis (DGGE)) at the beginning and end of the experiment. When water from an up-slope source was added to microbial communities, microbial production was similar to microbial production of the source water community. Addition of both wet sedge and tussock soil water DOC to down-slope surface water communities (small stream and lake) greatly increased microbial production. Addition of stream water to a lake inoculum, however, depressed microbial production of lake water microbes. Over the course of the experiment microbial community composition shifted in the direction of the microbial production of the DOC source community, and the addition of soil water DOC had the strongest effect. These results suggest that DOC chemistry strongly drives the structure and function of microbial communities in arctic tundra systems.

Distribution and Temporal Changes of Vegetation in Mt. Sorak Biosphere Reserve, Korea

Date Presented: Friday Night

Lead Author: Do-Soon Cho
Co-Authors: Il-Yop Lee, Kyu-Song Lee
Institutional Affiliations: Dept. of Life Sciences, The Catholic University of Korea1, Dept. of Biology, Kangnung National University2
Primary Site: INT

Abstract: Distribution of trees and herbs and temporal changes in the vegetation structure over the last 5 years were studied in the Mt. Sorak Biosphere Reserve in central Korea. To investigate the growth and mortality of trees, eighteen 10m X 20m rectangular permanent quadrats were established in Inner Sorak, and 16 quadrats of the same size were established in Outer Sorak in 1997. The density of trees within the permanent quadrats was highest in the order of Quercus mongolica, Pinus densiflora, and Acer pseudosieboldianum. Size-frequency distribution of major tree species showed that shade-intolerant Quercus mongolica is regenerating well, while extremely shade-intolerant Pinus densiflora is expected to decrease in the near future. There were little changes in the species composition in the permanent quadrats for the last five years. Many uncommon species showed little recruitment into tree classes. 12.9% of all the trees of 1997 died between 1997 and 2002, while 7.6% of all the trees of 2002 had been newly recruited into tree classes for the same period of time. About 90% of dead trees were in the smallest size classes (i.e. DBH < 10.0cm). Total density of trees declined by 7.2%, but the mean DBH increased by 0.9% for the last 5 years. Among the common species from the studied quadrats, Lindera obtusiloba showed the highest mortality of 48.8%, and Pinus densiflora had the mortality rate of 32.1% for the same period. In contrast, the highest recruitment rate of 9.7% was occurred in Acer pseudosieboldianum. The results of this study showed that there had been few large natural or artificial disturbances in the studied quadrats, and little static changes occurred as a result, but that dynamic changes in the vegetation structure due to mortality and recruitment at the level of saplings occurred very actively in Mt. Sorak even within a relatively short period of time.

Diversity and spatial heterogeneity of ectomycorrhizal fungi in oak savannas

Date Presented: Friday Night

Lead Author: Ian A. Dickie
Co-Authors: Peter B. Reich, Stefan A. Schnitzer, David J. McLaughlin, Sarah E. Hobbie
Institutional Affiliations: University of Minnesota
Primary Site: CDR

Abstract: Oak savannas are unique, spatially heterogeneous ecosystems, codominanted by ectomycorrhizal trees and arbuscular mycorrhizal prairie grasses and forbs. These ecosystems are critically endangered, with, for example, only 0.02% remaining of the original oak savannas of the Midwestern region of North America. In a series of studies, we examined the belowground ectomycorrhizal fungal diversity of oak savannas, the effect of fire on diversity, and the spatial heterogeneity of ectomycorrhizal fungi as related to distance from trees. We have found more than 130 unique RFLP-types in belowground sampling. Although belowground diversity is higher in closed-canopy forests than savanna, frequently-burned savannas contain a number of species of fungi not found in closed-canopy forests. Therefore, the combination of savanna and closed-canopy forests results in high ecosystem diversity. In-situ oak seedling bioassays have revealed that oak savannas are spatially heterogeneous in terms of seedling ectomycorrhizal infection, with 64% of root tips infected on seedlings near trees compared with 28% infection distant from trees. Based on transects at forest / field edges, ectomycorrhizal infection of seedlings remains high up to around 16 m from trees and then abruptly declines. We hypothesized that niche partitioning by ectomycorrhizal fungi along a distance gradient from trees would contribute to total fungal diversity; however, very limited evidence of niche partitioning was found. These studies document the extremely high diversity of ectomycorrhizal fungi in oak savannas, and the role of fire in maintaining this diversity.

Do predation and host plant quality interact to regulate soybean aphid?

Date Presented: Saturday Night

Lead Author: Douglas Landis
Co-Authors: Alejandro Costamagna, Kurt Thelen, Christina DiFonzo, Matthew O’Neal
Institutional Affiliations: Michigan State University
Primary Site: KBS

Abstract: The soybean aphid (Aphis glycines Matsumura) is an invasive species from Asia that has become a major pest of soybean in the US since its discovery in 2000. Prior research has shown that existing natural enemy communities contribute to A. glycines population regulation in Michigan soybeans and can result in effective economic control. The differential disturbance gradients represented on the KBS LTER site are likely to influence A. glycines population regulation via two mechanisms. First, 14 years of differential management on the KBS LTER site have created differences in generalist natural enemy assemblages that may regulate the ability of this invasive herbivore to successfully colonize these habitats via top-down influences. Second, by altering soil and nutrient conditions, treatment regimes may alter host plant phenology and nutritional quality through bottom–up effects that may influence A. glycines intrinsic rate of increase. We present results from 2003 studies on the KBS LTER site that test three hypotheses: 1. Generalist predator communities do not differ among selected LTER treatments. 2. A. glycines establishment and population growth does not differ among the selected treatments. 3. There is no direct or interactive effect of predator community and agronomic practice on A. glycines population regulation in the selected treatments. These studies provide a view of the ecological factors regulating A. glycines populations under a variety of relevant agronomic conditions in Michigan and provide information on practical management options.

Does DOM Have a Role in Promoting Cyanobacterial Blooms in Florida Bay, USA?

Date Presented: Friday Night

Lead Author: Patrick J. Gibson
Co-Authors: Susan K. Dailey, Joseph N. Boyer
Institutional Affiliations: Southeast Environmental Research Center, Florida International University
Primary Site: FCE

Abstract: The clear, shallow, oligotrophic waters of Florida Bay are characterized by typically low phytoplankton biomass, yet periodic cyanobacteria blooms occur. We hypothesized that allochthonous DOM was providing a subsidy to the system in the form of organic nutrients. We incubated water from four bay sites under natural light conditions with either DOM (>1 kD) or inorganic nutrient (N+P) enrichments. These samples were analyzed for bacterial numbers (DAPI epifluorescent microscopy), bacterial production (3H-thymidine uptake), phytoplankton production (PAM fluorometry), CHLA, nutrients, and alkaline phosphatase (AP) activity. Inorganic nutrient additions resulted in an ephemeral bloom characterized initially as cyanobacterial and brown algal guilds but changed to green and/or brown guilds by day 6. DOM influence on overall phytoplankton concentrations was slow and relatively little, but it yielded a different community structure by the end of the experiment. Because of sustained AP activity, the DIN:TP ratio decreased 10 fold in the N+P treatments as the system progressed towards N limitation. This ratio did not significantly change for DOM treatments. It is possible that the composition of nutrient inputs is a key factor in bloom initiation but that the alleviation of N and P limitation by enzymatic activity on the DOM pool facilitates their persistence.

Does legacy C fuel soil food webs in the Antarctic Dry Valleys?

Date Presented: Saturday Night

Lead Author: J.E. Barrett
Co-Authors: Ross Virginia, Diana Wall and Andy Parsons
Institutional Affiliations: Dartmouth College, Colorado State University
Primary Site: MCM

Abstract: The Antarctic Dry Valleys are among the most extreme soil environments on Earth, supporting simple food webs subsisting on trace concentrations of soil organic matter (SOM) largely derived from legacies of paleo-lake sediments deposited during the Last Glacial Maximum (LGM). For example, C and N isotope ratios show that SOM is comprised of mixed sources including both ancient and contemporary material, but it is unknown which sources are most important to contemporary food webs. Long term studies indicate that soil biota are limited by C, though sources of organic matter are not obvious. Here we present a synthesis describing dry valley SOM based upon in situ C mineralization, laboratory rate kinetics distinguishing among rapidly cycling and inactive pools, and invertebrate C assimilation rates. Rates of C mineralization are among the lowest reported for terrestrial soils, yet residence times for C are surprisingly short considering that this ecosystem is strongly influenced by legacies carried over from the LGM. Tracer (13C) assimilation suggests that energy flow through nematodes wields a disproportionate influence on C cycling considering their small biomass. However, it is likely that soil metabolism is limited to brief periods of favorable conditions following melt events. Organic matter is well characterized from kinetic studies using a 2 pool model with rapid (

Dust emission at the Jornada Basin LTER

Date Presented: Friday Night

Lead Author: Dale Gillette
Primary Site: JRN

Abstract: Our objective was to determine if vegetation type affects the emission of dust from the Jornada LTER. Two findings guided our way: (1) that sandy soils possess the lowest threshold wind velocities and are the largest contributors to dust emissions at the Jornada; and (2) that horizontal sand fluxes are excellent proxies for vertical fluxes of PM10 dust (i.e., emissions of fine dust). We monitored horizontal sand fluxes at 15 sites representing the five major vegetation types at the JRN (black grama grasslands, playa grasslands, tarbush shrublands, creosotebush shrublands, and mesquite shrublands) along with a sandy site that had been stripped of all vegetation (the scrape site) for comparison. We found that: (1) land dominated by mesquite is the most important area for active sand movement at the Jornada LTER; and (2) the most active sand movement in the mesquite-dominated ecosystems takes place on elongated bare soil patches ( “streets”) having sandy-textured soil with the mesquite plants oriented in the direction of the strongest winds. To integrate the wind observations, vegetation mapping, and sand flux monitoring, we modeled the spatial and temporal mean airborne sand mass flux. The model had the form of an expectation integral that used information on the following: the increase in sand flux with street length, a function for the horizontal mass flux based on friction velocity and threshold friction velocity, wind speed probability versus wind direction, probability of street length versus direction, and probability of friction velocity being exceeded. The model calculations of mean sand flux movement showed fairly good proportionality with the observed mean sand fluxes at three sites dominated by mesquite vegetation.

DYNAMIC EVOLUTION OF BARRIER ISLAND MORPHOLOGY AND ECOLOGY FROM 1996 TO 2002 DOCUMENTED USING HIGH-RESOLUTION GPS-GIS TOPOGRAPHIC MAPPING SURVEYS, VIRGINIA COAST RESERVE

Date Presented: Saturday Night

Lead Author: Craig Kochel
Co-Authors: Charles R. Carlson, Philip H. Smith, Byron K. Light
Institutional Affiliations: Bucknell University, University of Virginia
Primary Site: VCR

Abstract: Dramatic topographic and ecological changes have been documented on the barrier islands of the Virginia Coast Reserve between 1996 and 2002. Long-term study sites included in the VCR-LTER (Virginia Coast Reserve - Long Term Ecological Research) site range from the macro-scale encompassing Myrtle Island to meso-scale washover sites on Parramore and Hog Islands. The barrier environments are so dynamic that conventional surveying methods were abandoned in favor of using GPS. Hi-resolution GPS mapping with cm-scale accuracy is an effective method for detailed geomorphic mapping, illustrating the evolution and destruction of dunes, washover flats, and beach environments. Importing field GPS data into ArcView GIS permits aerial and volumetric calculations to be made of changes within elevational slices of the islands between surveys. During the past 7 years, Myrtle Island has been transformed from a high-profile barrier with dunes over 5 m above MSL (most of the island was between 2-3 m above MSL) to a washover flat with most of the island less than 1 m above MSL. Since 1996, the subaerial extent of Myrtle Island has gone from 268,895 m2 to 48,787 m2 (less than 18% of the surface area in 1996). This represents a total net volume loss of 329,359 m3 of sand, leaving Myrtle with only 8% of the subaerial volume it had in 1996. The majority of these changes have occurred in the absence of major coastal storms, probably influenced by alterations in the longshore drift related to the dynamics of Ship Shoal Inlet and the effects of moderate extratropical storms. More than 400 m of westward retreat of the shoreline has occurred since 1996, averaging about 80 m/yr. Wholesale subaerial island ecologies have been lost as the dunes which hosted freshwater woody vegetation have eroded. These sites illustrate the remarkable spatial variation in the geomorphic response of barrier islands on the Virginia coast, even when major storms have been absent.

Dynamics of Evapotranspiration in Semiarid Grassland and Shrubland during the Summer Monsoon Season, central NM

Date Presented: Saturday Night

Lead Author: Shirley Kurc
Co-Authors: Eric Small
Institutional Affiliations: University of Colorado
Primary Site: SEV

Abstract: In an effort to understand the coupled water-energy cycle in semiarid environments, we measure temporal fluctuations of evapotranspiration (ET) and identify factors that control these fluctuations. Flux measurements are made using the Bowen ratio method, accompanied by measurements of soil moisture and radiation. We present three summers of data from both a grassland site and a shrubland site, situated within 2 km of each other within the Sevilleta National Wildlife Refuge of central NM. Midday available energy (i.e. Qa = Rn - G) is higher at the grassland than at the shrubland by about 20 % (i.e. 80 Wm-2). At both sites, evaporative fraction (i.e. EF, the fraction of available energy used toward latent heating) is strongly correlated with surface soil moisture (0-5cm). However, the sensitivity of EF to surface soil moisture is about 30 % lower at the grassland site than at the shrubland site. The differences in Qa and EF between grassland and shrubland are equal in magnitude but opposite in sign, yielding (1) remarkably similar time series of ET at the two sites and (2) an identical relationship between ET and soil moisture at the two sites. From the results of our study, we believe that the observed differences are the result of how ET is partitioned into evaporation (E) and transpiration (T) at the two sites, with greater E at shrubland due to more bare soil at that location. In an effort to partition ET into its respective components, measurements of E and T at the grassland and shrubland following precipitation events were made during summer 2003. We expect to present preliminary results from these efforts as well.

Earthworms, soils and N-cycling in remnant forest patches in the Baltimore Metropolitan Area

Date Presented: Friday Night

Lead Author: Katalin Szlavecz
Co-Authors: Sarah Placella, Richard Pouyat, Vincent Giorgio, Peter Groffman, and Csaba Csuzdi
Institutional Affiliations: The Johns Hopkins University, USDA Forest Service, SUNY Syracuse, Institute for Ecosystem Studies and the Hungarian Museum of Natural History
Primary Site: BES

Abstract: We report earthworm and soil data for fieldwork conducted between 2001-2003. The objective of our study was to characterize and compare urban, suburban and rural soils, litter and earthworm communities in the Baltimore Metropolitan Area. We hypothesized that soil properties and earthworm abundances would vary between urban and rural forest sites and that chemical properties would show greater variation than physical properties. Fifteen forested sites were selected and classified as urban, suburban, or rural based on geographic and demographic features in the surrounding area. Soil samples were taken for bulk density, pH, and organic matter content as well as elemental analysis. For all samples, pH ranged from 3.67 to 5.71. Bulk density ranged from 0.69 /cm³ to 1.58 g/cm³ with an average of 1.10 g/cm³ while organic matter content ranged from 4.1% to 17.2% with an average of 8.6%. Significant differences (p<0.05) between urban/rural sites were found for bulk density, soil Ca, Mg, and Na (with urban sites showing higher values than rural for each). In urban soils potential N-mineralization rates and potential nitrification rates were 3.6 and 13.5 times greater, respectively, than in rural soils. Earthworm density and biomass varied between 5 and 288 ind m^-2 and 5 and 144 g m^-2, respectively. Urban forests had higher abundance than rural forests. Earthworm biomass showed positive correlation with pH, and negative correlation with soil organic matter content. The earthworm fauna is dominated by non-native species. In general, urban and rural forests formed two distinct categories, indicating that environmental changes resulting from urbanization and habitat fragmentation affect soil community and nutrient cycling. However, given the variation in parent material and soil type of the area, evaluation of site differences should consider both natural (geology) processes and anthropogenic impact (land use change).

Ecological interpretation and assessment of ecosystems using environmental acoustic data and analysis

Date Presented: Saturday Night

Lead Author: Stuart Gage
Co-Authors: Brian Napoletano
Institutional Affiliations: KBS LTER, Michigan State University
Primary Site: KBS

Abstract: The ability to hear and to interpret sound is one of our basic senses. Sounds produced by the environment are an untapped resource to enable humans to assess the health of the ecosystems within which they live or extract resources. The arrays of sounds in a place depend on the habitat type, the mosaic of habitats in the landscape, the time of day, and the season of the year. We have hypothesize that sounds also reflect the status of the ecosystems. Many groups of animals produce sound and use acoustic signals to communicate. Patterns of acoustic signals reflect the dynamics of biological, social, and physical systems in the landscape. Changes in the spatial and temporal distribution of acoustic signal patterns reflect changes in those dynamics. The exact meaning of these signals, in terms of the processes and interactions they represent between social and bio-physical systems is a challenging area of study. A framework for the study and understanding of patch-level acoustic signals from a landscape is presented. This framework includes a) the definition of a soundscape, b) a taxonomy of the biological and physical characteristics of a soundscape, c) an analytical approach to quantify the components of an acoustic sample taken from the environment, d) a protocol for measurement of acoustic signals in the environment, e) a cyber-infrastructure necessary to manage numerous acoustic signals sampled from different environments, and f) a web tool to present acoustic information in near-real time from different places at different times. Our research has produced methods to characterize acoustics in human dominated ecosystems. Our findings are in three areas: soundscape classification; measurement of diurnal patterns of acoustics, and the development of indices relating human and biophysical acoustics. We present case studies to demonstrate the framework and outcomes of some monitoring and measurements of environmental acoustics.

Ecology of Native and Exotic Urban Populations of Eastern Gray Squirrels

Date Presented: Friday Night

Lead Author: Tommy Parker
Co-Authors: Charles Nilon
Institutional Affiliations: University of Missouri
Primary Site: BES

Abstract: The eastern gray squirrel (Sciurus carolinensis) is one of the many species of tree squirrels found in North America. This species was introduced at 30 locations throughout Great Britain from 1876 to 1929. Resulting from the urbanization of the species, gray squirrels are abundant in urban areas in both North America (native) and the United Kingdom (exotic). Manski et al., (1980) developed hypotheses on the effects of urbanization of wildlife species. Because of human activity, urban areas are more susceptible to introductions of exotic fauna; however, there have been no investigations on the efficacy of these hypotheses on exotic species in urban areas. Therefore, six study sites will be established in both metropolitan areas of Baltimore, Maryland and London, England. Comparisons of population densities, intraspecific aggression, wariness, and activity patterns of native and exotic urban populations of gray squirrels will be done to test hypotheses on the effects of urbanization on wildlife species.

Ecosystem change in Czech Republic after a decrease in emissions

Date Presented: Friday Night

Lead Author: Viera Straskrabova
Primary Site: INT

Abstract: In Czech Republic (like in the surrounding "post-communist" countries: Slovakia, Poland, former East Germany) a drastic decrease of emissions occurred during 1980 - 2000, mostly due to political and economical changes connected with the change of political regime. Emissions of nitrogen and sulphur compounds, both from industrial emissions and from fertilizers, dropped severely. A recovery of previously acidified lakes and forests is followed and some changes shown. In aquatic ecosystems a significant recovery was observed in acidified lakes located on crystalline bedrock - changes in pH and chemistry, and also a reappearance of previously extinct zooplankton species. A delay of ecosystem recovery due to slow soil processes in the catchment is documented. In damaged forest ecosystems not any significant change was observed in the forest itself, but lichens and especially mycorrhizal fungi species composition has been changed and indicated a recovery. In lowland aquatic ecosystems, only insignificant changes in aquatic chemistry and no changes in biota due to emissions decrease were observed. The evaluation is complicated by other changes occurring simultaneously like eutrophication and changes in land-use. Some examples of eutrophication phenomena in fish-ponds and subsequent effect on birds (at Ramsar sites) are shown.

Ecosystem Drivers of Rodent-borne Disease Outbreaks: New studies at the Sevilleta LTER Site.

Date Presented: Saturday Night

Lead Author: Robert Parmenter
Co-Authors: Terry L. Yates, Nitant Kenkre, Gregory Glass, James Mills, Darrin Carrol, Kenneth Gage, and Michael Kosoy.
Institutional Affiliations: University of New Mexico; Johns Hopkins University; CDC (Fort Collins and Atlanta)
Primary Site: SEV

Abstract: The Sevilleta LTER group has begun a new study funded by NSF/NIH to examine the role of climate dynamics in initiating rodent-borne disease outbreaks. Climate variability is thought to affect a number of rodent-borne zoonotic diseases such as plague, vector-borne zoonotic bartonellosis and hantaviral diseases. The Trophic Cascade Hypothesis (TCH) was developed to explain changing levels of human risk for zoonotic diseases associated with climate variability in the U.S. Southwest. This new project will evaluate the causal pathways of the TCH and subsequent dispersal of rodents by studies of climatic variability, ecosystem responses to climate variation, rodent population dynamics and movements, and the dynamics of three pathogens (hantavirus, plague, and bartonellae) in New Mexico. Field studies will allow the parameterization of mathematical models for both viral and bacterial disease transmission. These models will serve as prototypes for more generalizable predictive models that may be applied to rodent-borne diseases in other ecosystems throughout the world.

Ecosystem management along a rainfall gradient

Date Presented: Friday Night

Lead Author: Yehoshua Shkedy
Co-Authors: M. Waltzac1, Z. Kuller1, I. Shifman1, A. Perevolotsky2, M. Shachak3
Institutional Affiliations: 1Israel Nature and Parks Authority, 2The Agricultural Research Organization –Volcani Center
Primary Site: INT

Abstract: Two processes induce a decrease in species diversity along a rainfall gradient in Israel. In the northern, Mediterranean zone of Israel (mean annual precipitation >400 mm), woody vegetation is expanding as a result of natural successional processes, reduced grazing and clear cutting. Consequently, herbaceous vegetation diversity is declining. In the southern arid zone (mean annual precipitation <400 mm), high grazing pressure and soil erosion reduce herbaceous vegetation diversity. The network of LTER sites along a rainfall gradient in Israel, is devoted to research, management and education. The sites and their management objectives are: Hanadiv: Located in the Mediterranean zone with 600 mm of rain. This site deals with park management for biodiversity conservation, public use and education. Jerusalem: A site near Jerusalem with 600 mm of rain. This site focuses on park management for recreation, in a landscape mosaic of a Mediterranean woodland and planted pine forest. Judea: Located in the dry mediterranean zone with 450 mm of rain. This site focuses on nature reserve management of a maquis, using small-scale trees and shrub removal (clear cutting) and grazing. Lehavim: Located in the semi-arid zone, with 300 mm of rain. This site focuses on management for sustainable grazing by indigenous people (Bedouin). Shaked: Located in the semi-arid zone with 250 mm of rain. This site focuses on afforestation under semi-arid conditions, for recreation and soil conservation. Avdat: Located in the arid zone with 100 mm of rain. This site focuses on runoff harvesting for agriculture, nature conservation and recreation. Ramon: Located in the extreme arid zone with mean annual precipitation <100 mm. This site focuses on nature conservation in arid environments, and tourism. The management goal of the network is to synthesize knowledge that will generate recommendations for decision makers, land managers and planners on the local, regional and national scales.

Ecosystem Response to 15 years of Chronic Nitrogen Additions at the Harvard Forest LTER,

Date Presented: Friday Night

Lead Author: Alison Magill
Co-Authors: John Aber, William Currie, Knute Nadelhoffer
Institutional Affiliations: University of New Hampshire, University of Michigan
Primary Site: HFR

Abstract: The nitrogen saturation potential of temperate forests in the Northeastern United States and in Europe is of mounting concern as nitrogen deposition from anthropogenic sources continues to increase. In order to determine the long-term impact of N inputs, fertilizer addition plots were established at the Harvard Forest LTER Site. Two forest stands, a red pine plantation and a mixed hardwood stand, have been receiving NH₄NO₃additions at 0 (control), 5 (low N; low N+S) and 15 (high N) g N m^-2 yr^-1since 1988. Key indicators of nitrogen saturation have been measured over 15 years, including soil chemistry, soil solution chemistry, foliar chemistry and forest productivity. The hardwood stand has consistently shown a slower response to N additions for nearly all parameters measured. Soil solution inorganic nitrogen concentrations have remained elevated in both the pine high N and hardwood high N plots. Soil N storage calculations revealed that approximately 15% of N is stored in the organic horizon leaving an estimated 55% of retained N in the mineral horizons. N content in Oak foliage has responded moderately to N additions ranging from 10% (low N and low N+S plots) to 25% above controls in the high N plot. Red pine foliage response has been large with low N and low N+S foliage approximately 50% greater than controls; high N foliage has doubled from control values. Tree health has declined severely in both high N plots with tree death (by stem) reaching 55% in the pine high N stand and 49% in the hardwood high N by 2002. Total litterfall mass has not declined significantly although contribution of understory species has increased with dominant species death. Continued long-term measurements will include an analysis of plot recovery and changes in community structure with pine removal.

Ecosystem-Level Processes in Everglades Marsh Periphyton Assemblages

Date Presented: Friday Night

Lead Author: David Iwaniec
Co-Authors: Daniel Childers
Institutional Affiliations: Florida Internation University, FCE-LTER
Primary Site: FCE

Abstract: Periphyton assemblages are an important component, indicator of change, and gauge of the state of aquatic ecosystems. We are investigating the effects of landscape location and water source on periphyton dynamics in the oligotrophic Southern Everglades. Our study sites are along transects anchored at canal inflows and extend through the sawgrass dominated marsh to the mangrove wetlands. Patterns and magnitudes of periphyton dynamics display significant landscape location and water source effects. Critical to understanding how landscape location and water source affect periphyton dynamics is an understanding of how regulatory mechanisms control structural and functional dynamics of periphyton.

Effect of developed land use and wetlands on hydrologic DON losses from the Ipswich River watershed, MA

Date Presented: Saturday Night

Lead Author: Brian Pellerin
Co-Authors: Wil Wollheim, Charles Hopkinson, William McDowell, Michael Williams, Charles Vorosmarty, Michelle Daley
Institutional Affiliations: UNH, UNH, MBL, UNH, MBL, UNH, UNH
Primary Site: PIE

Abstract: Recent studies in old-growth forests suggest that land cover change and chronic nitrogen (N) deposition in the temperate northeastern U.S. may shift the dominant form of N in watershed fluxes from dissolved organic N (DON) to dissolved inorganic N (DIN), with potential effects on aquatic ecosystem structure and function. However, our understanding of processes controlling DON concentrations in drainage waters and the role of DON in ecosystem N budgets remains limited. Here we present data from 39 watersheds in northeastern Massachusetts (PIE-LTER) that encompass a gradient of developed land use (0-90 % urban plus agriculture) and wetland abundance (0-32 %) to assess controls on mean annual DON concentrations and DON / TDN in drainage waters. In addition, we compiled previously published data from 114 northeastern U.S. watersheds to evaluate broader-scale DON relationships with developed land use and wetlands. Our results show that the percentage of wetlands explains 57 % of the variability in DON concentrations in our study watersheds and 61 % when all literature data are included. Excluding watersheds with direct wastewater inputs to surface waters improves the regional relationship significantly (r2 = 0.81). The percentage of developed land use is a relatively poor predictor of DON concentrations for both the Ipswich (r2 = 0.11) and our compiled dataset (r2 = 0.27). Developed land use percentage explains 52 % of the variability in DIN concentrations in the Ipswich River watersheds, but only 34 % in the compiled dataset. The ratio of DON / TDN is best explained by a multiple regression of wetland percentage and developed land use percentage for both the Ipswich (r2 = 0.71) and the compiled dataset (r2 = 0.48). Our results indicate that watersheds with abundant wetlands may have high DON concentrations and DON / TDN ratios despite elevated anthropogenic N inputs via deposition and human activity.

Effects of agricultural disturbance on organic matter dynamics in southern Appalachian streams

Date Presented: Friday Night

Lead Author: Elizabeth M. Hagen
Co-Authors: Jackson R. Webster
Institutional Affiliations: Virginia Polytechnic Institute and State University
Primary Site: CWT

Abstract: Streams and terrestrial ecosystems are linked through shading and allochthonous organic matter inputs from streamside vegetation. Reduction of allochthonous input, primarily in the form of leaf litter, may affect stream ecosystem structure and function. Agricultural land use often reduces the amount of riparian vegetation. The purpose of this study was to assess the impact of agricultural land use on organic matter dynamics in southern Appalachian streams (North Carolina and Georgia). We measured allochthonous input, leaf breakdown rate, percent canopy cover, water quality, macroinvertebrate diversity and richness, algal biomass, and chlorophyll a in twelve streams with differing degrees of land use: forest and light, moderate, and heavy agriculture. Additionally, we measured the density, size, and distribution of large woody riparian vegetation to examine linkages between the riparian tree community and composition of the leaf litter input entering the stream ecosystem. Leaf litter input make up 62% of total allochthonous input to heavy agricultural streams, and 82 - 89% of total input to forested, light agricultural, and moderate agricultural streams. Our results indicate that disturbances by agricultural land use can have significant impacts on stream organic matter dynamics.

Effects of Black-tailed Prairie Dogs on Plant Community Structure and Species Composition on the Shortgrass Steppe

Date Presented: Saturday Night

Lead Author: Laurel Hartley
Co-Authors: James K. Detling
Institutional Affiliations: Department of Biology, Colorado State University
Primary Site: SGS

Abstract: Prairie dogs (Cynomys ludovicianus) can have profound impacts on plant communities of grasslands. In mixed-grass prairies, their grazing reduces canopy height, litter, standing biomass, and grass:forb ratios. Studies from the mixed-grass prairie are used to make management decisions in all types of grasslands. However, the effects of prairie dogs in the shortgrass steppe may be different from their effects in the mixed-grass prairie. The SGS is drier and is dominated by drought resistant species such as blue grama (Bouteloua gracilis) that are also resistant to grazing. Further, colonies on the SGS are subject to periodic extinction and recolonization due to plague, which may serve to temporarily alleviate grazing pressure from prairie dogs. Since 1997, we have monitored plant community composition, species richness, and biomass on 5 prairie dog towns and 5 uncolonized sites at the SGS-LTER. Our data include years prior to, during, and after a plague outbreak. Biomass of blue grama was about 30% lower on prairie dog colonies than at off colony sites. Similarly, total grass biomass on active colonies was consistently lower than off colonies. By contrast, forb biomass on active colonies averaged nearly three times more than off the colonies. While these trends are in the same directions as those observed in mixed grass prairie, the magnitude of the differences between on and off colony sites were considerably less in the shortgrass steppe. This is further evidence that the SGS is highly adapted to grazing. Early in 1999, prairie dogs in two of the colonies died off from plague. By August,1999, graminoid biomass on the extinct colonies had increased to values that were essentially identical to those off the colonies, and forb biomass on extinct towns had decreased to values similar to those off the colonies. Thus, it appears that the effects of prairie dogs on plant biomass are reversed quickly following loss of prairie dogs at our SGS site.

Effects of cropping system diversity on weed communities in a row-crop diversity experiment at the KBS LTER

Date Presented: Saturday Night

Lead Author: Richard Smith
Co-Authors: Katherine L. Gross
Institutional Affiliations: Michigan State University
Primary Site: KBS

Abstract: A number of recent experimental studies in grasslands have shown that plant diversity can have important effects on a number of community and ecosystem processes. We have recently established an experiment at the KBS LTER in which cropping system diversity is manipulated by varying the number of crops in a row-crop rotation and the use of cover crops. The twenty experimental treatments in the “Biodiversity Plots Experiment” were established in 2000 and span a realistic range of crop diversities including no-crop fallows (spring and fall-tilled), single species monocultures (continuous corn, soybean, and winter wheat), two-crop (corn-soybean, wheat-soybean) and three-crop rotations (corn-soybean-wheat), with and without cover crops. All treatments are managed without chemical inputs. We have been monitoring the effects of cropping system diversity on the associate weed communities by sampling the soil seed bank (early May, just after spring crops are planted) and emergent weed community (biomass harvest in late August). Interestingly, cropping system diversity (e.g. the number of crops in the rotation or use of cover crops) had little effect on weed seed densities, emergent weed biomass, species richness, or species evenness. Multivariate analysis of emergent weed community composition among treatments revealed that weed communities in fall fallows and winter wheat treatments are distinct from those in spring-sown crops and fallows. These results suggest that initial differences in weed community composition associated with cropping system diversity are driven by differences in tillage time (fall vs. spring) and that the timing of management activities is initially a more important factor than rotational diversity in determining weed community composition and structure in row-crop systems.

Effects of food web structure and landscape age on zooplankton and fish assemblages in lakes at the Toolik Lake LTER station.

Date Presented: Friday Night

Lead Author: Chris Luecke
Co-Authors: Greta Burkart
Institutional Affiliations: Utah State University
Primary Site: ARC

Abstract: The zooplankton and fish assemblages in four lakes of recent glacial origin (approximately 12,000 YBP) were compared to assemblages in four older lakes (30,000 – 70,000 YBP). Two lakes in each set contained fish and two lakes in each set were fishless. Marked differences in zooplankton species composition, abundance and production were apparent in the lakes of differing food web structure. Fishless lakes supported four times the biomass and production of zooplankton compared to lakes with fish. Daphnia dominated biomass and production of fishless lakes, whereas Diaptomus dominated zooplankton assemblages in lakes with fish. Lakes on older landscape surfaces contained whitefish and arctic char whereas lakes on younger surfaces were dominated by arctic grayling and lake trout. Differences in zooplankton assemblages in young versus older lakes were small compared to differences due to the presence of planktivorous fish.

Effects of habitat heterogeneity at multiple spatial scales on the distribution and abundance of a stream salamander

Date Presented: Friday Night

Lead Author: Winsor Lowe
Co-Authors: Gene E. Likens
Institutional Affiliations: Institute of Ecosystem Studies, PO Box AB, Millbrook, NY 12545
Primary Site: HBR

Abstract: We investigated how physical and biological heterogeneity at multiple scales of habitat organization affected the distribution and abundance of the headwater stream salamander Gyrinophilus porphyriticus (Plethodontidae), a species occurring throughout the Hubbard Brook drainage. At the reach scale, salamander larvae and adults displayed differential associations with physical habitat conditions. Both larvae and adults were positively associated with riffles, characterized by moderate gradient and medium-sized substrate, but while larvae were negatively associated with cascades, characterized by high gradient and large substrate, adults were negatively associated with runs, characterized by low gradient and small substrate. Adults had no effect on the survival or growth of larvae in experimental mesocosms, suggesting that these reach-scale habitat associations were not a function of intraspecific interactions. Combining reaches into two contiguous 500 m-long sections comprising an entire 1st-order stream, low habitat quality and reproduction in the upstream section made population stability there dependent on immigration from the downstream section. In entire 1st-order streams throughout New Hampshire, abundance of G. porphyriticus larvae was negatively related to brook trout abundance, while adult abundance was negatively related to logging-associated sedimentation. Total G. porphyriticus abundance was lower in “isolated” streams, those flowing directly into higher-order rivers, than in “paired” streams, those joining other 1st-order streams and thereby providing population connectivity. These results underscore the value of comprehensively incorporating the hierarchical organization of stream habitat in investigations of controls on species distribution and abundance.

EFFECTS OF HARVEST AND ROADS ON IN-STREAM WOODY MATERIAL IN BLUE RIVER BASIN, CASCADE RANGE, OREGON

Date Presented: Friday Night

Lead Author: Nicole M. Czarnomski
Co-Authors: David M. Dreher, Julia A. Jones, Frederick J. Swanson
Institutional Affiliations: Department of Forest Science, Oregon State University, Corvallis, Oregon , Department of Geosciences, Oregon State University, Corvallis, Oregon, USDA Forest Service, Pacific Northwest Research Station, Corvallis, Oregon
Primary Site: AND

Abstract: Despite many studies of large wood in streams, few landscape-scale studies have been conducted, and yet the history of forest harvest and road building might be expected to have left a signal on wood patterns in streams. This study examined this question at large (>50 km2) spatial and long (>25 year) temporal scales, based on longitudinal surveys of 25.2 km of stream length in five sub-basins of the Blue River Basin, Cascade Range, Oregon. Six sites, ranging from 1.6 km to 14.1 km in length, were surveyed along 2nd to 5th-order channels on public forest land. Wood volumes, numbers of pieces of large wood, numbers of accumulations and timing of emplacement were determined in the surveys. Survey data were matched with spatial data on harvest and road building practices using GIS. Study streams have undergone distributed patch clearcutting and road construction concentrated during the 1950s and 1960s. The proportions of surveyed stream lengths with harvest and road activities within 40 m was 66% (Cook Creek), 55% (Mack Creek), 53% (Lower Lookout), 37% (McRae Creek and Upper Lookout), and 7% (Quentin Creek). For all study locations combined, 50m channel segments when there is no harvest or road influence had an average of 356 m3/ha, whereas harvested and roaded areas had from 80 to 157 m3/ha (Bonferroni adjusted p<0.03). Approximately 80% of the wood volume occurred in accumulations. The 5th-order channel (Lower Lookout) had significantly lower wood volumes (109 m3/ha) than all other locations (200-378 m3/ha, Bonferroni adjusted p < 0.05) and significantly lower numbers of large pieces (23 large pieces/ha) compared to all other locations (39 vs. 64 large pieces/ha) (Bonferroni adjusted p<0.008). Thus, the legacy of harvest and road activities conducted in the 1950s and 1960s was still apparent in in-stream wood patterns nearly 40 years later.

Effects of litter stoichiometry and soil nutrient availability on decomposition in Oak savanna at the Cedar Creek LTER

Date Presented: Friday Night

Lead Author: Daniel L. Hernandez
Co-Authors: Sarah E. Hobbie
Institutional Affiliations: University of Minnesota
Primary Site: CDR

Abstract: This study utilized a natural gradient in soil nitrogen (N) availability and litter N content developed as a result of a fire frequency manipulation to investigate the relative influence of substrate and soil nutrient availability on the decomposition of oak (Quercus ellipsoidalis) litter at the Cedar Creek LTER in central Minnesota. Manipulation of fire frequency at these sites over the last 40 years has resulted in a gradient in vegetation structure ranging from closed canopy oak woodland in unburned sites to oak savanna in frequently burned sites. Increased fire frequency is also associated with a decrease in litter N concentrations and soil N availability. Oak litter with a range in initial N concentrations was collected from the sites and placed in litterbags across the soil nutrient gradient. We deployed a second set of litterbags that receive treatments of fungicide, bactericide, or both to examine the effects of possible microbial interactions in decomposition. After 7 months, we measured mass loss, litter carbon (C), N, and phosphorous content, and litter microbial biomass. Soil nutrient availability was measured using ion exchange resin bags throughout the growing season. Initial analyses of this two-year experiment indicate that both litter stoichiometry and soil nutrient availability may affect rates of decomposition. For untreated litterbags, high N litter decomposed significantly faster than low N litter. Site nutrient availability was also positively correlated with rates of decomposition, and N immobilization was higher in sites with high soil N availability. Application of fungicide (but not bactericide) significantly slowed both decomposition and N immobilization, suggesting that rates of decomposition of oak litter at these sites is highly dependent on the immobilization of N by the fungal community.

Effects of physical disturbance on food-web structure in two Arctic streams, North Slope, Alaska

Date Presented: Friday Night

Lead Author: Stephanie Parker
Co-Authors: Alex Huryn
Institutional Affiliations: University of Alabama
Primary Site: ARC

Abstract: Streams in arctic Alaska may be differentiated by geomorphology, chemistry, water sources, and disturbance regime. Two stream types, a groundwater spring and a mountain stream, drain adjacent headwater catchments of the Ivishak River on the North Slope. The groundwater spring maintains a relatively constant temperature and discharge throughout the year, whereas the mountain stream is highly dependent on seasonal patterns of precipitation and air temperature. Measurements of bed disturbance using marked rock movement and estimates of tractive force and particle size distribution suggest that the mountain stream has a more intense disturbance regime than the groundwater spring. Macroinvertebrate community structure shows dramatic differences in trophic structure between streams, although taxonomic richness was similar (22-24 taxa). Biomass in the spring stream (6,466±1401 mg DM m^-2; X±SE) was an order of magnitude greater than the mountain stream (733±274 mg DM m^-2). Furthermore, predators account for 40% of macroinvertebrate biomass in the spring stream, but only 7% in the mountain stream. This imbalance in predator biomass between the two streams has implications for the relative roles of biotic and abiotic control of production. Contrasts in disturbance regime among arctic streams are presumably a major determinant of differences in ecological structure and function.

Effects of sediment resuspension on light availability and implications for primary productivity in Hog Island Bay, Virginia

Date Presented: Saturday Night

Lead Author: Sarah Lawson
Co-Authors: Karen McGlathery, Patricia Wiberg
Institutional Affiliations: University of Virginia
Primary Site: VCR

Abstract: Turbidity is an important physical control on light availability and photosynthesis in shallow coastal lagoons. These lagoons are typically dominated by benthic primary productivity because most of the sediment surface is in the euphotic zone. The shallow depth also makes the sediment susceptible to wave resuspension. Light availability and limitation is often examined through monitoring data, but a mechanistic, process-based approach allows a more comprehensive and dynamic view of the possible extent of light limitation both spatially and temporally. In this study, light attenuation in the water column is described by a linear combination of particulate inorganic matter, particulate organic matter, and chlorophyll a concentrations. Sediment suspension is represented by field and modeling data with tides providing a background pattern of sediment transport overlain by more episodic suspension from wind waves. Combining the light equations and the sediment transport data allows prediction of areas of light limitation of benthic plants. In Hog Island Bay, VA, where seagrass has been locally extinct since the 1930’s, this information can be used to predict the possible areal extent of seagrass recolonization.

Effects of the frequency and duration of tidal inundation on salt marsh macrophytes

Date Presented: Saturday Night

Lead Author: Diana Rodriguez
Co-Authors: James T. Morris, Helen L. Marshall
Institutional Affiliations: University of South Carolina
Primary Site: PIE

Abstract: Sediment accretion at rates equal to or greater than relative sea level rise is paramount to the stability of coastal salt marshes. Research has suggested a link between marsh elevation, tidal inundation frequency, and salt marsh macrophyte productivity. Frequency and duration of inundation, therefore, may affect macrophyte biomass allocation patterns and overall marsh macrophyte productivity. An experiment was designed to investigate how varying the marsh platform in relation to mean sea level would affect macrophyte production, stand dynamics, and biomass allocation patterns of Spartina alterniflora, the dominant macrophyte along the US eastern and gulf coasts. Photosynthesis, pigment analysis, and leaf temperatures were measured concurrently to assess other physiological affects of inundation frequency. This experiment was replicated in micro- (Cocodrie, LA), meso- (North Inlet, SC) and macro-tidal (Plum Island LTER, MA) salt marshes to further determine how tidal variability also influences macrophyte response. We found no significant differences among treatments in macrophyte annual production, but highly significant differences in terms of stand densities, plant morphology, and photosynthetic rates. Our results indicate that frequency of inundation causes a significant variation in stand densities and plant heights. The highest three treatments had dense stands of shorter stems, whilst the lowest three treatments had fewer culms, and taller average stem heights. While macrophyte production may not vary with treatment, these changes in stand densities and macrophyte morphology may have profound effects on the ability of the marsh to accrete allochthonous sediments and maintain pace with sea level rise. Furthermore, as the elevation below mean high tide decreased, there was an increase in the shoot: root ratio, implying that under scenarios of rising sea level, the ability of the marsh to accrete autochthonous material may also be reduced.

Effects of tillage on species richness and composition of soil basidiomycetes in agroecosystems

Date Presented: Saturday Night

Lead Author: Michael Lynch
Co-Authors: R. Greg Thorn
Institutional Affiliations: The University of Western Ontario
Primary Site: KBS

Abstract: A molecular approach was used to analyze the composition of communities of soil basidiomycetes in Kellogg Biological Station LTER agroecosystems that differ in tillage history. This approach combined soil DNA extraction using a FastPrep method modified to increase recovery of fungal DNA, PCR amplification using basidiomycete-specific primers, cloning and RFLP screening of mixed PCR products, and sequencing of unique PCR products. These fungi, primarily responsible for lignocellulose degradation in plant litter, are not easily cultured from soil and as such have been greatly under-represented in surveys of soil fungi. 10 g subsamples from soil cores were washed through sieves of 250 and 53 µm mesh to remove bacteria and most fungal spores. DNA was extracted from washed organics retained on the 53 µm mesh sieve and basidiomycete-specific PCR primers yielding 2.4 kb amplicons that span the nuclear ribosomal ITS region and approximately 1000 bp into both the 18S and 25S genes were used to obtain templates for cloning. 12 randomly selected transformed colonies were subjected to RFLP screening and unique transformants then sequenced and subjected to phylogenetic analysis. Preliminary results show higher rates of amplification from historically tilled (old field succession; 68%) and never tilled sites (83%) compared to conventional tillage (38%). Similarly, the number of species per sample was greater in no till and never tilled or historically tilled regimes than in conventional tillage. Phylogenetic analysis was performed to determine community composition and to evaluate the diversity of species within and between treatments. This molecular approach should facilitate investigations in soil fungal diversity by avoiding issues surrounding traditional culture methods and provide insight to the community structure of soil basidiomycetes, and their sensitivity to disturbance by tillage.

Effects of urban land cover modifications in a mesoscale meteorological model on surface energetics for the Phoenix metropolitan area

Date Presented: Friday Night

Lead Author: Susanne Grossman-Clarke
Co-Authors: Joseph A. Zehnder, William L. Stefanov
Institutional Affiliations: Arizona State University
Primary Site: CAP

Abstract: A new land cover classification for the Phoenix metropolitan area (Arizona, USA) was used in the fifth-generation PSU/NCAR mesoscale meteorological model MM5. Phoenix is surrounded by natural desert and irrigated agricultural land with a well-defined urban boundary, leading to a sudden change of surface characteristics. The single urban category in the existing 25-category United States Geological Survey (USGS) land cover classification used in MM5 was divided into three classes: built-up urban, suburban mesic residential and suburban xeric residential. This allowed us to consider the influence of urban vegetation and irrigation practices in the surface energy budget and hence the evolution of the boundary layer. 30 meter land cover data were derived from LANDSAT Thematic Mapper (TM) satellite images. Ground truth information was used to determine the composition of mesic and xeric residential areas in terms of typical fractions of irrigated and total vegetation, soil surfaces, roofs and paved surfaces. The data were upscaled to a 30-second grid and used to augment and correct the existing USGS land cover scheme in MM5. A 72-hour simulation starting on may 28th 2001 at 00:00 UTC was performed with MM5 on a 2 km x 2 km grid. The results of this study show that the new land use data have a significant effect on the simulated surface temperatures, latent and sensible heat fluxes and hence the evolution of the planetary boundary layer. This has implications for the simulation of meteorological variables and air quality on a neighborhood scale as well has model based studies of the urban heat island.

Effects of urban land cover modifications in a mesoscale meteorological model on surface energetics for the Phoenix metropolitan area

Date Presented: Friday Night

Lead Author: Susanne Grossman-Clarke
Co-Authors: Joseph A. Zehnder, William L. Stefanov
Institutional Affiliations: Arizona State University
Primary Site: CAP

Enumeration of Forest Soil Methane Oxidizing Communities by Fluorescent In Situ Hybridization

Date Presented: Friday Night

Lead Author: Mark A. Bremer
Co-Authors: Andria M. Costello
Institutional Affiliations: Syracuse University
Primary Site: HBR

Abstract: Anthropogenic acid deposition remains elevated in regions of the Northeastern U.S. Soil acidification due to acid deposition has been shown to decrease soil acid neutralizing capacity (ANC) and affect microbial community structure, function, and diversity. The methane oxidation process is sensitive to pH and methanotroph activity may make forest soils an important natural sink of methane. In situ hybridization with rRNA-targeted, fluorescently labeled oligonucleotide probes was used with confocal scanning laser microscopy to detect and enumerate methanotrophic bacteria in forest soils affected by varying amounts of atmospheric acid deposition. Methanotroph abundance in acidic forest soil communities was lowest in the forest floor and increased with depth. Type I methantroph abundance increases linearly with pH (R^2=0.9929). At Hubbard Brook Experimental Forest, NH, type I cells averaged 1.74+/-0.47 x 10^7 cells gram^-1 wet soil and type II methanotrophs averaged 1.85+/-0.67 x 10^7 cells gram^-1 wet soil, representing <0.1% of acridine orange direct cell counts. Sites with higher acid deposition did not show lower numbers of methane oxidizers, suggesting the presence of acid tolerant species.

Environmental Cyber-Infrastructure Needs for Distributed Sensor Networks

Date Presented: Saturday Night

Lead Author: Michener, W.K
Co-Authors: Estrin, D., Bonito, G.M.
Institutional Affiliations: University of New Mexico; University of California, Los Angeles; Duke University
Primary Site: NET

Abstract: The widespread proliferation of the Internet and other communication technologies, especially wireless and acoustic transmission from remote sensors, coupled with the decreasing cost, size, and weight of a variety of sensors is resulting in a major paradigm shift in both environmental science and engineering. Increasingly, spatially extended, intelligent networks, of multi-variable intelligent sensor arrays are seen as the appropriate tools for studying complex real-world systems. An attractive feature for researchers is the potential for remote manipulation of experiments or observing networks in near real-time based on the incoming data. This poster highlights key findings from an NSF sponsored workshop held August 12-14th, 2003 at Scripps Institute of Oceanography, and presents recommendations on how the Foundation should proceed to ensure that cyber-infrastructure needs related to distributed, networked observing systems for the environment are met. Participants from various disciplines including environmental science, engineering, computer science, statistics, and mathematics attended the workshop, as did representatives from NSF as well as several existing or proposed large research programs (CUAHSI, NEON, CLEANER, LTER). This workshop focused on several specific themes: 1. Sensing technologies: 2. Data collection; acquisition; and fielded sensor arrays 3. Data management 4. Analysis and visualization 5. Error resiliency 6. Metadata 7. System security integrity

Estimating annual carbon exports from seasonally flooded tree islands in the southern Everglades

Date Presented: Friday Night

Lead Author: Tiffany Gann
Co-Authors: Daniel Childers
Institutional Affiliations: Florida International University
Primary Site: FCE

Abstract: Restoring freshwater flow is a critical component of Everglades restoration in part because nutrient inputs to downstream communities may be increased with increasing freshwater flow. The southern Everglades is one of the first regions to undergo hydrologic restoration, and is thus a good test for predicting the effect of large-scale Everglades restoration. In this study, part of an ongoing, long-term experiment, we characterized pool sizes and fluxes of P, N, and the primary OM cycles in southern Everglades tree islands. In seasonally flooded tree islands, leaf litterfall contributes the greatest proportion of OM, and approximately 70% is accumulated on the forest floor. Our modeling effort shows that P and N are also largely retained within the tree island system, with limited remineralization to soil porewater. However, decomposition estimates show that 30% of cocoplum leaf litter is decomposed within 18 months. We concluded: 1) these rates must be influenced by water flowing through tree islands seasonally; 2) a relatively large proportion of leaf litterfall is available for marsh ecosystem processes through decomposition; and 3) the availability of this C source will likely be influenced if loading of available nutrients increases with increasing freshwater flow. In support of these findings, we complement these calculations with data investigating the relationship between freshwater flow and litter decomposition rates in southern Everglades tree islands.

Estimating cheatgrass abundance from LANDSAT Imagery

Date Presented: Saturday Night

Lead Author: John Bradford
Co-Authors: William Lauenroth, Kenneth McGwire
Institutional Affiliations: Colorado State University, Desert Research Institute
Primary Site: SGS

Abstract: Non-native plant species have invaded many terrestrial ecosystems and previous studies have suggested that these invasions can modify plant species compositions as well as energy and nutrient cycling. To quantify the overall impact of these invasions we need to understand the spatial distribution and abundance of the invaders. Consequently, obtaining accurate and reliable distribution maps for invasive plants has become a crucial step in both research and management efforts in invaded ecosystems. We tested the ability of multi-date LANDSAT imagery to detect cheatgrass (Bromus tectorum), an annual cool season grass originally from Asia and Europe that has spread throughout much of western North America and dramatically altered many ecosystems in these areas. Cheatgrass displays early seasonal development compared to most native species. By comparing ground measurements of plant species cover with spectral response at multiple times throughout the growing season, we quantified the extent to which this phenological difference can facilitate cheatgrass detection. Using a model selection approach to determine the best transformation of the spectral data and the best statistical relationship between spectral response and ground observations, we found a significant relationship between spectral response and cheatgrass abundance (R2 = 0.647). This relationship indicates that cheatgrass detection is possible with multi-spectral imagery, and could be used to create cheatgrass distribution maps. We suggest that the strength of this relationship could be improved by either obtaining higher spatial resolution imagery that more accurately captures cheatgrass patches or by utilizing hyperspectral imagery that would allow subpixel unmixing of the observed spectra.

Evaluating the influence of historical wildfire scars and climate on NDVI changes in Alaska

Date Presented: Friday Night

Lead Author: Michael S. Balshi
Co-Authors: David L. Verbyla, A. David McGuire
Institutional Affiliations: University of Alaska Fairbanks, Fairbanks, AK
Primary Site: BNZ

Abstract: Wildfire is an important disturbance that influences the structure and function of the boreal forest and has implications for feedbacks of water, energy, and trace gas feedbacks to the climate system. This study investigates the response of 8 km Normalized Difference Vegetation Index (NDVI) Pathfinder data to: 1.)monthly temperature and precipitation, and 2.) the 1950-2002 fire scar record in interior Alaska . NDVI is a robust indicator of vegetation canopy biomass with large areal and temporal coverage. This study analyzes differences in NDVI changes between burned and surrounding unburned areas. For areas that have not burned we evaluate whether changes in temperature and precipitation are associated with changes in NDVI during recent decades. This analysis of the rates of change in NDVI will provide a better understanding of the influence of disturbance regimes (wildfire) and climatic variables (temperature and precipitation) on vegetation dynamics across interior Alaska.

Evaluation of the relative importance of nitrification and denitrification in nitrous oxide production: application of isotopomers

Date Presented: Saturday Night

Lead Author: Nathaniel Ostrom
Co-Authors: Adam J. Pitt, Robin Sutka, Peggy H. Ostrom, Timothy Bergsma, Hasand Gandhi, John Breznak
Institutional Affiliations: Geological Sciences Michigan State University, Geological Sciences Michigan State University, American Type Culture Collection, Geological Sciences Michigan State University, Kellogg Biological Station Michigan State University Geological Sciences Michiga
Primary Site: KBS

Abstract: Nitrous oxide is well known as a greenhouse gas that has been increasing in concentration in the atmosphere over the past 150 years in a manner similar to carbon dioxide and methane. Microbial nitrification and denitrification are the predominant sources of atmospheric nitrous oxide; however, their relative importance in this regard has proven elusive. Such information will be particularly valuable in agricultural environments that can be managed to foster one process or the other. Our laboratory has investigated the use of isotopomers as a potential indicator of the relative importance of nitrification and denitrification in nitrous oxide production. The term “isotopomer” refers to not only the isotopic abundance of nitrous oxide (d15N and d18O) but also to the abundance of 15N within each of the nitrogen atoms in this asymmetrical molecule. Recently, we demonstrated that the isotopomer composition of nitrous oxide provides an understanding of the pathways of production by the nitrifying bacteria Nitrosomonas europaea and Methylococcus capsulatus Bath (Sutka et al., 2003). We combine these results with experiments using laboratory cultures of whole soil microbes and pure cultures of an nitrous oxide-producing denitrifier, Pseudomonas chlororaphis (ATCC #43928) to demonstrate that the isotopomer fingerprint of nitrous oxide derived from denitrification is unique from that of nitrification. Furthermore, we have demonstrated that in agricultural soils the consumption of nitrous oxide during denitrification has no effect on site preference. With these results, we are now poised to begin applying isotopomers to apportion the relative contribution of nitrous oxide derived from nitrification and denitrification in agricultural soils and other environments.

Examining stream food webs in reaches with coniferous versus deciduous vegetation in Mack Creek, Oregon

Date Presented: Friday Night

Lead Author: Charles H. Frady¹
Co-Authors: Sherri L. Johnson², Judith L. Li¹, and Stanley V. Gregory¹
Institutional Affiliations: 1)Department of Fisheries and Wildlife, 104 Nash Hall, Oregon State University, Corvallis, OR. 97331, 2)USFS PNW Research Station, Corvallis, OR.
Primary Site: AND

Abstract: Mack Creek, in the H. J. Andrews Experimental Forest, has been the subject of intensive efforts to understand and quantify functional aspects of stream ecosystems (Sedell et al. 1975, Triska et al. 1975, Aho and Hall 1976, Anderson et al. 1978, Grafius and Anderson 1980, Hawkins 1983, Minshall et al. 1983, Anderson et al. 1984, Hawkins 1984). We examined stream food webs in two reaches of Mack Creek to explore long-term effects of contrasting land use management. Do stream reaches through old growth coniferous forests (~ 450 years) exhibit differences in invertebrate assemblages and fish diets from stream reaches through deciduous riparian zones (35+ years post harvest)? To address this, we collected juvenile and adult aquatic and terrestrial invertebrates using various sampling methods. Concomitantly, we sampled cutthroat trout (Oncorhynchus clarki) diet using gastric lavage techniques. Although early studies shortly after harvest in this stream found differences in trout and invertebrate biomass, and invertebrate community composition (Murphy and Hall 1981, Murphy et al. 1981, Hawkins et al. 1982), we found no significant differences in densities of benthic and drifting invertebrates between the coniferous and deciduous reach. Benthic invertebrate community composition and richness were similar between reaches. Infall of winged and terrestrial invertebrates was greater in the reach through deciduous vegetation. Fish diet composition was similar between reaches and included invertebrate taxa not collected using our methods. Ongoing studies are exploring how stream invertebrates respond to differences in resources in environments with contrasting riparian vegetation and detrital availability.

Examining the roles of animals in ecosystem structure and functioning across a biome transition zone: A summary of Sevilleta LTER studies.

Date Presented: Saturday Night

Lead Author: Robert Parmenter
Primary Site: SEV

Abstract: Over the last 14 years, studies of consumer groups in the ecosystems of the Sevilleta LTER site in central New Mexico have addressed numerous hypotheses concerning ecosystem patterns and processes. This report summarizes those studies with respect to long term population dynamics of important and representative vertebrate and invertebrate species, experimental manipulations of animal populations, disturbance events (ENSO, droughts and fires), top-down versus bottom-up control functions, and ecotone dynamics. The results of these studies have been incorporated into public health disease forecasting, government policy decisions on the use of prescribed fires, and increased understanding of drought impacts in the Southwest.

Experimental assessment of toads as predators of detrial food webs in a subtropical monsoon forest, Taiwan

Date Presented: Friday Night

Lead Author: Ping-Chun Lucy Hou
Co-Authors: Ching-Yu Huang, Jao-Jinn Jong, Hsin-Lin Wei
Institutional Affiliations: Department of Biology, National Cheng Kung University, Tainan, Taiwan
Primary Site: INT

Abstract: Ground-dwelling amphibians in forests are predators of many litter invertebrates, which are members of detrital food webs. Recent studies have shown that forest amphibians can decrease the density of their preys, slow down the rate of litter decomposition, and increase the amount of nutrients available for microbes and plants. The toad, Bufo bankorensis, is an active forager and one of the dominant litter amphibians in Nanjenshan subtropical monsoon forest, an LTER site in Taiwan. Diet of 180 toads by stomach flushing method consists of prey items from 97 taxonomic families. Each stomach contains 18 items on average. The toads eat predominantly ants and termites in the non-monsoon season. The major preys of the toads involve members of detrital food webs. We also setup 10 enclosures in an attempt to evaluate the predatory effects of the toad on the processes of litter decomposition. Mean density and composition of the litter invertebrates in the amphibian-excluded enclosures was similar to those in the control ones. In addition, mean decay rate in the excluded enclosures was similar to that in the control ones. Although these results suggest the toad has little effects on the litter invertebrates and the rate of decomposition, our results from tracking the toads in the forest showed that their home range is much larger than the size of the enclosure. The small size of the enclosures might interfere the toad’s foraging behavior and further studies are needed to confirm their effects on the processes of litter decomposition.

Extensive monitoring of primary productivity in Phoenix, Arizona: Methodologies and constraints

Date Presented: Friday Night

Lead Author: Chris A. Martin
Co-Authors: Sarah B. Celestian, Linda B. Stabler, Diane Hope
Institutional Affiliations: Arizona State University
Primary Site: CAP

Abstract: Scientists with the Central Arizona - Phoenix (CAP) LTER have established a multi-faceted approach for measuring ecosystem function that includes use of controlled experiments, and intensive and extensive monitoring programs. Whereas controlled experiments and intensive monitoring programs typically involve the accrual of research data for either the testing of ecological theory or the monitoring of ecosystem function over relatively short temporal and/or spatial scales, extensive monitoring programs focus on repeated measurements of ecosystem function over relatively greater spatial and temporal scales. Since 2001, our extensive monitoring of the productivity of urban vegetation has included measurements of biovolume and nitrogen sequestration of trees at 50 sites across the urban portion of the 6,400 km(SUP>2 CAP LTER region. Extensive monitoring sites were selected based on preliminary research of the Phoenix urban heat island and urban to rural atmospheric carbon dioxide gradient, a representation of urban land use types (e.g. residential, commercial, industrial and institutional), and the inclusion of a representative number of sites from the CAP LTER 200 point survey. We constrained ourselves to measurements of only trees because tree biovolumes are relatively less impacted by human management activities than other urban vegetation types, and trees are the dominant vegetation life form in the Phoenix area. The number of trees at each site ranges from 4 to 10. Each year, biovolume measurements are made for all trees in January. Additionally, 30 non-destructive measurements of leaf chlorophyll (Minolta SPAD 502 meter) per tree are made in June. Chlorophyll concentrations for trees are calculated from SPAD measurements based on laboratory-derived models of SPAD vs. actual leaf chlorophyll concentrations. Annual biovolume measurements will ultimately be fitted to allometric models to estimate tree standing biomass and aboveground net primary productivity.

External Forcing of the Antarctic Marine Ecosystem: Ocean-Atmosphere-Ice Interactions in the Palmer LTER Region

Date Presented: Saturday Night

Lead Author: Sharon Stammerjohn
Co-Authors: Doug Martinson, Raymond Smith, Richard Iannuzzi
Institutional Affiliations: Lamont-Doherty Earth Institute of Columbia University, Institute for Computational Earth System Science
Primary Site: PAL

Abstract: The western Antarctic Peninsula (WAP) region, with its direct exposure to the prevailing westerlies and its north-south climatic gradient, is a highly dynamic region that responds rapidly to climate change (Smith et al., 1999). The WAP also is relatively close to the frontal boundaries of the Antarctic Circumpolar Current (ACC) and the corresponding Circumpolar Deep Water (CDW) (Hofmann et al., 1996). Thus, the confluence of subtropical and polar air masses and water types is intensified in the WAP region and contributes to the climate sensitivity of ocean-atmosphere-ice (OAI) interactions observed there. The central tenet of the Palmer LTER is that the seasonal and interannual variability of sea ice affects all levels of the Antarctic marine ecosystem, from the timing and magnitude of seasonal primary production to the breeding success and survival of apex predators (Ross et al., 1996). In contrast to terrestrial ecosystems, external physical forcing plays a more dominant role in causing variability in marine ecosystems than internal biological mechanisms (Steele, 1991). Thus, in the context of this high latitude ecosystem, the physical forcing and possible mechanisms influencing OAI variability are an essential aspect toward understanding this marine ecosystem. Sea ice creates an ecotone that is variable in both time and space. To better understand how the spatial and temporal variability of sea-ice affects the ice-ocean system - and thus defines the physical forcing of the marine ecosystem - we examine (1) the climatologies of relevant upper ocean properties and sea-ice indices, (2) the spatial/temporal variability about these climatologies, and (3) the co-variability between ocean and sea-ice parameters. Our objective is to identify key patterns of the ice-ocean coupled system - particularly those varying with the timing of sea-ice advance and retreat - that ultimately define the forcing of the Antarctic marine ecosystem in this region.

Extrapolating Carbon Sequestration Rate from Plot to Regional Scales.

Date Presented: Saturday Night

Lead Author: Jiaguo Qi
Co-Authors: Stephen South, David Lusch, David Skole and Stuart Gages
Institutional Affiliations: Michigan State University
Primary Site: KBS

Abstract: Production of agricultural row crops takes place on 199 million acres of land across the United States. The implications and consequences of cropping methods, comprising such a large area, are far reaching. Cropping methods also affect carbon sequestration rates, conservation tillage methods have been shown to sequester carbon at a rate up to 300kg/hectare/year at the KBS LTER site, Michigan (Robertson et al., 2000). The question is whether or not we can extrapolate this result to a large spatial and temporal extent. The research objective of this study was to first to investigate the possibility of extending the current research findings at the KBS LTER site to regional scale and second was to develop a strategy to monitor temporal dynamics of land use changes (cropping methods). Satellite images centered at the KBS LTER site were used to classify the land use into no-till and till practices. We then used the carbon sequestration rate found at the LTER site to quantify the total C sequestration over large areas. A discussion on the validity of this approach and dis/advantages will be presented.

Factors Affecting Implementation of Ecology Explorers, the K-12 Education Program of CAP LTER, in the Classroom

Date Presented: Friday Night

Lead Author: Charlene Saltz
Co-Authors: Debra Banks, Monica Elser
Institutional Affiliations: Arizona State University - Center For Environmental Studies (ASU-CES), Arizona State University - Center for Research on Education in Science, Mathematics, Engineering and Technology; ASU - CES
Primary Site: CAP

Abstract: Ecology Explorers (EE) is the K-12 program of the Central Arizona-Phoenix Long-Term Ecological Research Project (CAP LTER) at Arizona State University's Center for Environmental Studies (CES). The program's goals are to: engage students and teachers in scientific research, encourage students to understand their local environment, and establish collaboration between teachers and ASU researchers. This poster presents some of the recent findings of a study on factors affecting implementation of the EE program. The conceptual framework for the study is based on immediate and long-term implementation. The samples consisted of EE cohort panels from 1998 to 2002. Some of the questions guiding the study were: What factors appear to facilitate or impede the implementation of protocols into curriculum? To what extent are the EE program methodologies being used to enhance teaching practices in inquiry, research, student experimentation, and the integration of mathematics? The analysis of the immediate perspectives suggests that within a year EE interns had their students using protocols. The significant changes in the interns were using the web more frequently for research and having their students conduct long-term experiments. In addition, the significant increase of communication with CES Ed staff appears to have a strong relationship with interns and students using spreadsheets. The analysis of the long-term perspectives suggests that the implementation of the protocols can take less than two years; whereas, using spreadsheets in the classroom may take longer. Other findings of interest were: continued support by CES Ed staff facilitates the embedding of the EE protocols into the curriculum and internal support from school administration and colleagues promotes the embedding of EE protocols through hands-on activities. These forms of support appear to aid in the establishment of a platform for introducing higher-order thinking skills through scientific inquiry.

Farm decisions, P management and water quality

Date Presented: Saturday Night

Lead Author: Pete Nowak
Co-Authors: Perry Cabot, Sarah Bowen
Institutional Affiliations: UW-Madison, UW-Madison
Primary Site: NTL

Abstract: This paper examines manure management practices on 10, contiguous animal feeding operations (AFOs) in south central Wisconsin in the Lake Mendota Watershed. Spatial patterns of soil test P (STP) in the surface 0-5 cm were used to examine soil P distribution among 217 fields. Results suggest that policy based on classifying AFOs solely on scale of operation indicators (i.e., herd sizes or animal density) will not meaningfully capture manure distribution impacts due to farm decisions at various levels levels. AFO scale indicators may be a useful tool for estimating generated manure, but we conclude that the management decisions surrounding the distribution of manure also need attention.

Flow of predatory insects in an agricultural landscape: a 14-year synthesis

Date Presented: Saturday Night

Lead Author: Stuart Gage
Co-Authors: Manuel Colunga-Garcia, Charles McKeown
Institutional Affiliations: KBS LTER, Michigan State University
Primary Site: KBS

Abstract: This research synthesizes patterns of response of eight species of Coccinellidae, generalist insect predators of plant inhabiting herbivores, to an array of management regimes in a variety of plant communities and cropping systems implemented at the KBS LTER. The work is based on a 14-year project aimed to examine ecological principles as substitutes for chemical subsidies in agricultural ecosystems. This project also relates to the LTER Network theme of trophic dynamics in space and time. Weekly species counts of adult beetles have been made from May through August at 210 permanent locations. The sample array covers all seven KBS LTER treatments, cropping rotations and plant communities. The resulting 444,000 observations of insect abundance have been stored in a relational database, and linked to 14 years of daily weather observations to provide a spatial-temporal landscape scale response to treatment and plant community regimes. In addition, a system has been developed to automate the production of distribution maps for 8 species of insect predators at intervals of 100, 200, 400 and 1200 degree days over the 14 year time span resulting in 2600 distribution maps. This spatial-temporal database is being analyzed to model the numerical response of these species to changing plant communities, cropping patterns, treatment manipulation and meteorological conditions. During the observation period we have quantified natural biological regulation of a plant herbivore, documented the outbreak of two exotic species, examined the interaction of exotic and native predators, quantified the response of species to changing plant growth and characterized long term population trends in predators.

Fluxes of water, sediments, and nutrients at the landscape scale within the Jornada Basin, New Mexico

Date Presented: Friday Night

Lead Author: Anthony J. Parsons¹
Co-Authors: John Wainwright² and Eva Műller²
Institutional Affiliations: University of Leicester, UK¹ and King’s College London²
Primary Site: JRN

Abstract: Understanding water flux is fundamental to understanding the ecology of drylands, not only because it redistributes water, but also because it redistributes sediment and nutrients. Traditionally, attempts to measure the flux of surface water (runoff) generated during rainstorms have been made using data collected from runoff plots during rainfall simulation experiments, or from runoff plots that record natural rainfall events. In this poster we report on landscape scale approaches to measuring these fluxes. We instrumented 5 stock ponds to evaluate fluxes within single vegetation communities. We installed 96 specially designed ‘miniflumes’ and combined bedload and nutrient collectors to sample interrill runoff fluxes across ecotones, and we installed 12 samplers in rills and washes to evaluate water and nutrient fluxes in concentrated flow. Preliminary results from the miniflumes show higher rates of inorganic nitrogen transfer out of the vegetation communities than do the runoff plots (by factors of between about 2 and 6). For P, the differences are not so clear-cut, and the values are much closer. Qualitative data from the stock pond records show that responses to similar rainfall events in the mesquite and creosotebush catchments are very different. The mesquite catchment is much more responsive. By contrast, plot data show runoff from the two vegetation communities to be very similar. These data are being used to test landscape-scale models of water, sediment and nutrient fluxes that are parameterised using point data on vegetation cover, ponded infiltration rates, soil moisture and soil-moisture evolution, soil texture, aggregate stability and nutrient content, and microtopography that are collected using a nested sampling strategy to quantify short- and medium-range variations of model parameters and investigate their scaling properties (See related poster by Műller, Wainwright and Parsons).

Forest Ecological Site Characteristics and Carbon Pools and Flows of the Kwangneung LTER site in Korea

Date Presented: Friday Night

Lead Author: Jong-Hwan Lim
Co-Authors: Joon Hwan Shin, Choonsig Kim, Jeong Soo Oh
Institutional Affiliations: Korea Forest Research Institute
Primary Site: INT

Abstract: The study area, Kwangneung Experiment Forest (KEF) is located on the west-central portion of Korean peninsula and belongs to a cool-temperate broadleaved forest zone. At the old-growth deciduous forest, we have established a permanent plot and a flux tower and the site was registered as a KLTER site and also a KoFlux site. In this study, we aimed to present basic ecological characteristics and carbon budgets and flows, and some monitoring data which are essential for providing important parameters and validation data for the models for forest dynamics or biogeochemistry to predict the changes in forest ecosystem structure and function. Dominant tree species were Quercus serrata and Carpinus laxiflora, and accompanied by Q. aliena, C. cordata, and so on. Density of the trees larger than 2cm in DBH was 1,473 trees/ha, total biomass 261.2 tons/ha, and basal area 28.0 m2/ha. Soil type is brown forest soil (alfisols in USDA system), and the depth is from 38 to 66cm. Soil texture is loam or sandy loam, with pH of 4.2 to 5.0. Seasonal changes in LAI were measured by hemispherical photography at the 1.2m height, and the maximum was 3.65. And the spatial distributions of volumetric soil moisture contents and LAIs of the plot were measured. Litterfall was collected in littertraps (collecting area: 0.25m2) and mass loss patterns in decomposing litter were estimated using the litterbag technique. Total annual litterfall was 5,627 kg/ha/year and leaf litter accounted for 61% of the litterfall. Mass loss by leaf decomposition was more rapid in C. laxiflora and C. cordata than in Q. serrata. The carbon pool in living tree biomass including below ground biomass was 136 tons C/ha, and 5.6 tons C/ha in the litter layer, and about 92.0 tons C/ha in the soil to the 30cm in depth. Totally more than about 233.6 tons C/ha was stored in DK site. And then we have drawn a schematic diagram of carbon budgets and flows in each compartment of the KEF site.

Frass from Canopy Herbivores Increases Soil Nitrogen, Carbon, and Nitrogen Export from Quercus rubra Mini-ecosystems

Date Presented: Friday Night

Lead Author: Christopher J. Frost
Co-Authors: Mark D. Hunter
Institutional Affiliations: University of Georgia
Primary Site: CWT

Abstract: Increased nitrogen (N) mobilization and export from forest ecosystems following canopy herbivory has been well documented, though the mechanism behind the loss is not clear. Insect frass (feces) is an appealing candidate because up to 86% of the leaf nitrogen consumed by the herbivore ends up in frass and the nitrogen is in labile forms. Herbivore-mediated changes in N distribution may affect above- and belowground trophic systems and carbon (C) distribution. Because nitrogen is often a limiting nutrient in forest systems and carbon often provides the energy source for nitrogen transformations, understanding the mechanisms behind an insect herbivore-mediated transfer of nitrogen from terrestrial to aquatic components of a watershed is important. We initiated a replicated mini-ecosystem experiment to test three hypotheses that frass from canopy herbivores contributes to 1) increases in soil nitrogen, 2) nitrogen export as dissolved inorganic nitrogen (DIN), and 3) an increase in soil respiration due to microbial oxidation of frass carbon. One hundred and sixty nursery-grown Red Oaks (Quercus rubra) were transplanted to 7-gallon pots with soil and litter from watershed 27 at the Coweeta Hydrologic Laboratory in North Carolina and overwintered in experimental pot stands. Approximately 6 weeks following budburst (June 5, 2002), trees were subjected to insect damage, mechanical damage, or left as undamaged controls. Frass from the herbivore-damaged trees was collected and redistributed to half of each of the damage groups, creating a 3x2 factorial experimental design. Frass increased soil ammonium (NH4+) and leachate nitrate (NO3-) concentrations relative to controls. Frass did not increase soil respiration, though an apparent increase in the surface soil microbial biomass was observed. This study provides the first mechanistic evidence that frass increases the soil pool of inorganic nitrogen and the export of nitrogen from the surface soil.

Freshwater Pulsing Affects Sedimentation, Organic Matter Accumulation and Vertical Accretion of GCE Estuarine Marshes

Date Presented: Friday Night

Lead Author: Christopher Craft
Co-Authors: Chrissy Pruett
Institutional Affiliations: Indiana University
Primary Site: GCE

Abstract: We measured vertical accretion, sedimentation and soil organic matter accumulation in nine estuarine marshes that vary in freshwater versus marine inputs of water and sediment to assess the role of freshwater pulsing on stability of Georgia Coastal Ecosystem (GCE) marshes. We hypothesize that the interaction between tidal flooding and freshwater discharge mediates marsh vertical growth by controlling rates of mineral sedimentation and soil organic matter accumulation. Cesium-137 derived vertical accretion (3.8+0.3 mm/yr), sedimentation (1060+390 g/m2/yr) and organic C (110+1 g/m2/yr) accumulation were greater in estuarine marshes of freshwater-dominated watersheds (Altamaha River) than in marshes of marine-dominated watersheds (Sapelo River, Doboy Sound) (1.5+0.2 mm/yr, 660+260 g sediment/m2/yr, 40+4 g C/m2/yr). Percent soil organic matter (SOM) was greater in freshwater-dominated marshes (20+4%) than in marine-dominated marshes (8+2%), suggesting that SOM was proportionally more important to marsh accretion in freshwater-dominated watersheds. Within a given watershed, no clear difference was observed in vertical accretion, sedimentation or organic C accumulation along the gradient from terrestrial to marine-dominated marshes. Across all sites, accretion, sedimentation and organic C accumulation were consistently greater in levee marshes as compared to the interior marshes. Most GCE marshes appear to be in equilibrium with apparent sea level rise along the Georgia coast (1.6 mm/yr). Exceptions include (1) marshes along the freshwater-dominated Altamaha River where vertical accretion is greater than the current rate of sea level rise and (2) incipient marshes developing on submerging uplands of marine-dominated watersheds where freshwater and sediment inputs are low. Additional work using Pb-210, feldspar marker layers and surface elevation tables (SET’s) is underway to evaluate patterns of marsh accretion over temporal scales of months to centuries.

Gene flow in a metapopulation of black-tailed prairie dogs on the shortgrass steppe-LTER

Date Presented: Saturday Night

Lead Author: Lisa Savage
Co-Authors: Mike Antolin
Institutional Affiliations: Colorado State University
Primary Site: SGS

Abstract: Black-tailed prairie dog populations on the shortgrass steppe (SGS) Long Term Ecological Research (LTER) site in northern Colorado currently experience metapopulation dynamics: populations have been fragmented by land-use change and eradication efforts, and the bubonic plague (Yersinia pestis) causes almost 100% mortality in black-tailed prairie dog colonies and creates a dynamic of regular colony extinction and recolonization. Whether or not a metapopulation can maintain genetic diversity in the face of regular extinction depends not only on the extinction rate, but also on the extent of gene flow between populations and the composition of dispersers. Using six microsatellite markers and a 456-bp portion of the mitochondrial control region from thirteen colonies of black-tailed prairie dogs in 1997, six colonies in 2000, and five colonies in 2001, we sought to determine the extent of gene flow within a metapopulation of black-tailed prairie dogs on the shortgrass steppe-LTER. We found a high level of migration between colonies, as measured by assignment and exclusion tests, and that male prairie dogs are dispersing farther than female prairie dogs. We also found a moderate level of genetic differentiation between colonies on the SGS-LTER. The level of differentiation decreased between 1997 and 2001, a time period in which none of the study colonies went extinct from plague. Thus, it appears gene flow between colonies is high enough to decrease differentiation between plague epizootics.

Genetic diversity and clonal structure of the salt marsh perennial Borrichia frutescens

Date Presented: Friday Night

Lead Author: Christina Richards
Co-Authors: L.A. Donovan, R. Mauricio, J.H. Hamrick
Institutional Affiliations: University of Georgia
Primary Site: GCE

Abstract: We used enzyme electrophoresis to evaluate fine-scale population genetic structure of Borrichia frutescens L., a coastal salt marsh perennial in the southeastern U.S. We hypothesized that the extreme environmental gradients in this habitat would lead to high genetic structure compared to other outcrossing perennial species and to genetic differences among plants in different microhabitats along the gradients. We also hypothesized that at very fine spatial scales, extensive ramet production would cause subpopulations to be dominated by a few large clones. To test these hypotheses, we sampled individuals from populations representing the full distribution of this species in the marshes of Sapelo Island, GA. At 5 sites, leaf tissue was collected from 96 individuals at 1 m intervals on grids spanning the environmental and height gradients. Fifty-eight percent of the 17 loci examined were polymorphic, with 41.2% polymorphic within populations. Our estimate of genetic structure for Borrichia (GST = 0.069) was slightly lower than other outcrossing, long-lived perennial species (GST = 0.094, Hamrick and Godt 1996), indicating no barriers to gene flow. There was no evidence of genetic differentiation among microhabitats within populations or association of alleles with microhabitats. Within populations, average GST among microhabitats was 0.032. Across populations, genetic diversity (He) was equivalent for the three microhabitats (average He = 0.089). Clonal diversity varied (complement of Simpson’s diversity index ranged from 0.87 to 0.98), but all populations contained many multilocus genotypes, indicating that both sexual reproduction and recruitment from seeds are important factors maintaining diversity. In conclusion, we found no evidence of fine scale genetic differentiation between microhabitats within populations at these putatively neutral allozyme loci.

Global scale NDVI of arctic tundra landscapes: what does it really tell us?

Date Presented: Friday Night

Lead Author: Natalie T. Boelman
Co-Authors: Marc Stieglitz, Kevin L. Griffin
Institutional Affiliations: Lamont-Doherty Earth Observatory, Columbia University
Primary Site: ARC

Abstract: In order to accurately interpret global scale NDVI datasets, it is crucial that we better understand how the high spatial heterogeneity of arctic tundra vegetation translates into a single, large-scale NDVI pixel value acquired from a satellite. We have established relationships between photosynthetically active aboveground biomass to NDVI in two of the three dominant tundra vegetation communities (wet sedge, r2=0.84 and moist tussock, r2=0.95) at Imnavait Creek, Alaska (68 37’ N, 149 32’ W). These data demonstrate that the relationship between NDVI and aboveground biomass varies considerably between vegetation communities and therefore the interpretation of global scale NDVI values may not be straightforward. We also compared spectral data sampled from various altitudes (1 m, 4 m, 15 m, 50 m, 100 m, 1.7 km and 705 km), and yielding different field of view (FOV) sizes. A handheld spectroradiometer fitted with a 20 field of view (FOV) restrictor was used to acquire NDVI values from the 1 m to 1.7 km sampling distances using extension poles on the ground or mounted on a helicopter. We have also included NDVI values for Imnavait Creek derived from the Landsat, MODIS and AVHRR sensors orbiting at several hundered kilometers above the earth. These data show that there is a significant change in NDVI values between a FOV of approximately 2 m₂ and 20 m₂. NDVI values derived from FOVs less than 2 m₂ average to 0.44, while NDVI values derived from FOVs greater than 2 m₂ average to 0.53. These results suggest that sampling scale is important to consider when using plot level spectral sampling as a means of ground-truthing satellite-derived reflectance data.

Grassland plant functional groups exhibit inherent photosynthetic differences under non-limiting conditions.

Date Presented: Saturday Night

Lead Author: Jesse Nippert
Co-Authors: Phil Fay, Alan Knapp
Institutional Affiliations: Kansas State University, University of Minnesota Duluth
Primary Site: KNZ

Abstract: The maximum rates of Rubisco carboxylation (Vcmax) and electron transport (Jmax), as well as the apparent (Φ) and maximal (Fv/Fm) quantum yields of photosystem II were measured in eight common tallgrass prairie plant species. The species can be categorized by three functional types: leguminous (three species), forbs, non-leguminous (three species) and C4 grass (two species). Forbs were randomly planted as seedlings, followed by the dispersal of grass seed in sixty-four aboveground outdoor microcosms. The plants were well watered and experienced no light limitations during establishment and development. Our results indicate that significant photosynthetic differences exist between both functional type and species. Among forb species, non-leguminous species had significantly higher values of Jmax and Vcmax than leguminous species (p < 0.05). Chlorophyll fluorescence also varied by species and functional type, but most noticeably between the grasses and forbs. The grass species had significantly lower Fv/Fm and Φ values than the forb species. Plant water potential varied among species despite equal watering. Grass species had significantly lower pre-dawn and mid-day water stress compared to the herbaceous species. These results suggest that functional differences exist between forb and grass species as well as between the forb functional types. In addition, our results suggest the dominance of C4 grass species in the tallgrass prairie may not exclusively exist from high photosynthetic potential, but from greater resource allocation or other mechanisms which alleviate seasonal environmental stress.

Growth Strategies of Four salt marsh plants on Mankyung Estuary

Date Presented: Friday Night

Lead Author: Byung-Sun, Ihm
Co-Authors: Jeom-Sook, Lee
Institutional Affiliations: Department of Biology, Kunsan National University, Korea
Primary Site: INT

Abstract: The emergence of seedling , the length of root and shoot, and the biomass of four dominant species were measured as well as shore height to investigate their growth strategy on the salt marsh of Mankyung river Estuary in Korea. Four salt marsh plants manifested a distinguished zonation, such as Suaeda japonica dominantly spread around the low salt marsh, Atriplex gmelini and Aster tripolium, in the middle, and Suaeda asparagoides, in the upper part of the marsh. In terms of emergence of seedlings, Suaeda japonica appeared first followed by Atriplex gmelini, Suaeda asparagoides, and Aster tripolium. The growth strategies of halophytes are as follows: Suaeda japonica germinated earlier than the other plants so that its root grew rapidly and extensively at the beginning of growth. This species adopted the continuous germination strategy, allowing growth whenever a favorable condition is provided. Atripex gmelini germinated later than Suaeda japonica, as a quasi-simultaneous germination type, it showed the highest germination rate within the shortest time. Aster tripolium was germinated later than any other halophyte. Since this species exhibited characteristics between the continuous germination type and the quasi-simultaneous germination type, it did not show very high germination rate. Instead, it showed continuous germination and consistent growth of both above-ground and underground parts. Suaeda asparagoides showed especially high emergence rate at the beginning of its growth. However, the high density retarded its growth until the middle stage. Its root extended longer than other halophytes, allowing it to grow well in dry condition of upper marsh.

Harmful Algal Blooms in the Santa Barbara Channel

Date Presented: Saturday Night

Lead Author: Clarissa Anderson
Co-Authors: Mark Brzezinski
Institutional Affiliations: University of California, Santa Barbara
Primary Site: SBC

Abstract: The Spring season in the Santa Barbara Channel is typically characterized by strong, alongshore upwelling events that transport deep, cold water to the surface. As part of the SBC LTER project, we currently conduct seasonal surveys of channel-wide water chemistry, physical properties, and phytoplankton community structure to understand the annual and interannual variability in these parameters at the regional scale. For two consecutive years, the Spring bloom of phytoplankton that accompanies upwelling in the SBC has been dominated by the neurotoxin-producing diatom, Pseudonitzschia spp. Microscopy and HPLC analyses have revealed that concentrations of the diatom and its toxin, domoic acid, vary spatially throughout the channel. The distribution of phytoplankton was tied closely to physical processes transporting and concentrating phytoplankton cells in surface waters. In 2002, cells were most concentrated in upwelled waters that had warmed from 10 to 13 °C. In 2003, a very large bloom was present throughout the Channel, but was most intense within a mesoscale eddy in the western end of the basin. Correlations between distributions of this HAB and concurrent physical structure in the channel will help elucidate mechanisms for Spring bloom formation and persistence.

Harvard Forest Research on Land-use History as a Driver of Current Ecological Processes

Date Presented: Friday Night

Lead Author: John O'Keefe
Primary Site: HFR

Abstract: The forests of the northeastern United States present a history of almost continual change, albeit change that has varied greatly in scale, rates, and causes through time. The importance of human disturbance relative to natural disturbance has steadily increased, most rapidly and dramatically following European settlement. Legacies from the clearing and plowing, grazing, burning, and cutting from the 17th through 19th centuries strongly influence most ecological processes in the region today. Harvard Forest has been investigating these influences for nearly a century, as exemplified by the famed Land-use History dioramas in the Fisher Museum at Harvard Forest and, more recently, through its research as a National Science Foundation (NSF) Long-Term Ecological Research (LTER) site. Virtually every ecological process studied, from vegetation species distribution and wildlife dynamics through carbon and nitrogen cycling, reflects a legacy of land-use history. The perceived impact of land-use history on forests across the northeast today depends upon the scale at which the landscape is viewed. At the local scale, differing ownership, use, and time of abandonment of individual parcels create a patchwork of different forest types and ages with sharp edges. Once established, these patches tend to be maintained by ongoing management differences. On the other hand, at the regional scale, the pre-settlement distribution of species, largely along gentle climatic gradients, has been altered by common land-use, resulting in a general homogenization of vegetation across the region. Moreover, there is some paleoecological evidence that human activity may have acted to speed up already established environmental trends. Separating human and environmental drivers of ecological change requires at least a millennial perspective. It is critical that environmental decision-making begin with a knowledge and appreciation of the history and dynamic nature of our landscape.

Hierarchy of observations from the survey line fire on the floodplain of the tanana river in Interior Alaska

Date Presented: Friday Night

Lead Author: Jamie Hollingsworth
Co-Authors: Marilyn Walker1, Wendy Davis, Justin Epting, Isla Myers-Smith
Institutional Affiliations: University of alaska Fairbanks
Primary Site: BNZ

Abstract: Hierarchy of Observations from the Survey Line Fire on the Floodplain of the Tanana River in Interior Alaska Jamie Hollingsworth Boreal Ecology Cooperative Research Unit, University of Alaska Fairbanks Marilyn D. Walker USDA Forest Service, PNW Station Wendy Davis Bonanza Creek Long Term Ecological Research, University of Alaska Fairbanks Justin Epting Department of Forest Sciences, University of Alaska Fairbanks Isla Myers-Smith Institute of Arctic Biology, University of Alaska Fairbanks The boreal forest is the second largest biome in the world and considered one the most susceptible to changes in climate. In addition, large-scale natural disturbances such as fire are critical to its structure and functioning. In interior Alaska, discontinuous permafrost also greatly affects the role that fire plays on the system. In June of 2001, a 45,000 ha fire started 30 km south of Fairbanks Alaska and within 5 km of the Bonanza Creek LTER site. This provided a unique opportunity tostudy the effects of fire on permafrost for successional trajectories along the Tanana River floodplain. Here, we present threellevels of observations of this landscape. Satellite imagery acquired pre and post fire and then classified, aerial photographs flown one month after the fire stopped burning. Finally, ground and plot level observations were used to look at fire intensity, age of stands burned, forest community type burned, and initial regeneration patterns. This gives an overview of the multi-dimensional effects of wildland fire and permafrost on this landscape.

Highlights from the Baltimore Ecosystem Study: Urban Legends and Untested Management Assumptions

Date Presented: Friday Night

Lead Author: Steward T.A. Pickett
Primary Site: BES

Abstract: Urbanization is one of the major alterations of ecosystems on both global and national scales. A growing data base on the structure and function of the Baltimore ecosystem permits us to evaluate assumptions that if unchallenged, can impair the understanding and management of metropolitan ecosystems. Using data provided by members of the Baltimore Ecosystem Study Long-Term Ecological research project, the veracity of several reasonable hypotheses and assumptions are evaluated: 1. Ecological processes in cities and suburbs are overwhelmed by human alterations. 2. Class, Income and ethnicity explain environmental quality differences. 3. The diversity of urban biota is low and lacks floristic and faunistic value. 4. Environmental equity affects only non-whites. 5. Urban social systems are unaffected by environmental change. 6. Riparian areas are sinks for nitrate in watersheds. 7. Lawns are bad. 8. Urban land use change decreases stream water quality. 9. Land use and land cover represent urban heterogeneity. 10. All urban soils are highly disturbed and unproductive. 11. Social and ecological processes occur at the same scales. 12. Conversions to urban land uses always result in a net loss of C from above- and below-ground pools. This dozen urban legends have management implications, and challenging the assumptions with our growing data set may enhance the environmental quality of cities, suburbs, and the land beyond.

Hillslope and Streamwater Nutrient Dynamics following Upland Riparian Vegetation Disturbance in the Southern Appalachians

Date Presented: Friday Night

Lead Author: J. Alan Yeakley¹
Co-Authors: David C. Coleman², Bruce L. Haines², Brian D. Kloeppel², Judy L. Meyer², Wayne T. Swank³, Susan Steiner²
Institutional Affiliations: ¹Portland State University, Portland, OR 97207-0751 USA; ²University of Georgia, Athens, GA 30602 USA; ³Coweeta Hydrologic Laboratory, USDA-Forest Service, Otto, NC 28763 USA
Primary Site: CWT

Abstract: We investigated effects of rhododendron removal and of natural blowdown of canopy trees on nutrient export to streams in the southern Appalachians over a 9 year period. Transects were instrumented on adjacent hillslopes in a first order watershed at the Coweeta Hydrologic Laboratory (35 03 N, 83 25 W). Dissolved organic carbon (DOC), K⁺, Na⁺, Ca²⁺, Mg²⁺, NO₃^--N, NH₄⁺-N, PO₄^3-, and SO₄^2- were measured for two years prior to disturbance. In August 1995, a rhododendron thicket was basally cut and removed on one hillslope, accounting for 30% of total woody biomass. In October 1995, Hurricane Opal uprooted nine canopy trees on the other hillslope, downing 81% of total woody biomass. Following cutting, only minor responses in soilwater nutrients were seen on the rhododendron cut slope, with no effect on streamwater nutrients. In contrast, during three years following canopy tree windthrow due to the hurricane, soilwater NO₃^--N on the storm-affected hillslope showed persistent 500-fold increases, groundwater NO₃^--N increased by fourfold, and streamwater NO₃^--N doubled. Significant changes also occurred in soilwater pH, DOC, SO₄^2-, Ca²⁺ and Mg²⁺. By the end of the sixth year following disturbance, streamwater levels of NO₃^--N had returned to background levels, although soilwater NO₃^--N concentrations remained slightly elevated. Our results suggest nutrient uptake by canopy trees is a key control on NO₃^--N export in upland riparian zones, and that streamwater nutrient responses to localized riparian windthrow in upland forested watersheds may last as long as half a decade.

Historical Data Collection for the Baltimore Ecosystem Study

Date Presented: Friday Night

Lead Author: Christopher G. Boone
Primary Site: BES

Abstract: Long term ecological change cannot be understood without an assessment of human activities over time. This poster outlines data sources and methods of data collection and analyses to reconstruct past human landscapes. Research to date has focused on acquiring data around five themes: (i) land use; (ii) demography; (iii) public health; (iv) decision-making, and; (v) infrastructure provision. All factors have had significant impacts on the human ecosystem of Baltimore. The approach for the BES can serve as a model for historical research at other LTER sites. Preliminary analyses of historical census data are demonstrated. Spatial data are organized in a Geographic Information System (GIS). Future work will examine methods of incorporating qualitative and aspatial information into the GIS and a proposed BES site-wide geospatial database.

Historicizing ecological restoration: a case study of a California coastal wetland

Date Presented: Saturday Night

Lead Author: Anita Guerrini¹
Co-Authors: Jenifer Dugan ²
Institutional Affiliations: Department of History ¹, Marine Science Institute ², University of California, Santa Barbara, CA
Primary Site: SBC

Abstract: Coastal wetlands in California are under intense pressure from encroaching development and changing land uses in surrounding watersheds. Remaining coastal wetlands are critical habitat for a range of threatened plant and animal species, serve as nurseries for marine fishes and may be important to nearshore water quality. Coastal wetlands and surrounding uplands are the focus of numerous active restoration efforts by local, state and federal agencies. We are using a coastal wetland area in the SBC-LTER as the focus of a case study on the integration of historical methods and values into restoration ecology, as well as the integration of ecological values into environmental history. Restoration ecology has as its goal the restoration of a landscape to a more "natural" state, usually defined as before European occupation. But this goal has been vaguely defined in historical terms, and often ignores significant human uses both by indigenous peoples and by European immigrants. Historical documents, maps and photos can significantly aid in understanding the ecological and human history of a particular site. By integrating human history and historical methods into restoration ecology, as well as by integrating certain ecological values into environmental history, we hope to provide restoration ecology with a broader perspective in terms both of time and of place, and one in which humans are part of the landscape.

History of coffee cultivation determines soil nutrients and tree species composition in the Luquillo Experimental Forest (LUQ), Puerto Rico.

Date Presented: Saturday Night

Lead Author: Jess Zimmerman
Co-Authors: R. M Kalwani, M. Warren, and L. Rohena.
Institutional Affiliations: University of Puerto Rico, Pennsylvania State University
Primary Site: LUQ

Abstract: We compared an abandoned shade-coffee plantation (abandoned in 1928) and neighboring areas of secondary forest (selectively logged) to test whether land-use history effects on tree species composition were determined by differences in soil nutrients. The shade-coffee plantation, located at El Verde Field Station, was cultivated using the leguminous nitrogen-fixing tree species, Inga vera. We also found evidence that the coffee cultivators were using limestone to elevate the pH of the soil in the coffee plantation. Differences in soil C/N ratio, and soil nutrient availability (N-mineralization, Ca, Mg, Mn) were significant between the two forest types. Forest structural characteristics, basal area and density were not significantly different between forest types. Overall woody species richness was slightly but significantly greater in the forest than in abandoned coffee. Differences in species composition, however, were quite significant with many species being more abundant in one or the other forest type and few species shared between the two. Comparison of the distributions of adults and seedlings indicated that species concentrated in one land use type were not dispersing across the border of the former coffee plantation and establishing in the other land use type. The lack of dispersal of plant species across the border of the coffee plantation suggests that differences in soil nutrients from past land-use has altered the competitive balance among species, leading to the maintenance of differences in species composition due to past land-use history.

Human Socioeconomic Factors and Avian Diversity: A Cross-Site Comparison

Date Presented: Friday Night

Lead Author: Paige Warren
Co-Authors: Charles Nilon
Institutional Affiliations: Virginia Tech, University of Missouri - Columbia
Primary Site: CAP

Abstract: A variety of measures have been advanced as predictors of biodiversity in urban areas, such as human population density, building density, and canopy cover. These measures, either singly or in combination, describe only a portion of the habitat structure that is important for wildlife. For example, neighborhoods with the same housing density can be landscaped with different kinds of plants. In our studies of small, residential parks in Phoenix, Arizona, we found that the socioeconomic status (SES) of the neighborhoods around the parks was one of the best predictors of bird community structure within them. Human behaviors, values, and resource consumption levels, which may vary by SES, can influence factors such as the habitat and food availability for other organisms. An advantage of using SES’s over direct measures of the ecological factors influencing biotic communities is that information on SES is widely available. We tested whether human SES showed a similar correlation with avian species richness in parks in two cities: Phoenix and Baltimore, Maryland. We used PRIZM market cluster data to classify the SES of the neighborhoods surrounding the parks. Since PRIZM use the census block group as its geographical unit, we treated the set of block groups immediately surrounding each park as its neighborhood, selecting only parks found in relatively homogeneous neighborhoods with respect to PRIZM market clusters. We found that bird species richness is indeed correlated with SES in both cities, but SES explains much higher proportions of the variance in Phoenix. Birds in Baltimore appear to be less sensitive to differences associated with human SES and more sensitive to overall human density than birds in Phoenix. In addition, bird diversity in Baltimore parks also appears to be more strongly area-dependent than in Phoenix. We propose several possible reasons for these differences between the two cities.

Hurricanes, Climate, and Nutrient Availability Drive Litterfall Production in the Luquillo Experimental Forest

Date Presented: Saturday Night

Lead Author: Matthew Warren1
Co-Authors: Jess K. Zimmerman1, Xiaoming Zou1, D. Jean Lodge2, and Lawrence Walker3
Institutional Affiliations: Institute for Tropical Ecosystem Studies, University of Puerto Rico1, USDA Forest Service2, University of Nevada, Las Vegas3
Primary Site: LUQ

Abstract: Understanding how tropical forests respond to changing disturbance and climate has become a major concern because of their role in the global carbon cycle and maintenance of biodiversity. The first step in accurately predicting how ecosystems will respond to a changing environment is to assess the factors which drive ecosystem processes, and the long term response of ecosystem processes to disturbance. This study evaluates annual variation in litterfall production in control and fertilized plots at El Verde (EV), a lowland forest, and Pico del Este (PE), a cloud forest, within the Luquillo Experimental Forest. Stepwise regression analyses were done to relate variation in annual litterfall production to hurricane disturbance, temperature, and precipitation. Years since last hurricane disturbance (YSH) had a significant influence on annual litterfall production in both control and fertilized plots at both sites. Average annual maximum temperature was also a significant factor for both treatments in EV, but only in fertilized plots in PE. Average annual minimum temperature was a significant factor for total litterfall in PE control plots. Precipitation was only a significant factor for leaffall in EV. Using climate variables and YSH, regression models explained 59% - 95% of the variance in annual total and leaf litter production in control and fertilized plots in EV and PE. The results from this study suggest that litterfall production in the LEF can be predicted with reasonable accuracy using climate and hurricane frequency parameters, and nutrient availability interacts differently with these factors in the lowland and cloud forests.

Impact of fertilization on the abundance of two detritivorous snails

Date Presented: Friday Night

Lead Author: Caroline McFarlin¹
Co-Authors: Tracy L. Buck,^2,4 Steven Y. Newell,² Steven C. Pennings³
Institutional Affiliations: ¹The University of Georgia, Athens, GA; ²The University of Georgia Marine Institute, Sapelo Island, GA; ³The University of Houston, Houston, TX; ⁴Belle Baruch Marine Institute, The University of South Carolina,
Primary Site: GCE

Abstract: Because of anthropogenic alterations to the global nitrogen cycle, there is increasing interest in how nutrient supply affects community structure and processes. Most fertilization studies have focused on changes in plant biomass or community composition, and only a few studies have examined how nutrient effects propagate through the food web. Salt marshes are particularly vulnerable to eutrophication because they receive nutrient inputs from adjacent watersheds. Here we examine the impact of fertilization on two detritivorous snails that feed on litter from two abundant salt marsh plants, Spartina alterniflora and Juncus roemerianus, at 19 sites within the Georgia Coastal Ecosystems LTER study area. In control and fertilized plots, densities of both snail species were positively correlated with nitrogen content of live Juncus, but were not correlated with nitrogen content of live Spartina, nitrogen content of litter from either plant species, or plant biomass (live or litter). The two snail species were negatively correlated with each other in each treatment, supporting previous studies suggesting that they compete. Fertilization significantly increased nitrogen content of live plants of both species, but did not affect the nitrogen content of either litter type, perhaps because plants resorbed nutrients from senescing leaves or because litter was in variable states of decay. Fertilization increased the biomass of Spartina litter and decreased the biomass of Juncus litter, but did not alter densities of either snail species, nor did it alter the negative correlation between species. Sites differed strongly in snail numbers, irrespective of experimental treatments.Our results suggest that impacts of eutrophication may not propagate through the food web to affect detritivore densities, possibly because eutrophication may not strongly affect litter quality, or because other factors such as competition and predation may more strongly mediate detritivore densities.

Impact Of Macroalgal Mats On Per Capita Grazing Rates In A Temperate Coastal Lagoon

Date Presented: Saturday Night

Lead Author: Jennifer Rosinski
Co-Authors: Karen J. McGlathery
Institutional Affiliations: University of Virginia, Department of Environmental Sciences, Charlottesville, VA 22904-4123
Primary Site: VCR

Abstract: Macroalgal blooms and the associated habitat changes alter the composition and abundance of macrofauna and alter trophic relationships. We conducted field experiments using an amphipod, Ampithoe rubricata, and a snail, Astyris lunata, as grazers on different densities of macroalgae in Hog Island Bay, a shallow coastal lagoon in the Virginia Coast Reserve to determine the impact of grazing on macroalgal proliferation. Per capita grazing rates for both grazers were highest at the mid-algal density (equivalent to 1500-g ww/m2) on both Gracilaria tikvahiae and Ulva lactuca in summer 2001 but only on G. tikvahiae in fall 2002. This algal density is similar to average field biomass and may provide an optimum balance of food quality and refuge for the grazers. Amphipods were able to graze >100% of new algal biomass at low and mid-algal densities but were unable to control new growth at high algal density. The high initial algal density may allow the algae to escape the grazing pressure of the amphipods. Snails showed a similar trend in controlling new algal biomass but control was reduced at mid-algal density. At low to medium algal densities, grazers may be able to temporarily reduce retention of nitrogen in algal tissue.

Impacts of Agricultural Land Use on Aquatic Communities in Small Temperate Coastal Watersheds: The Use of Benthic Macroinvertebrates as Bioindicators of Nutrient Enrichment

Date Presented: Saturday Night

Lead Author: Diane Barnes
Co-Authors: Karen McGlathery, Jay Zieman
Institutional Affiliations: University of Virginia, Virginia Coast Reserve LTER
Primary Site: VCR

Abstract: Salt marshes and shallow coastal lagoons are important and dynamic features along many coastlines of the world. Tidal creeks are a vital component of salt marsh-lagoon ecosystems, as they are the primary linkage between land and sea, and serve as a conduit for transfer of materials from terrestrial catchments to coastal waters. During recent history, anthropogenic activities in coastal watersheds have greatly increased transport of nutrients through rivers to offshore waters. Nutrient pollution has been demonstrated to have many adverse effects on aquatic ecosystems, including increased incidence and duration of toxic algal blooms, degradation of seagrass beds and coral reefs, fish kills, shellfish poisoning, and an overall decrease in biological diversity. Benthic macroinvertebrates have been used in biological monitoring and assessment of nutrient pollution in many coastal regions of the world. However, much of this research has focused on systems with large watersheds in which point source pollution is dominant. The Virginia Coast Reserve, located on the Eastern Shore of Virginia, consists of a number of adjacent, small catchments similar in size, shape, climate, and topography, but varying in percentage of land in agricultural use. The structure of this landscape allows for analysis of the effects of non-point source nutrient pollution on aquatic communities in small watersheds, using a multiple watershed approach within a relatively small regional area. The overall objective of this work is to examine the impacts of agricultural land use on aquatic communities in small temperate coastal watersheds. These impacts will be assessed through monitoring a variety of chemical, physical, and biological parameters in conjunction with the use of benthic macroinvertebrates as bioindicators of nutrient enrichment.

Implications of global change for plant reproduction: consequences for community structure

Date Presented: Friday Night

Lead Author: Janneke HilleRisLambers
Co-Authors: Stan Harpole, Stefan Schnitzer, Peter Reich, David Tilman
Institutional Affiliations: University of Minnesota
Primary Site: CDR

Abstract: The effects of global change on plant communities will depend on how plant species are differentially affected by factors such as elevated carbon dioxide, nitrogen deposition and declining diversity. Understanding the effects of global change on recruitment limitation is particularly important, because plant early life history stages can strongly influence diversity, succession and invasion dynamics. Unfortunately, the effects of environmental variables on plant reproduction are poorly studied outside of agricultural systems. Here we quantify the effects of elevated CO2, nitrogen, and diversity on seed production of 8 perennial plant species to determine 1) whether species will differ in their response to these global change factors and 2) whether species within four functional groups (C3 grasses, C4 grasses, legumes, forbs) respond similarly to these global change factors. We found that changes in seed production under elevated CO2 and nitrogen varied by species (from no effect to increased seed production), and that species within functional groups did not respond similarly to elevated CO2 and nitrogen. Seed production of a few species increased at higher species richness, most likely due to the disproportionate effects of insect seed predators at high density (low diversity). Allocation to reproduction (i.e. seed biomass/total biomass) declined for many species at elevated CO2 and nitrogen levels. Our results suggest that elevated CO2, nitrogen deposition and declining diversity may strongly affect plant communities through differential effects on seed production.

Influence of landscape position and vegetation on long-term weathering rates at Hubbard Brook Experimental Forest, New Hampshire, USA

Date Presented: Friday Night

Lead Author: Carmen Nezat
Co-Authors: Joel D. Blum, Andrea Klaue, Chris E. Johnson, and Thomas G. Siccama
Institutional Affiliations: University of Michigan, Syracuse University, Yale University
Primary Site: HBR

Abstract: The spatial variability of long-term chemical weathering in a small watershed was examined to determine the effects of landscape position and vegetation. We sampled soils from forty-five soil pits within an 11.8-hectare watershed at the Hubbard Brook Experimental Forest, New Hampshire. The soil parent material is a relatively homogeneous glacial till deposited ~14,000 years ago and is derived predominantly from granodiorite and pelitic schist. The area is dominated by northern hardwoods, but conifers are abundant in the upper third of the watershed. The average long-term chemical weathering rate in the watershed (40 meq m^-2 yr^-1), calculated by the loss of elements from the soil profile, is similar to rates in other ~10 to 15 ka old soils developed on granitic till in temperate climates. Despite the homogeneity of the soil parent material in the watershed, long-term weathering rates decrease by a factor of three over a 260 m decrease in elevation. The large intra-watershed variability across this small area demonstrates the need for extensive sampling to obtain representative estimates of long-term weathering rates. The present-day loss of base cations from the watershed, calculated by watershed mass balance, is twice the long-term weathering rate indicating that the pool of exchangeable base cations in the soil is being diminished.

Influence of soil management on bacterial morphotype diversity in soil aggregates.

Date Presented: Saturday Night

Lead Author: Heather Dopp
Co-Authors: E.J. Park, A.J.M. Smucker
Institutional Affiliations: Michigan State University
Primary Site: KBS

Abstract: Soil aggregation processes and wetting-drying cycles differentiate microhabitats by changing pore networks and sequestering carbon within soil aggregates. Bacterial morphotype analysis can be indicative of bacterial populations associated with the microhabitats within soil aggregates. We identified bacterial morphotypes by image processing (CMEIAS – Center for Microbial Ecology Image Analysis System; Michigan State University) of bacteria stained with DTAF (5-(4,6-dichlorotriazin-2-yl)aminofluorescein), extracted from exterior and interior regions of soil aggregates. The diversity and the number of bacteria were compared with carbon and nitrogen concentrations, soil texture, and mean weight diameter (MWD) of aggregate by wet sieving. Soil carbon contents in exterior regions of aggregates were 5% and 11.7% greater than interior regions of soil aggregates from KBS and UP. Greater diversities of bacterial morphotypes, and increased numbers of bacteria were expected in the exterior regions of soil aggregates that have greater C and N concentrations and porosities. Increased bacterial populations were also expected to be positively correlated with aggregate stability. The external, more robust bacterial communities contribute to the formation and function of soil aggregation processes by increasing carbon sequestration, clay mineralization, and greater intra-aggregate porosities.

Influence of the forest-tundra ecotone and environmental variables on subalpine forest at Niwot Ridge, Colorado.

Date Presented: Saturday Night

Lead Author: Laura Mujica-Crapanzano
Co-Authors: Patrick BOURGERON, Hope HUMPHRIES
Institutional Affiliations: INSTAAR, University of Colorado at Boulder
Primary Site: NWT

Abstract: The forest-tundra ecotone (FTE) is the transition area between alpine tundra and subalpine forest (SAF) ecosystems. A major characteristic of FTEs is that they modify the flow of water and materials between the adjacent ecosystems. Our objective was to examine the influence of the spatial pattern and abundance of tree size/growth-form (S/GF) classes within the treeline and environmental variables (EVs) on the spatial pattern and abundance of trees in the SAF at Niwot Ridge, Colorado. At the landscape scale, we compared treeline vegetation among the three FTE types present at Niwot Ridge, and at the local scale we compared treeline and SAF vegetation. Spatial pattern analyses (Ripley’s K function and variance reduction bivariate estimate) were used to examine: (1) the spatial distributions of S/GF classes and (2) the spatial associations among S/GF classes. Direct ordination techniques were used to examine the relationship between EVs and the abundance of S/GF classes. At the landscape scale, the results suggest the following: (1) The spatial distributions of S/GF classes are, in general, significantly (P<0.05) different from random (clumped) at all distances. (2) Spatial associations among S/GF classes are generally not significant. (3) EVs explaining the greatest amount of variation in abundance among S/GF classes include elevation, metamorphic rocks, and skyward angle variability. (4) Ruggedness index variability best discriminates among the treeline sections of transects. At the local scale, the results suggest: (1) The spatial distributions of S/GF classes in the SAF are predominantly clumped at all distances. (2) Spatial associations among S/GF classes in the SAF are significantly different from spatial independence and exhibit different patterns of association from treeline vegetation. We conclude that the Niwot Ridge SAF is differentially influenced by treeline vegetation among FTE classes and by EV factors such as elevation, microtopography, and geology.

Integrated soil and vegetation monitoring system for grassland, shrubland and savanna ecosystems.

Date Presented: Friday Night

Lead Author: J. E. Herrick¹
Co-Authors: D. Toledo¹, J. VanZee¹, K. Havstad ¹, D. Pyke², P. Shaver³, M. Pellant⁴, A. Melagoza ⁵M. Remmenga⁶, R. Unnasch⁷
Institutional Affiliations: USDA ARS, Jornada Experimental Range¹, USGS, Corvallis, OR², NRCS, Corvallis OR³, BLM, Boise ID⁴, INIFAP, Chihuahua, Chihuahua Mexico⁵, New Mexico State University, Las Cruces NM⁶, The Natu
Primary Site: JRN

Abstract: Rangeland monitoring is frequently limited by high costs, low relevance to management and the lack of a sound scientific foundation. We describe a system that addresses these limitations by integrating short- and long-term field indicators based on basic and applied research at the Jornada LTER and other research stations in the western United States. This system uses simple soil and vegetation measurements of long-term changes in three attributes: soil and site stability, hydrologic function, and biotic integrity. These indicators have been correlated with more intensive measurements of current condition, degradation risk and recovery potential. Basic measurements used to monitor changes in the three attributes across most ecosystems include line-point intercept, a "gap"intercept and a field soil aggregate stability test. The gap intercept measurement is used to rapidly measure changes in the size and number of large gaps in the vegetation. The area covered by large gaps is a sensitive indicator of changes in the resistance to runoff, erosion and weed invasion. Additional measurements are included to address more specific management objectives and site-specific issues. A related set of short-term indicators are used to interpret long-term changes and to guide more frequent management adjustments. The poster includes a summary of a recently published manual that describes the protocols and an analysis of the relative costs, knowledge requirements and value of complementing the field data with currently available remote sensing technologies. It also includes recent calibration data relating indicators generated using the standard protocols with more traditional wildlife habitat indicators.

Integrating Science and Education at the Plum Island Ecosystem Long Term Ecological Research site.

Date Presented: Saturday Night

Lead Author: Elizabeth B. Duff
Co-Authors: Dr. Robert Buchsbaum, Dr. David Burdick, Susan Brown, Greg Chmura, Diane Cooper, John Halloran, Nancy Nicholson, Jenny Meyer
Institutional Affiliations: Massachusetts Audubon Society, Massachusetts Audubon Society, Jackson Estuarine Laboratory, Nock Middle School, Ipswich High School, Pine Grove School, Nock Middle School, Newbury Elemerntary School, Nock Middle School
Primary Site: PIE

Abstract: Since 1996, the Massachusetts Audubon Society has been carrying out a K-12 integrated science and education program with schools in the Plum Island Sound Ecosystem. Under guidance of Massachusetts Audubon, schools have set up their own transects to analyze vegetation changes over the long term and are also making measurements of porewater salinities and the fish community. Students have been engaged in research on the spread and impacts of invasive species, particularly Phragmites australis, in the salt marsh. Their studies are in parallel with those LTER and collaborating scientists. The goals of the project are to spark the students’ interest in field science and enhance their understanding of a local ecosystem, to develop and enhance a sense of stewardship in local citizens by connecting students to their natural environments, to create a regional network of students, teachers and professional scientists, and to provide teachers with support in teaching and meeting the goals of education reform. An attractive aspect of the project from the perspective of the teachers is that the students collect real data that are of value to the scientists studying the Plum Island Sound Ecosystem. The teachers are encouraged to integrate the framework of the salt marsh and the research into a number of related areas, such as creative writing, mathematics, and instructing the students in new technologies. Essential elements of the project are teacher trainings which instruct the teachers in the methodologies and provide opportunities for professional development, hands-on help in the field by Mass Audubon education staff, input by scientists particularly with data analysis, an annual conference where students share their results, a website, and program evaluation. A recent evaluation carried out by the School of Education at Lesley University reported that the program had positive impacts on the students, teachers, and the community.

Inter-annual variation in production across a dynamic coastal landscape

Date Presented: Saturday Night

Lead Author: Donald Young
Co-Authors: John Porter, Frank Day, Robert Christian
Institutional Affiliations: Virginia Commonwealth University, University of Virginia, Old Dominion University, East Carolina University
Primary Site: VCR

Abstract: Inter-annual variations in primary production were estimated for a ten-year period across the diverse landscape of the Virginia Coast Reserve to determine relationships among habitats and among species relative to potential environmental drivers. Habitats included dunes and swales on a barrier island and the high salt marsh on the mainland side of a coastal lagoon. This work synthesizes information in the context of our conceptual model that relates ecosystem state to the relative positions of land, sea and ground water surfaces. The habitats were compared with each other and environmental drivers, as were the dominant grasses, Ammophila breviligulata, Spartina patens, Distichlis spicata, and the dominant shrub, Myrica cerifera. For all habitats and species there were pronounced inter-annual variations in relative production (z-score) that appear to be related to the availability of freshwater. In most drought years, there were decreases in all relative production values. Spring conditions appear most critical with the strongest correlation to relative production being the Palmer Drought Index for May. All correlations among species and among habitats were positive, although often non-significant. Swale and high marsh habitats may be less sensitive to drought than dunes due to a closer proximity to freshwater. Among the species, variations were confounded by landscape position and specific physiological differences (e.g. C3 vs C4 photosynthesis). Variations in production are more complex than initially envisioned, but variations in regional climate do provide a signature on plant growth that transcends coastal landscape units.

Interaction of soil fertility and photosynthetic plasticity as a mechanism promoting plant invasion in wetlands

Date Presented: Friday Night

Lead Author: Heather Hager
Co-Authors: Jean Knops
Institutional Affiliations: University of Nebraska-Lincoln
Primary Site: CDR

Abstract: Wetland habitats have been subject to substantial increases in nutrient availability, caused by increasing agricultural runoff and nutrient deposition from atmospheric pollution. High eutrophication rates cause an increase in aboveground plant biomass, resulting in increased competition for light. We hypothesize that there is a trade-off between high nitrogen use efficiency (requiring a long life span) and the ability of plants to reposition leaves in the high light environment of the upper canopy. Secondly, we hypothesize that eutrophication promotes invasions by favouring a subset of plant species that are highly plastic (both photosynthetically and morphologically), allowing them to capture more light, increase levels of net primary productivity and outcompete other species that are less plastic and cannot increase their productivity levels to the same extent. Our comparison of morphological and physiological photosynthetic characteristics for a suite of invasive and non-invasive wetland plants shows that the invasive plants abscise lower canopy leaves as new leaves with high photosynthetic rates develop in the upper canopy, whereas the native species alter the physiology of their lower canopy leaves so that they are shade-adapted, with lower maximum photosynthetic rates. We plan to manipulate nutrient availability in wetlands to test its effect on the photosynthetic plasticity of invasive and non-invasive species and determine whether eutrophication contributes to increased wetland invasion.

Internal wave effects on phytoplankton primary production: Results of in situ experiments vs. modeling

Date Presented: Friday Night

Lead Author: Mary Anne Evans
Primary Site: ARC

Abstract: Internal waves may play an important roll in controlling the light exposure of phytoplankton. This could effect the primary production of light limited phytoplankton, however such dynamics are not captured by standard primary production measurements. As these internal waves often occur at same depths as a subsurface chlorophyll maximum in arctic lakes they could contribute to the over all productivity of the lake. To further understand the phytoplankton primary production of arctic lakes I have studied the importance of internal waves to phytoplankton primary production using concurrent modeling and experimentation. I have modeled phytoplankton primary productionfor different depth x movement treatments using: P-I curves, surface light measurements, and light extinction measured at Toolik Lake. For the day from which the modeling parameters were taken I have performed in situ measurements of PP on fixed depth and moving phytoplankton samples. There experiments were conducted in Toolik Lake, Alaska USA. Internal waves in Toolik Lake can have amplitudes of 2+ m and range in period from ~2-24 h (S. MacIntyre, personal communication). Moving samples in both the model and in situ experiments had an amplitude of 1.5 m and a period of 4 h. In situ experiments show a doubling in phytoplankton primary production in moving vs. fixed depth incubations at depths where internal waves occur. Current modeling results greatly underestimate the effect of movement on primary production as compared to the experimental results. The inconsistency of in situ vs. modeling results indicated the need to include additional parameters in the model. I am currently investigating the inclusion of temperature and the effects of prior light exposure in modeling this system.

International Contributions to the McMurdo Dry Valleys Long Term Ecological Research (MCM-LTER) Program

Date Presented: Saturday Night

Lead Author: Ian Hawes
Co-Authors: Johanna Laybourn Parry, Martyn Tranter, Emily Roberts, William Marshall
Institutional Affiliations: NIWA, NZ, University of Nottingham, University of Bristol
Primary Site: MCM

Abstract: In the eleven years of MCM-LTER’s existence, a number of international scientists have contributed to the science effort making important contributions to the understanding of ecological and biogeochemical dynamics of the McMurdo Dry Valleys, Antarctica. Currently there are three major scientific activities at MCM-LTER led by international scientists: the investigation of microbial mats in the closed-basin and perennially ice-covered lakes, the study of mixotrophy and microbial loop dynamics in these lakes, and the biogeochemistry of cryoconite holes on the surfaces of the glaciers in Taylor Valley. These three activities are outlined here. These investigations have added important information to our understanding of the MCM ecosystem that could not have been gathered by MCM-LTER scientists alone. Important highlights of this work are 1) in some lakes (i.e. Lake Hoare) 50% of the primary production takes place in the benthic mats, 2) mixotrophy is probably a major survival strategy for cryptophytes in the Taylor Valley lakes, and 3) distinct ecosystems exist in the glacier surfaces and these cryoconite holes are unique in that they have ice lids that may stay closed keeping the ecosystem isolated from the atmosphere for decades.

International LTER Strategies, Challenges and Opportunities

Date Presented: Friday Night

Lead Author: Alan Schroeder
Primary Site: INT

Abstract: Global LTER collaboration is undergoing rapid change. To meet this challenge, the Network office (NET) is undertaking analyses to better understand the dynamics of ILTER structures and interactions, and to target opportunities for enhancement and improvement. Analyses include new country commitments, leadership, strategic sites, management strategies, research themes and thrusts, websites, databases, collaboration, fund leveraging and developing liaisons. These analyses will be presented to increase the awareness and understanding of key issues among ILTER partners, and to help plan for the future. Opportunities and strategies for increased collaboration, fund leveraging, exposure, reach and influence of ILTER are presented.

Investigating multiple spatial scales of Phoenix’s urban forest

Date Presented: Friday Night

Lead Author: Jason Walker
Co-Authors: John Briggs
Institutional Affiliations: Arizona State University
Primary Site: CAP

Abstract: Cities by their nature are hierarchical. Urban areas can be considered spatially nested hierarchies, a complex system composed of interacting subsystems, which in turn are composed of smaller subsystems. These highly interacting systems form the foundation of ecological patchiness. We propose a multiple-scale, spatial investigation of metropolitan Phoenix’s urban forest structure to investigate vegetative patchiness. The urban forest is being analyzed using fine resolution (0.3 m) aerial photographs to identify individual tree cover and stand density. Ground sampling is providing local scale species diversity information as well as ground-truthing information. Remote sensing will be evaluated in order to increase the spatial extent. Once data is gathered and synthesized, it will form the basis to analyze ecological processes. Currently, we have plotted over 25 km of local scale patterns of urban forest structure. From this sample, we have isolated vegetation occurring in residential neighborhoods and calculated simple regression analysis with multiple variables of census data at the block group level. Preliminary results indicate significant social factors that potentially affect urban forest structure within residences to be: age of neighborhood, percentage of occupancy, and income.

Jornada Basin LTER: overview and synthesis

Date Presented: Friday Night

Lead Author: Debra Peters¹
Co-Authors: Laura Huenneke², Brandon Bestelmeyer¹, Dale Gillette³, Vince Gutschick⁴, Kris Havstad¹, Jeff Herrick¹, Dave Lightfoot⁵, Curtis Monger⁴, Tony Parsons⁶, Al Ra
Institutional Affiliations: USDA ARS, Jornada Experimental Range¹, Northern Arizona University², NOAA³, New Mexico State University⁴, University of New Mexico⁵, University of Leicester⁶, Duke University⁷, K
Primary Site: JRN

Abstract: Chihuahuan Desert landscapes exemplify the ecological conditions, vulnerability, and management issues found in semiarid and arid regions around the globe. The goal of the Jornada Basin LTER program is to identify the key factors controlling ecosystem dynamics in these landscapes with the objective of understanding the causes and consequences of desertification. Previous LTER work focused primarily on the scale of a single plant-interspace and on the redistribution of soil resources at that scale. However, the intrinsic nature of arid and semi-arid regions, including the prevalence of high winds and short intense precipitation events in landscapes with substantial topographic variability, promotes the redistribution of materials (water, soil particles, nutrients, seeds) at larger scales. Our central hypothesis is that landscape position and linkages among landscape units exert important influences on ecosystem dynamics and biotic patterns within sites. We are combining short- and long-term experiments, observations, remotely sensed images and aerial photos with geographic information systems and simulation models to assess controls on fluxes and patterns across a range of spatial and temporal scales. We are also using cross-site studies to test the generality of our hypotheses for application to management and remediation of semi-arid ecosystems and desertified landscapes.

Jornada Basin Schoolyard LTER: Hands-on Science Education In the Chihuahuan Desert

Date Presented: Friday Night

Lead Author: Stephanie Bestelmeyer
Primary Site: JRN

Abstract: Each year, the Jornada Basin SLTER program reaches more than 5,000 kindergarten through 12th grade (K-12) students and 200 K-12 teachers with hands-on, inquiry-based science education. The key to this volume of outreach is a unique partnership that has been established between the Jornada Basin LTER, the USDA-Agricultural Research Service Jornada Experimental Range, and the Chihuahuan Desert Nature Park, a nonprofit science education organization. Using the combined expertise and energy of these partners, we have created a multifaceted K-12 education program which includes schoolyard vegetation study sites, field trips, classroom presentations, and teacher workshops. Recently, we have also created new long-term, data collection modules on weather, microclimates, soil, arthropods, and birds. These modules are designed to be feasible in any schoolyard, thus marking an exciting new direction for the Jornada Basin Schoolyard LTER program.

JOURNEY TO EL YUNQUE: A MODELING APPROACH TO LUQ LTER EDUCATIONAL OUTREACH

Date Presented: Saturday Night

Lead Author: Steven McGee
Co-Authors: J. Zimmerman, S. Croft
Institutional Affiliations: Wheeling Jesuit University, University of Puerto Rico
Primary Site: LUQ

Abstract: Educational researchers at the Center for Educational Technologies, Wheeling Jesuit University, are working with Luquillo LTER researchers to develop the Journey to El Yunque Web site for middle-school life science students. The primary goal of the Web site is to use the case study of El Yunque LTER research to improve students' understanding of ecology and changing ecosystems. Students will investigate a core LUQ LTER research question, namely, "Organisms in El Yunque seem to be well-adapted to natural disturbances, but will they be able to cope with changing land uses and changing climate, such as the predicted increase in frequency and strength of hurricanes?" Students will investigate this question by examining datasets of population dynamics for key rainforest species, including, decomposers (fungi, snails), producers (tabonuco, yagrumo), herbivores (walking sticks, caterpillars), and insectivores (coquí, anole). The students will manipulate model parameters related to limiting factors to gain an understanding of how the limiting factors affect population dynamics. The activity will culminate in students manipulate a model that demonstrates the effects of hurricanes on a subset of the El Yunque food web that includes one decomposer, one producer, one herbivore, and one insectivore.

K-12 Education Activities and Research at the Shortgrass Steppe LTER

Date Presented: Saturday Night

Lead Author: John C. Moore
Co-Authors: Howard Horton, Meghan Quirk
Institutional Affiliations: Department of Biological Sciences and The Math and Science Teaching Insititute, University of Northern Colorado
Primary Site: SGS

Abstract: The Shortgrass Steppe (SGS) LTER has developed a diverse array of K-12 Educational and research activities by coordinating LTER research and schoolyard supplements with established and new K-12 education programs. The SGS-LTER activities are coordinated through the Math and Science Teaching (MAST) Institute at the University of Northern Colorado, and draws on the expertise of faculty from science and mathematics education, LTER content areas, and educational psychology. Major themes include providing K-12 teachers and high school students with research opportunities, teacher professional development workshops that cover ecological concepts and field protocols that can be transferred to the classroom, curriculum development that incorporates long term data collection and monitoring; and research on effectiveness of different mentoring strategies, student understanding and attitudes about ecology, and extent and nature of the achievement gap and representation of minorities and whites in STEM assessments and disciplines, respectively. The presentation focuses on the nature of the collaborations, the sources and mechanisms for funding the activities, the outcomes of our research in education, mentoring and the gaps in achievement and participation by different segments of the population.

K-8 Tallgrass Prairie Activities and Education Facilitated by the Cedar Creek Schoolyard Program.

Date Presented: Friday Night

Lead Author: Anne Reich
Co-Authors: Susan Barrott
Institutional Affiliations:

Abstract: The Cedar Creek Schoolyard LTER program aims to combine scientific research and science education. The purpose is to help students and teachers become more informed about ecological processes via hands-on involvement in long-term research. Cedar Creek Schoolyard LTER has been working with two public schools in the White Bear Lake Area Schools District: Centerpoint Elementary School (240 students) and Sunrise Park Middle School (1,100 students). Both schools have prairies planted on site. In 1999, the Schoolyard LTER began working with Centerpoint teachers to help them think “long term ecological research” when planning activities. We have developed simple projects and protocols to enable teachers and their students to gather data that will provide long term ecological information about the dynamics of the prairie. Planted in 2000, the Sunrise Prairie Project is modeled after a real-life biodiversity experiment at Cedar Creek LTER. The Sunrise experiment has study plots with differing numbers and species of native prairie plants. Research is designed to help students make observations and gather data to answer questions about biodiversity, plant functional groups, productivity, soil chemistry, plant-insect interactions, phenology, and more. The use of the prairie sites, and the data collected, is integrated into classroom curriculums including: math, chemistry, biology, ecology, history, geography and art.

Lake Fryxell Food Web

Date Presented: Saturday Night

Lead Author: Kerry McKenna
Co-Authors: D. Moorhead, J. Laybourn-Parry
Institutional Affiliations: Department of Earth, Ecological and Environmental Sciences University of Toledo, Institute of Environmental Sciences University of Nottingham
Primary Site: MCM

Abstract: A general model has been developed for examining energy flow in Lake Fryxell one of the McMurdo Dry valley lakes. Data from the 1996 and 1997 seasons were used to calculate flows of biomass, predation, respiration (basal metabolic and production-associated), and egestion for 7 trophic groups. We have been able to simulate basal respiration that closely matches field observations of community respiration, as measured by the ETS method (R²=0.66). However when total respiration (basal respiration + respiration due to production) is compared to these field measures a similar linear relationship is found but estimates are an order of magnitude higher than observed. This leads us to conclude that the standard allometric equation, for basal metabolic respiration may not be appropriate for describing energy flow in this system. Earlier studies suggesting much lower than expected relationships between biomass and respiration for these Antarctic organisms are needed to approximate field observations.

Land Use and Neighborhood Change in the Gwynns Falls Watershed: An Analysis of Green Space

Date Presented: Friday Night

Lead Author: Molly Michaud
Co-Authors: Morgan Grove, Austin Troy
Institutional Affiliations: University of Vermont
Primary Site: BES

Abstract: Maryland has become well-known for its progressive efforts to implement Smart Growth policies, from programs that protect large tracts of rural land to those that acquire and rehabilitate urban parks. Critics of sprawl and proponents of livable cities have sought to promote, among other things, a mixture of land use that includes more green spaces in the form of trees, parks, and open space. As the push to conserve more lands continues, it becomes meaningful to understand the long-term dynamics between these land uses and adjacent neighborhoods. Specifically we ask if parks and open spaces are related to neighborhood stability, in other words, long-term sustainability or resilience to change. The Gwynns Falls watershed serves as a study site to perform a longitudinal examination of neighborhoods and the impacts of green space. In particular, we ask, “Is there a correlation between green spaces and neighborhood stability and do protected lands have the same neighborhood effect as unprotected lands?”

Land use and the changing reactivity of organic nitrogen and phosphorus exported from urban watersheds

Date Presented: Friday Night

Lead Author: Sujay S. Kaushal
Co-Authors: Peter M. Groffman, Stuart E.G. Findlay, and David T. Fischer
Institutional Affiliations: Institute of Ecosystem Studies
Primary Site: BES

Abstract: Organic N and P can comprise a substantial proportion of the total N and P present in undisturbed and disturbed streams. Yet, relatively little is known about the ecological significance of these organic forms. Changes in the amount and biological reactivity of organic N and P were investigated in streams of the Gwynn’s Falls watershed along a gradient of land use. Concentrations of inorganic N and P declined from suburbanized and agricultural headwaters to urbanized reaches further downstream. In contrast, concentrations of organic N and P increased along the river network and comprised 53% and 71% of the total N and P exported to Chesapeake Bay. The biological reactivity of organic C, N, and P varied with land use and season. Across sites, 0-47% of organic carbon, 0-41% of organic nitrogen, and 0-58% of organic P were biologically available over time scales of 2-3 days. Measurements of bacterial production and respiration efficiency suggested that the growth and metabolism of microbes in urban streams were less affected by organic matter quality and limitation by inorganic nutrients as compared to forested reference streams. Reactive fractions of organic N and P may accumulate along suburban and urban drainages. Although not typically quantified, these fractions have the potential to be an important supply of nutrients, particularly to coastal ecosystems experiencing rapid changes in land use.

Land-atmosphere interactions at the Shortgrass Steppe LTER

Date Presented: Saturday Night

Lead Author: Adriana Beltran-Przekurat ¹
Co-Authors: Roger Pielke Sr. ¹, Michael Coughenour², Indy Burke ³ and Jack Morgan ⁴
Institutional Affiliations: ¹ Department of Atmospheric Science, Colorado State University (CSU), ² Natural Resources Ecology Lab, CSU, ³ Department of Forest, rangeland and watershed stewarship, CSU, ⁴ USDA-ARS
Primary Site: SGS

Abstract: Observations and modeling results have shown that land use practices effect regional climate in the Shortgrass Steppe (SGS) region through their influence on energy partitioning and balance. A coupled atmospheric-vegetation model constitutes an appropiate tool to study the interactions and feedbacks between the vegetation, soil and the atmosphere. Disturbances such as domestic livestock grazing, cultivation and irrigation practices alter the seasonal dynamics of the energy balance, and influence the local and regional temperature and precipitation patterns. The Regional Atmospheric Modeling System (RAMS) coupled with a plant-scale model GEMTM (the coupled system is referred to as GEMRAMS) is used to quantify the impact fo these land use practices on messoscale climatic patterns at the SGS site. Measurements from individual landscape units and from the Bowen ratio towers (i.e CO2 and water fluxes) will be used to validate the performance of the coupled modeling system GEMRAMS.

Landscape Influences on Aluminum and Dissolved Organic Carbon in Streams draining the Hubbard Brook Valley

Date Presented: Friday Night

Lead Author: Sheila Palmer
Co-Authors: Brian I. Wellington, Chris E. Johnson and Charles T. Driscoll
Institutional Affiliations: Syracuse University
Primary Site: HBR

Abstract: Concentrations of both aluminum (Al) and dissolved organic carbon (DOC) in stream waters are likely to be regulated by factors that influence water flowpaths and residence times, and by the nature of the soil horizons through which waters flow. In order to investigate landscape-scale spatial patterns in streamwater Al and DOC, we sampled 7 streams draining the Hubbard Brook valley in central New Hampshire. We observed considerable variation in stream chemistry both within and between headwater watersheds. Across the valley, concentrations of total monomeric aluminum (Alm) ranged from below detection limits (<0.7 umol/L) to 22.3 umol/L. In general, concentrations of Alm decreased as pH increased downslope. There was a strong relationship between organic monomeric aluminum (Alo) and DOC concentrations (R2 = 0.92), highlighting the importance of DOC in regulating the speciation of Al. We observed the highest Alm concentrations in: i) a watershed characterized by a steep narrow drainage basin and shallow soils, and ii) a watershed characterized by exceptionally deep forest floor soils and high concentrations of DOC. Forest floor depth and drainage area together explained much of the variation in lnAlm (R2 = 0.79) and lnDOC (0.87). Linear regression models were moderately successful in predicting Alm and DOC in streams that were not included in model building. We predicted the lnDOC in streams to within a range of –19 to +6% of observed concentrations, and lnAlm within –23 to +26%. However, when back-transformed, predicted DOC concentrations were as much as 72% adrift from observed DOC concentrations and Alm were up to 49% off. This geographic approach to modeling Al and DOC is useful for general prediction, but for more detailed predictions, process-level biogeochemical models are required.

Landscape Scale Patterns of Nutrient Use Efficiency with in Cladium jamaicense in the Florida Everglades

Date Presented: Friday Night

Lead Author: Mike Right
Co-Authors: Dan Childers
Institutional Affiliations: Florida International University
Primary Site: FCE

Abstract: Changes in freshwater flow and nutrient enrichment have affected nutrient and organic matter input to the Everglades (Turner et al., 1999). The aforementioned changes have had a direct impact on the flora and fauna of the marsh ecosystem. It has been shown that plants located in eutrophic areas are less efficient at reabsorbing nutrients than those found in oligotrophic areas (Strachurski & Zimka 1975). Cladium jamaicense (sawgrass) was studied at sites which were found in close proximity to canal inflows and others that were located down marsh from canal inputs. There was no significant difference in reabsorbtion efficiency based on site location. This research was conducted at sites located throughout the southern Everglades allowing an accurate conclusion to be drawn about nutrient efficiency changes in sawgrass over a wide geographic spectrum. We observed the nutrient use efficiency of phosphorus (PUE) and nitrogen (NUE) in C. jamaicense; which is the predominate macrophyte found throughout the Everglades. Due to the dramatic differences (almost double) in nutrient use efficiency it was evident that sawgrass is limited by phosphorus and not nitrogen.

Lasting Effects of Hurricane Damage on Long-Term Forest Development at the Harvard Forest LTER

Date Presented: Friday Night

Lead Author: Kristin Wilson
Co-Authors: Audrey Barker Plotkin, David Foster
Institutional Affiliations: Harvard Forest, Harvard University
Primary Site: HFR

Abstract: Central to the Harvard Forest LTER is examination of natural disturbance and anthropogenic stress. Hurricane blowdown is a major natural disturbance process in New England, and has been studied at Harvard Forest through large-scale manipulation, historical reconstruction and modeling. Permanent plot data allow us to expand our understanding of long-term hurricane effects on forest dynamics; here we use permanent plot data to illustrate the persistent effects of hurricane damage 30-60 years after the great hurricane of 1938. A 2.9 hectare hardwood forest plot was established in 1969 at Harvard Forest. All living and dead trees were censused in 1969, 1975, 1987-92 and 2001. Based on distribution of windthrown stems and damage boundaries delineated immediately after the 1938 hurricane, the site was divided into severe (91-100% damage, 0.3 ha), moderate (51-75% damage, 0.9 ha) and low (11-25% damage, 1.7 ha) damage areas. Stand development followed different trajectories in the severe area versus the low and moderate areas. Stem density was higher and decreased more rapidly over time, basal area was lower, and average tree size was smaller in the severe area, indicating a stand in an earlier phase of stand development. Quercus rubra and Acer rubrum were the dominant species across the site, but Q. rubra was more important in the low and moderate damage areas, whereas A. rubrum and Betula species were more important in the severe area. The different damage areas did not converge over time; B. lenta and B. alleghaniensis became more important in the severe area over time, whereas a growing number of later-successional species (Fagus grandifolia, Tsuga canadensis and Acer saccharum) recruited into the low and moderate areas. This study shows that forest recovery following hurricane disturbance is a gradual process extending beyond the timeframe of most studies and allows for a better understanding of the long-term role of hurricane disturbance in the New England landscape.

Linking Biogeochemistry with Microbial Diversity and Function in the McMurdo Dry Valleys, Antarctica

Date Presented: Saturday Night

Lead Author: Jill A. Mikucki
Co-Authors: Christine F. Foreman, Brent C. Christner, and John C. Priscu
Institutional Affiliations: Montana State University
Primary Site: MCM

Abstract: The unique physical and chemical conditions of the McMurdo Dry Valleys are driven largely by climate, solar cycle, and geological evolution. The resultant ecosystem is characterized by wide-ranging chemical and physical extremes of salinity, metal concentration, inorganic carbon, freeze-thaw cycles and light-dark periods that challenge the ingenuity and plasticity of life. The geochemistries and physical constraints of this polar desert are reflected in the diversity and metabolic traits of the microbial assemblages present. As such, the inhabitants require strategies to endure desiccation, nutrient deprivation, and tolerance to extreme cold and freezing. In situ biogeochemical measurements and culture-based techniques, have been used in concert with molecular analysis to describe and characterize the role of microorganisms associated with the McMurdo Dry Valley glaciers and lakes. Preliminary results imply that the distinctive habitats of this polar desert promote disparate metabolic strategies and innovative tactics for survival in extreme cold.

Linking Temporal Variation in Bacterial Community Structure with Ecosystem Properties in a Temperate Estuarine Complex

Date Presented: Saturday Night

Lead Author: Linda Blum
Co-Authors: Mike Lowit
Institutional Affiliations: University of Virginia
Primary Site: VCR

Abstract: DNA cross-hybridization was used to determine genetic compositional similarity and relative diversity of whole-community DNA extracts of bacteria from two estuarine systems. Mid-estuary samples were collected at one-month intervals over 24 consecutive months. Relationships between community structure, environment (12 variables), and time (autocorrelation) were examined. Mantel tests, used to compare the three datasets, revealed a significant relationship between compositional and environmental similarity ? independent of common temporal structuring (partial Mantel) in one creek, but not the other. Cluster analyses of the compositional similarity matrices show three to four distinct groups: similar in both creeks and depicting short-term autocorrelation with annual reproducibility. Multivariate discriminant analysis showed that water temperature and organic matter are the most important contributing variables for explaining these community groups. Ranking of samples using relative diversity relationships shows diversity minima occurred in spring and fall, diversity increasing through time in summer and winter months respectively. Communities from the two systems remained dissimilar (<30% similarity) over the entire study. Overall, these results suggest that temporal variations in bacterial community structure (at the observed scale) are primarily a function of climatically driven seasonal environmental shifts, the temporal pattern and trajectory of compositional variations being independent of the local composition.

Long term dynamics of a degraded arid shrub-land: delayed responses and the importance of spatial processes

Date Presented: Friday Night

Lead Author: K.M. Havstad¹
Co-Authors: D.P. C. Peters¹ and L. Murray²
Institutional Affiliations: USDA ARS, Jornada Experimental Range¹, New Mexico State University²
Primary Site: JRN

Abstract: In arid environments, vegetation dynamics are often unpredictable, nonlinear, and strongly influenced by environmental and anthropomorphic drivers. Conversely, vegetation states are often quite stable over time, and without intensive inputs, degraded conditions may persist for decades despite removal of agents of degradation. In addition, arid landscapes are spatially heterogeneous in edaphic factors and vegetation characteristics such as seed source following disturbance. Characterizing vegetation dynamics in response to management practices in arid environments requires long term experiments that capture important temporal influences of infrequent, episodic events and an understanding of spatial influences across the landscape on those dynamics. In 1938, an experiment was designed at the Jornada LTER to examine the effects of shrub removal on perennial grasses in a site dominated by creosotebush. All plots were resampled in 1947, 1960, 1967, and 2001. The shrub clearing treatment has been reapplied immediately following each sampling date. In 2002-2003, a 17 ha area around the site was ground surveyed for location and distribution of black grama plants that serve as seed sources to the removal plots. Our results show a delayed response by black grama following shrub removal that was accentuated by the drought of the mid 1950’s. A low density of black grama plans in the surrounding area likely contributes to this slow recovery. Thus, in this arid system, we need to consider not only the acute extreme disturbance, but also the climatic variability and spatial context of the land area disturbed.

Long Term Ecological Research at the Valles Caldera National Preserve in Northern New Mexico.

Date Presented: Saturday Night

Lead Author: Robert Parmenter
Primary Site: SEV

Abstract: The Valles Caldera National Preserve (VCNP), a 40,000 ha preserve established by Congress in 2000, has recently begun a long-term scientific research program in ecology, geology and anthropology for the purposes of (1) understanding the ecology of the VCNP landscape, (2) providing detailed databases for resource management decisions, and (3) developing a science education/public outreach program in northern New Mexico. Located in a 1.2 million year old volcanic caldera, the VCNP ranges in elevation from 2,590 to 3,430 m (8,500 – 11,250 ft), and contains extensive regions of montane grasslands and mixed conifer forests. The caldera includes the headwaters of two major watersheds that contribute to the Jemez River (a tributary of the Rio Grande). Current research activities include population studies on vertebrates and invertebrates (both terrestrial and aquatic), experimental exclosure studies for both elk and livestock impacts, NPP and animal herbivory studies, stream chemistry studies, and impact studies in forests from fire and mechanical thinning. Details of the VCNP resources and infrastructure are described, along with potential future studies in collaboration with LTER programs.

Long Term Measurement at the Hubbard Brook Experimental Forest

Date Presented: Friday Night

Lead Author: Hubbard Brook Cooperators

Abstract: The Hubbard Brook Experimental Forest (HBEF) was established as a center for hydrologic research in 1955. The study was expanded in 1963 with the Hubbard Brook Ecosystem Study (HBES) to investigate hydrologic-elemental cycle interactions under different conditions of disturbance. The HBEF is a 3,037 ha forest of northern hardwoods, with spruce and fir at higher elevations. A strength of the HBES and the Hubbard Brook LTER is our program of long-term measurements. These measurements show that short-term observations are often misleading and that decades may be required to detect real changes in complex ecosystems. Long-term measurements at the HBEF provides: 1) insight into ecosystem function, 2) empirical data for testing models and generating hypotheses, 3) a record of extreme or unusual events and 4) information that is relevant to regional, national and global issues. In this poster we provide some examples of long-term measurements at the HBEF.

Long-Term climate control of radial growth of boreal trees: the last 200 years and the next 100 years

Date Presented: Friday Night

Lead Author: Valerie A. Barber
Co-Authors: Glenn P. Juday
Institutional Affiliations: University of Alaska Fairbanks
Primary Site: BNZ

Abstract: Although boreal tree growth sometimes increases with climate warming and treeline is advancing in some regions, recent studies at Bonanza Creek LTER and elsewhere show that the negative effects of warming on the boreal forest can be greater than the positive effects. Ninety-five percent of the Alaska boreal forest consists of three species of trees (black spruce 55%, white spruce 25%, and birch 14%) and we have found evidence of decreased radial growth from warming temperatures in all three species of trees on at least some sites. Hundreds of tree disks and cores have been collected from each species to determine climate sensitivity. All sites sampled to date register some form of climate sensitivity from at least some trees and relationships are statistically significant so that predictive empirical relationships of climate on tree growth can be developed for most sites. Interior upland white spruce trees are all consistent in their negative growth response to warming temperature, while black spruce and birch show some mixed sensitivity. The recent find of a high level of climate sensitivity in black spruce in Alaska, along with a number of different climate indices which optimize growth is surprising and indicates that black spruce trees occupy sites with more varied environmental conditions than previously thought. Preliminary studies of Alaska birch show that it too responds to climate depending on site, and although different climate indices optimize growth according to site, summer temperatures appear to have the greatest affect. Future growth of these boreal tree species, derived from these empirical relationships with past temperature, has been developed for 5 GCM scenarios. The models produce climates indicating that some populations of at least two of the tree species would not survive, because rates of growth would approach zero within 70-100 years. These findings have broad implications for carbon uptake and aboveground carbon storage.

Long-Term Ecological Resarch (ILTER) Towards Sustainable Land Use and Biodiversity in a Mosaic of Agriculture and Tropical Forest in Costa Rica

Date Presented: Friday Night

Lead Author: Bruce Haines
Co-Authors: Chris Peterson
Institutional Affiliations: University of Georgia., Athens, Ga. 30602. USA
Primary Site: CWT

Abstract: The human population is rapidly growing but the size of planet earth remains the same, thus material resources to support each additional person continue to decrease. Local die back of human populations is a repeated theme in our history. How many human civilizations have survived intact for 1000 years? Are we managing the human and life support resources for sustainable quality of life? What alternative spatial arrangements of land uses might facilitate sustainability? Long-Term, Ecological Research, integrating physical, ecological, economic and social science facilitates ecological forecasting. We are developing a conceptual package of field measurements, remote sensing and model simulations that will enable resource managers to explore spatially explicit alternative resource uses that may enhance sustainability. Here we describe our multi-phased long-term research goals and our Phase I findings. In Phase I we are determining how long it takes to convert from abandoned cattle pasture back to forest and what are the controls to this forest regeneration. From our studies (1996 to 2002) we conclude that seed dispersal is the main limitation. Our general approach when coupled with knowledge of human economics and sociology can provide a valuable outreach program to help local decision makers balance their population size with resources to provide sustainable quality of life and sustainable civilizations for their descendants.

Long-term ecosystem education through the Kellogg Biological Station’s K12 Partnership for Science Literacy

Date Presented: Saturday Night

Lead Author: Glenn Green and Tim Parshal
Primary Site: KBS

Abstract: The Kellogg Biological Station’s Partnership for Science Literacy is collaboration between K12 science teachers in southwestern Michigan and research scientists and educators from Michigan State University. All participants are involved in the partnership over the course of three years with the understanding that educational reform is a long-term endeavor. Seventy teachers from 15 rural school districts attend workshops and summer institutes and meet regularly with advanced ecology Ph.D. students with the goal of improving science classroom instruction and teacher understanding of science content. The science is rooted in ecosystem ecology, based directly on five research areas studied by Long Term Ecological Research sites: primary productivity, decomposition, populations and trophic levels, nutrient cycling, and disturbances. This ecosystem framework is used to connect science concepts across disciplines and to link science teaching to ongoing scientific research. After two years, our approach has facilitated the most change in teacher understanding of science content and classroom teaching practice. In our first set of week-long summer institutes, teachers engaged in scientific study of local ecosystems and developed individual research projects in order to acquire a firsthand understanding of science inquiry. The ecological study and research project helped teachers develop instructional units to implement in their classrooms during the coming school year. Most teachers implemented their instructional units, oftentimes with critical assistance from ecology Ph.D. students. The school year workshops serve to introduce and reinforce ecosystem concepts and further explore inquiry-based science, assessment, and components of teaching for understanding.

Long-term impacts of non-native decapods on fish community composition, recruitment, and survivorship

Date Presented: Saturday Night

Lead Author: Theodore Willis
Co-Authors: John Magnuson
Institutional Affiliations: University of Wisconsin, North Temperate Lakes
Primary Site: NTL

Abstract: Orconectes rusticus in a well-known decapod invader in North Central North America. We used the North Temperate Lakes-LTER fish data to juxtapose the impact of crayfish abundance and identity on fish recruitment and the fish community. We focused on three mesotrophic lakes: Trout Lake, Big Muskellunge Lake, and Allequash Lake. All three lakes contained O. virilis as the native crayfish, and were invaded by O. propinquus prior to 1970. In addition, O. rusticus were detected in Trout Lake in 1978. Based on prior research we hypothesized that O. rusticus would be detrimental to fishes and O. propinquus would have little impact. Crayfish populations grew over time in Big Muskellunge Lake and Trout Lake, but remained at low levels in Allequash Lake. Multivariate analysis of fish communities in the three lakes showed that the Trout and Big Muskellunge fish communities were more variable than the Allequash fish community. In particular benthic fishes had become less abundant through time, and predatory fishes more abundant. Although O. propinquus abundance was lower than O. rusticus abundance, O. propinquus appeared to be affecting the Big Muskellunge fish community in fashions similar to what was seen in Trout Lake. Temporal dynamics of recruitment and year class formation of several species were correlated with crayfish abundance in Trout Lake. Recruitment in Big Muskellunge Lake appeared unaffected by crayfish, except for some centrarchid species. There was no apparent relationship between crayfish and recruitment in Allequash Lake. We concluded that the community and population effects of crayfish might be as dependent upon crayfish abundance as crayfish identity. Although Trout Lake and Big Muskellunge Lake contain different species, it appears that above a “threshold” abundance both species affect fish populations and fish communities similarly.

Long-term Manipulation of Rainfall and Temperature in Mesic Grassland: The RaMPs Facility at Konza Prairie

Date Presented: Saturday Night

Lead Author: Alan Knapp
Co-Authors: John M. Blair, Phillip A. Fay, Jonathan D. Carlisle, Scott L. Collins and Melinda D. Smith
Institutional Affiliations: Kansas State University, University of Minnesota - Duluth, University of New Mexico, National Center for Ecological Analysis and Synthesis
Primary Site: KNZ

Abstract: Temperature and precipitation are important climatic forcing functions for grasslands, making them vulnerable to projected climate changes. For the Central US, temperatures are expected to increase and rainfall patterns are predicted to become more extreme, with an increased frequency of large rainfall events and extended inter-rainfall droughts. We are addressing these two important aspects of climate change, and their interactions, with long-term research conducted in a unique experimental facility -- the Rainfall Manipulation Plots (RaMPs) at Konza Prairie. For 6 years, we have documented the impacts of altered rainfall patterns (larger rain events with longer inter-rainfall droughts, but no change in total precipitation) in replicated, grassland plots. A central hypothesis underpinning this experiment is that altered rainfall patterns will significantly affect temporal patterns and depth distributions of soil moisture and, thus, plant, community and ecosystem processes. In 2003 we added a warming treatment to assess the interactive consequences of multiple climate change factors. Results to date indicate that more extreme rainfall patterns reduced average soil water content in shallow (0-30 cm) soil layers, but increased temporal variability. Consequently, ANPP and soil CO2 flux were reduced, whereas plant species diversity, C3:C4 cover, and nitrate availability all increased with more variable rainfall inputs. Productivity of the sub-dominant grasses was more responsive to altered rainfall patterns than the dominant C4 grass, Andropogon gerardii. Combined effects of more extreme rainfall patterns and warmer temperatures are predicted to be additive, but more complex responses have emerged initially. Additional studies will determine if increased opportunities for invasion by exotic species with climate change. Our long-term goal is to identify trajectories, and potential non-linear stages, in community and ecosystem responses to these predicted climate changes.

Long-Term Nitrogen Dynamics of Coweeta Forested Watersheds in the Southeastern USA.

Date Presented: Friday Night

Lead Author: Bruce Haines (presenter)
Co-Authors: Wayne T. Swank ¹, Jim Vose¹, and Bruce Haines²
Institutional Affiliations: ¹Coweeta Hydrologic Laboratory, Southern Research Station, USDA Forest Service, Otto, NC and ² The University of Georgia, Athens, GA
Primary Site: CWT

Abstract: Long term data (25-30 years) were analyzed for trends and dynamics of NO3^-1 and NH4⁺¹ deposition and loss for mature mixed hardwood forest stands. Watershed N saturation was evaluated in the context of altered N cycles and stream inorganic N responses associated with management practices (cutting prescriptions, species replacement and prescribed burning) and with natural disturbances (drought and wet years, insect infestation, hurricane damage, and ozone episodes). Reference watersheds were highly retentive of inorganic N with deposition of < 6.7 kg ha^-1 yr ^-1 and stream water exports below 0.25 kg ha^-1 yr ^-1. Reference watersheds were in transition between stage 0 and stage 1 of watershed N saturation as evidenced by significant time trend increases in annual flow-weighted concentrations of NO3 ^-1 in stream water and increases in the seasonal amplitude and duration of NO3^-1 concentrations during 1972-1994. These stream water chemistry trends were partially attributed to significant increases in NO3^-1 and NH4⁺¹ concentrations in bulk precipitation over the same period and/or reduced biological demand due to forest maturation. Evidence for stage 3 of N saturation, where the watershed is a net source of N rather than a N sink, was found for the most disturbed watershed at Coweeta.

Long-term research on upland white spruce reproduction at Bonanza Creek LTER

Date Presented: Friday Night

Lead Author: Glenn Juday
Primary Site: BNZ

Abstract: Monitoring of post-fire white spruce regeneration at Bonanza Creek LTER is the most detailed long-term study of natural regeneration process in the Alaska boreal forest. All seedling white spruce in the Reserve West hectare (100m X 100m) have been mapped and seedling survival and height elongation have been measured annually since 1988. In fall 2002 a total of 2,191 seedlings were alive out of 2,485 seedlings in the data base, made up of all seedlings ever discovered including those which died at some point. All seedlings belong to the 1983, 1987, and 1990 seed crops, reflecting the highly episodic nature of white spruce reproduction. Mean height elongation responds to the same factors that control radial growth; cool moist summer promote growth and warm dry summers limit growth. Mean height growth of all seedlings in 2002 (12.6 cm) and 2001 (12.1 cm) was the highest since establishment. Mean total height of all seedlings was 88.7 cm in fall 2002 compared to 78.8 cm in fall 2001. Previous results indicated that seedlings on this site escape severe competition from herbaceous vegetation, especially from Calamagrostis grass, in the height range of 100 to 150 cm. Seedlings that are taller than the critical height range and that have no overtopping shrub or tree canopy cover are in the free-to-grow stage and will likely become the new forest canopy of dominant trees. In fall of 2002, 684 seedlings were taller than 100 cm (27.5%), 378 were taller than 150 cm (15.2%), and 226 were taller than 200 cm (9.1%). Before the Rosie Creek Fire of 1983 that originated the monitored stand, the Reserve West hectare was a strongly white spruce-dominated stand, with 529 trees greater than 2 cm in diameter, of which 439 were white spruce. Competition from hardwood stems currently totaling 10 times the number of spruce stems will retard or preclude future spruce dominance, and continuing monitoring is providing the basis for predicting the outcome of white spruce-hardwood competition.

Lotic Intersite Nitrogen eXperiment (LINX) II: An experimental 15N study of nitrate uptake and retention in streams from reaches to landscapes

Date Presented: Friday Night

Lead Author: Patrick Mulholland
Co-Authors: Bruce Peterson2, Steve Hamilton3, Jennifer Tank4, Robert Hall5, Jack Webster6, Maury Valett6, Judy Meyer7, Walter Dodds8, Cliff Dahm9, Nancy Grimm10,Sherri Johnson11, Stan Gregory11, Linda Ashkenas11, William McDowell12, Stuart Findlay13, Geoff Poole14
Institutional Affiliations: 1Oak Ridge National Lab, 2Marine Biological Lab., 3Kellogg Biological Station, 4University of Notre Dame, 5University of Wyoming, 6Virginia Tech, 7University of Georgia, 8Kansas State University, 9University of New Mexico, 10Arizona State University, 11Or
Primary Site: CWT

Abstract: We have recently begun an intensive, inter-site study of the fate of nitrate in streams. Our research is designed to evaluate whether streams are important sites of N retention in the landscape and, more importantly, how human disturbances affect that retention. We are using field 15N-tracer experiments to determine the rates and factors controlling nitrate uptake and retention in relatively pristine streams and in streams that have been altered by agriculture or urban development. These experiments will allow us to test a variety of hypotheses dealing with the impacts of human disturbances on streams, including effects on channel morphology, hydraulics, biological activity, and N retention. At each of eight sites distributed across diverse biomes throughout the U.S., we are performing tracer-level 15N-nitrate addition experiments in 9 streams: 3 reference, 3 agricultural and 3 urban (for a total of 72 streams). Each experiment consists of a 24-h addition of 15N-nitrate and longitudinally distributed measurements of 15N in water and in various benthic organic matter pools to determine in-situ rates of nitrification, assimilatory uptake of nitrate, and denitrification in each stream. We will use our experimental results to develop a general, process-based model of nitrate retention in stream reaches. We then will extend our results to much larger spatial scales by combining our stream model with GIS-based information on hydrography and land use to predict nitrate retention in a 5th or 6th order river basin at each of the eight study sites. We will test these predictions with synoptic field measurements of stream nitrate concentrations within each basin. The validated river basin model will be an important land-use planning and management tool for controlling the N loading of lakes and coastal ecosystems.

LTER Data Sets for TIEE (Teaching Issues & Experiments in Ecology)

Date Presented: Saturday Night

Lead Author: Charlene DAvanzo
Co-Authors: Bruce Grant, Jason Taylor, Dan Udovic
Institutional Affiliations: Hampshire College, Widener University, Ecological Society of America, University of Oregon
Primary Site: NONE

Abstract: Teaching Issues and Experiments in Ecology (TIEE) is designed to help college ecology faculty include more student active teaching in lecture and lab. It is an NSF-funded, ESA-sponsored collection of teaching materials on the ESA website. Authors write TIEE EXPERIMENTS (inquiry-based labs) and ISSUES (based on figures from published papers for lecture) which are peer reviewed and published on the site. Successful submissions must be both scientifically sound and pedagogically innovative. LTER data can be the centerpiece of a new section of TIEE called DATA SETS. We have DATA SETS from Hubbard Brook and North Temperate Lakes in which college students work with data on excel files to learn about long term stream flow and ice-off data. We seek DATA SET submissions for other LTER sites and will work closely with authors. Although TIEE is new, it is already widely used by college faculty and therefore the impact of LTER data on the TIEE site will be large.

LTER Dissolved Organic Nitrogen Intersite Comparsion (DONIC)

Date Presented: Saturday Night

Lead Author: Mark Williams
Co-Authors: Diane McKnight, William McDowell, John Melack, and Josh Schimel
Institutional Affiliations: University of Colorado - Boulder
Primary Site: NWT

Abstract: Our multidisciplinary research team has begun to address the role of organic nitrogen (N) in the N cycle by conducting intersite comparisons at the watershed scale. Here we present initial results from several LTER sites, including Hubbard Brook, Plum Island, Luquillo, Santa Barbara, Niwot Ridge, Baltimore, HJ Andrews, McMurdo Dry Valley, Toolik Lake, and Bonanza Creek, as well as the alpine Emerald Lake watershed. The purpose of this research is to quantify the importance of DON inputs and outputs at the watershed scale in an effort to: 1) test current and novel hypotheses in ecology; 2) compare DON dynamics in a diverse array of watersheds in order to suggest determinants of observed patterns; 3) explore the relationships between physical and biological characteristics of streams and their watersheds (topography, soil standing stocks of C and N); and 4) reveal deficiencies in the available data on DON dynamics at the watershed scale. Within these overall objectives, we have several additional goals, including (i) test new research tools for DON, including combustion, fractionation and fluorescence techniques; (ii) provide guidance to the LTER network on methods for DON sample collection and analysis; (iii) stimulate interest on research at the watershed scale within the LTER network; (iv) act as a steering committee to highlight the importance of DON to the ecological community; and (v) act as a repository for DON information that is available to the scientific community at large.

Managing Information for Long Term Ecological Studies on the HJ Andrews Experimental Forest

Date Presented: Friday Night

Lead Author: Theresa Valentine
Co-Authors: Don Henshaw
Institutional Affiliations: USDA Forest Service PNW Research Station
Primary Site: AND

Abstract: The HJ Andrews Experimental Forest is a living laboratory that provides unparalleled opportunities for the study of forest and stream ecosystems. During the last 21 years as a part of the National Science Foundation Long Term Ecological Research (NSF-LTER) program, the Andrews Experimental Forest has become a leader in the analysis of forest and stream ecosystem dynamics. Intensive forest ecosystem research, conducted on the Andrews Forest since the 1950's, has resulted in many diverse, long-term ecological databases and a strong commitment to information management. Ecological databases are managed through the Forest Science Data Bank (FSDB), which houses data sets from over 220 ecological studies. The FSDB is managed through an information management system that supports the collection, quality control, archival and long-term accessibility of data and associated metadata. Common metadata structures are currently being used to integrate spatial datasets with the ecological studies and allow data discovery and access through a single web interface.

Mapping and modeling two centuries of land use change in the southern Appalachian Mountains

Date Presented: Friday Night

Lead Author: Ryan Kirk
Co-Authors: Paul Bolstad
Institutional Affiliations: University of Minnesota
Primary Site: CWT

Abstract: Land use in the southern Appalachian Mountains has a rich and well-documented history since the time of European settlement. This poster summarizes on-going research efforts to map historic land use patterns in the Upper Little Tennessee River watershed surrounding the Coweeta Hydrologic Lab (approximately 150,000 hectares in western North Carolina and northern Georgia). An extensive combination of historic maps and surveys, forest and agriculture records, census data, aerial photographs and satellite images have been used to reconstruct land use since the early 1820s, with decadal coverage from the 1880s to the present. For time periods when no historic maps, photographic or satellite imagery are available, a probabilistic model is applied to predict spatial land use coverage, incorporating digital terrain models, historic records and existing spatial data from other time periods as predictors. From 1900 to present, forest cover in the area increased from 78 to 92%, coinciding with an 89% decrease in agricultural lands over the same period. These data are being used to assess the effects of land use change on water quality and regional carbon pools, as well as supporting a variety of other LTER research projects.

Measuring Nutrient Concentrations in Groundwater Discharge to the Southern Everglades

Date Presented: Friday Night

Lead Author: Tiffany McKelvey
Co-Authors: Rene M. Price
Institutional Affiliations: Florida International University
Primary Site: FCE

Abstract: The central organizing principal of the FCE LTER is that hydrologically mediated delivery of nutrients to the coastal zone from surface water runoff and tidal exchange with the Gulf of Mexico is responsible for increased primary productivity and a formation of an oligohaline zone along the coast. This research proposes an additional hypothesis, that discharge of brackish, nutrient laden groundwater to the overlying surface water contributes to the production of the oligohaline zone. To test this hypothesis, groundwater wells were sampled across the seawater-freshwater mixing zone in the Southern Everglades for total phosphorus and nitrogen concentrations. Preliminary data indicate that phosphorus concentrations are less than 1 uM in the groundwaters. Total phosphorus concentrations decreased downgradient in the freshwater portion of the aquifer and then increase within the oligohaline zone. A similar relationship is observed in the overlying surface waters. Further sampling and analysis will provide additional data on total nitrogen in the same area. The groundwater concentrations obtained from this project will be combined with concentrations of these nutrients currently measured in surface water (as part of the FCE LTER) and rainwater through a mass balance model to estimate the groundwater contribution of nutrients to the Everglades surface water.

Mechanistic linkages between global change, plant species traits, and nitrogen mineralization.

Date Presented: Friday Night

Lead Author: Jason West
Co-Authors: David Wedin, Sarah E. Hobbie, Peter B. Reich
Institutional Affiliations: University of Minnesota, University of Nebraska - Lincoln
Primary Site: CDR

Abstract: Declining biodiversity, elevated atmospheric CO₂, and N deposition are important global changes that strongly affect terrestrial ecosystems. As N limitation is a common feature of terrestrial ecosystems, the response of N cycling to these global change factors may shape overall ecosystem response to global change. We examined the consequences of species identity, CO₂ and N addition for gross and net N mineralization rates in a long-term experiment (BioCON) in N-limited grassland plots in central Minnesota. Consistent with previous research, tissue N concentrations were positively correlated with net N mineralization rates across all treatments for monocultures of sixteen different species. In contrast, gross N mineralization rates were negatively correlated with tissue N concentrations. This negative correlation was likely caused by greater productivity of more nitrogen-use-efficient species that supplied more carbon to the soil, and therefore fostered greater rates of gross N mineralization. Since net N mineralization is the difference between gross N mineralization and immobilization, the positive effects of tissue N concentrations on net N mineralization therefore arose from their effects on N immobilization. As the species observed in this experiment showed increases, decreases and no change in tissue N concentration in response to changes in CO₂ and N, species-specific changes in tissue chemistry and their consequences for N immobilization may explain the significant interactions between species, atmospheric CO₂ and N addition on net N mineralization. No such interactions were observed for gross N mineralization. Our results suggest that species-specific responses to atmospheric CO₂ and N deposition may significantly affect the direction and magnitude of N cycling responses to these global changes.

Methanol-Induced Shifts in Acidobacterial Diversity and Isolation of a Novel Acidobacterium from Soil

Date Presented: Saturday Night

Lead Author: Stephanie A. Eichorst
Co-Authors: B.S. Stevenson, C.D. Engles, J.A. Breznak, T.M. Schmidt
Institutional Affiliations: Michigan State University
Primary Site: KBS

Abstract: Soil is a heterogeneous environment containing over 4,000 species of bacteria per gram. However, the physiological diversity of the soil microbiota is poorly understood, since most of its phylogenetic diversity is not well represented in culture, such as the Acidobacteria division. We sought to extend observations done by others suggesting that some acidobacteria are methylotrophs, based on the accumulation of 13C in acidobacterial DNA upon incubation of soils with 13C -methanol. Microcosms were established with soil from the Kellogg Biological Station Long Term Ecological Research (KBS LTER) site in Hickory Corners, Michigan and incubated with methanol. A steady decrease in methanol was observed over 40 days of incubation. Statistical analyses (LIBSHUFF), performed on PCR-amplified Acidobacterium 16S rDNA libraries made from soil samples before and after treatment, suggested that methanol enriched for a phylogenetically cohesive group of acidobacteria. The clade enriched with methanol also accommodated a novel Acidobacterium (strain KBS 89) we recently isolated from the same soil; using minimal media incubated under 95% air/ 5% CO2. Homologous media incubated in air alone did not yield any acidobacteria detectable by “Plate Wash PCR” (a facile screening technique developed in our laboratory), suggesting that elevated levels of CO2 facilitated the growth of the isolate. Acidobacterium str. KBS 89 is a nonmotile rod measuring 0.5 μm x 1μm; catalase and oxidase negative; and produces an extracellular matrix causing cells to stick together tightly in colonies and form clumps in liquid culture. The closest phylogenetic relative to strain KBS 89 is an Acidobacterium recently isolated from an Australian pasture. Based on 16S rRNA, we estimate that Acidobacterium in KBS LTER soil represent 1-7% of the total microbial population. Acidobacterium str. KBS 89 and the ecological role of acidobacteria in soil is the object of continued investigation in our laboratory.

Microbial interactions on decaying Spartina alterniflora in a GCE-LTER salt marsh

Date Presented: Friday Night

Lead Author: Justine Lyons(1), Erin Biers(1)
Co-Authors: SY Newell(2), MA Moran(1), JT Hollibaugh(1)
Institutional Affiliations: 1) Univ. of Georgia, Athens, GA, 2) Univ. of Georgia Marine Institute, Sapelo Island, GA.
Primary Site: GCE

Abstract: Bacteria control organic matter (OM) decay in marine ecosystems, while fungi dominate initial OM decay in most terrestrial systems. Coastal environments are interfaces between these two habitats; therefore, it is not surprising that fungi and bacteria both play important roles in the decomposition of a dominant salt marsh grass, Spartina alterniflora. Ecological and physiological interactions between the co-occurring decomposer groups may alter the fate of vascular plant-derived OM in estuarine ecosystems. We studied bacterial-fungal (B-F) interactions using integrated biogeochemical and molecular approaches to determine how those interactions are manifested and whether they affect the decomposition of vascular plant material in the salt marsh. We used two types of laboratory microcosm systems and conducted manipulative field studies of decaying plant material to investigate microbial interactions on decaying Spartina leaves from the Georgia Coastal Ecosystems LTER field site. Results of one microcosm experiment suggest that fungi alone degrade significantly more Spartina than in combination with bacteria or when bacteria were present alone. In addition, two to three times more detrital carbon was routed to DOC rather than to CO2 if fungi were present alone. Another other microcosm experiment suggested that a dominant fungus released small quantities of fine particulate OM, highly labile DOC, and high levels of nitrogen-rich soluble material from Spartina blades when separated from bacteria. Finally, field experiments show that manipulating the fungal community on decaying Spartina may affect the composition of the co-occurring bacterial community. These types of experiments will continue to improve our understanding of B-F interactions and the consequences of these interactions to the decomposition of vascular plant material in estuarine ecosystems.

Modeling Above Ground Biomass and Decomposition of Cladium jamaicense in the Florida Everglades

Date Presented: Friday Night

Lead Author: Gustavo A. Rubio
Co-Authors: Daniel L. Childers, Emilie Verdone
Institutional Affiliations: Florida International University
Primary Site: FCE

Abstract: Sawgrass (Cladium jamaicense Crantz) is the common and characteristic plant of the Everglades freshwater marsh ecosystem, covering 65-70% of the marsh in dense monospecific stands. Sawgrass above ground biomass was calculated in two sites from February 2002 to August 2003 by bimonthly measuring three non-destructive m2 plots. Our biomass model predicts that the three main physiological traits responsible for sawgrass biomass are culm diameter at the base, flower height, and sum of the length of the leaves squared. Our model suggests that during this time period the average plot contains 220 gdw/m2. Also within each plot, three sawgrass plants were chosen and there leaves were individually tagged as they emerged from the culm with small colored bands and counted bimonthly, allowing for each leaf to be tracked throughout its lifetime. From these data we calculated leaf mortality, and sloughing rates. The average leaf lived approximately 4.5 months, and remained on the plant for an additional 7 months until sloughing off. The decomposition process was estimated using a litter bag experiment. The experiment was set to manipulate the decomposition cycle of sawgrass leaves, meaning first when the leaves die and remain attached to the plant (dry treatment), and then when the leaves are sloughed off by the plant (wet treatment). Litter bags for the dry treatment were attached to the periphery of a mesocosm above the water surface, and litter bags that experienced the wet treatment were placed on the soil surface. Preliminary results show that sawgrass leaves that were subjected to the dry treatment decompose at .0600 %/day and leaves that experience the wet treatment decompose at .1200 %/day. Essentially for sawgrass, its decomposition cycle acts as a “two step heat sink” by removing biomass from the plant and reallocating this lost biomass into the DOM pool. Finally, we close our model by trying to relate DOM in the water to sawgrass above ground biomass.

Modeling mixing time scales and transport of dissolved substances in the Altamaha River estuary

Date Presented: Friday Night

Lead Author: Joan E. Sheldon
Co-Authors: Merryl Alber
Institutional Affiliations: Univ. of Georgia
Primary Site: GCE

Abstract: This project focuses on 1) estimating flushing (freshwater transit) times and residence times for the Altamaha River estuary, Georgia, by several different methods (fraction of freshwater models and box models) and 2) using 1-D optimum-boundary box models to simulate the movement of dissolved pollutants or other conservatively mixing constituents through the estuary. Freshwater transit time estimates from simple steady-state box models were very similar to flushing times but depended on river flow. As river discharge increases from 185 to 538 m3 s-1, flushing times decrease from 7.2 to 2.7 d. When box models were used to simulate both the movement of tracer within the estuary and its rate of removal, it moved toward an area 4-6 km upstream of the mouth, where it remained centered as overall removal continued. Movement toward this zone was observed regardless of flow rate or the point of tracer introduction, suggesting that this area could be a slowly flushing node in the Altamaha River estuary. Maximum exposure to tracer, measured as the amount of time that concentration exceeds a given threshold, depends on where in the estuary tracer is released. Simulations of the type presented here are useful for evaluating the conservative movements of both point- and non-point-source constituents in the estuary.

Modeling the Spatial Distribution of Snow in a Rugged Alpine Valley

Date Presented: Saturday Night

Lead Author: Tyler Erickson
Co-Authors: Mark W. Williams
Institutional Affiliations: Institute of Arctic and Alpine Research
Primary Site: NWT

Abstract: One of the most challenging problems in snow hydrology is understanding the spatial distribution of snow properties in montane catchments. Natural snow variability is extreme due to complex controls. Many authors have found relationships between topographic parameters and snow distribution, but conclusions are based on datasets that span one or two years and it is not known whether the results are specific to the particular years of the study. Research was conducted in the Green Lakes Valley, an east-facing headwater catchment that abuts the Continental Divide and is part of the Niwot Ridge LTER. Snow depth surveys at maximum accumulation were conducted from 1997 to 2003. Snow distribution was modeled using a combined deterministic and stochastic approach. The deterministic trend component was modeled using three approaches: a constant mean, a linear combination of linear topographic parameters, and a linear combination of non-linear topographic parameters. The topographic parameters considered included elevation, slope, an index of total radiation, an index of wind exposure, and an index of snowdrift formation. Some topographic parameters were found to be significant predictors of snow depth for each of the years. Other topopgraphic parameters were found to be significant predictors for some years, while insignificant for other years. The stochastic component is used to characterize the spatial correlation between measurements. The range and variance of spatial correlation were found to be persistant between years. Furthermore the range and variance can be related to the total cumulative precipitation of the winter. This study was possible due to the availability of a multi-year dataset of snow surveys supported by the LTER network.

Molecular characterization of dissolved organic nitrogen (DON) in the Florida Coastal Everglades (FCE): Preliminary results

Date Presented: Saturday Night

Lead Author: Kathleen Parish (1)
Co-Authors: Nagamitsu Maie (1), Vera Jones (2), George Wolff (2), Heike Knicker (3), Ronald Benner (4), Rudolf Jaffé (1)
Institutional Affiliations: (1) Florida International University, (2) University of Liverpool, United Kingdom, (3) Technische Universität München, Germany, (4) University of South Carolina
Primary Site: FCE

Abstract: The Florida Coastal Everglades (FCE) is a unique oligotrophic environment where most of the nitrogen is in an organic form. While the Everglades Restoration Project will increase water flow and change water quality to these wetlands, there is some concern that the water entering the marine ecosystem to the South will result in increased nutrient loadings causing algal blooms and other related environmental problems. While such nutrients are expected to be mainly in the form of DON, there are few studies on the detailed chemical characteristics and bioavailability of such materials. Thus, our objectives in this study are to determine the chemical characteristics of DON, and to better understand its dynamics in the FCE. Seasonal variation in the abundance of labile proteinaceous materials in both Shark River Slough and Taylor Slough were determined monthly by fluorescence spectroscopy (synchronous fluorescence), fractionation of DOM into humic- and non-humic fractions using insoluble polyvinylpyrrolidone (PVP) and by molecular weight determinations using SEC. Detailed molecular characterization of DON was conducted biannually (wet/dry season) for the high molecular weight (HMW) DOM, concentrated using tangential flow ultrafiltration (<0.2µm, > 1kDa). These characterizations included amino acid composition analysis after hydrolysis, protein fingerprinting using electrophoresis, nitrogen stable isotope ratio analysis, and 15N CPMAS NMR spectroscopy. The preliminary results suggest that most of the DON in the FCE is protein-like materials, and that DON has been subjected to only early stages of diagenesis. Higher abundances of protein-like materials were observed in Florida Bay compared to the freshwater Everglades suggesting a mainly autochthonous source in this estuary.

Molecular characterization of high molecular weight dissolved organic matter (HMWDOM) in the Florida Coastal Everglades (FCE)

Date Presented: Friday Night

Lead Author: Nagamitsu Maie (1)
Co-Authors: Chengyong Yang (1), Toshikazu Miyoshia (2), Kathy Parish (1), Rudolf Jaffé (1)
Institutional Affiliations: (1) Florida International University, (2) National Institute of Advanced Industrial Science and Technology, Japan
Primary Site: FCE

Abstract: The FCE is a unique, extremely oligotrophic, subtropical ecosystem and one of the largest wetlands in the northern hemisphere. Nutrients have been found to be mainly in the organic form, and as such, this DOM is believed to fuel the microbial loop in this system. It is therefore essential to investigate the DOM dynamics to better understand the biogeochemical processes in the Everglades. To investigate the influence of vegetation and topography on the DOM composition throughout the FCE, water samples were collected along the two major drainage areas, namely Shark River Slough (SRS) and Taylor Slough (TS). The high molecular weight DOM (HMWDOM; < 0.7 µm, > 1 k Da) was isolated using a tangential flow ultrafiltration system, and the carbon, lignin phenol, and neutral sugar composition analyzed by 13C CPMAS NMR spectroscopy, off-line TMAH thermochemolysis, and TFA hydrolysis, respectively. The HMWDOM in the FCE was found to contain high relative abundances of potentially labile, non-humic substances such as polysaccharides compared to other aquatic systems. The observed molecular characteristics suggest that HMWDOM leached from senescent plant materials and exudates from biomass rather than soil-derived DOM are important sources in this system. This is particularly the case in Florida Bay, where autochthonous sources seem to dominate DOM inputs. Florida Bay DOM shows significantly lower lignin-phenols concentrations as well as aromatic C content, and a more elevated carbohydrate and protein content compared to the freshwater Everglades. Freshwater Everglades derived DOM seems to undergo rapid photodegradation and possibly flocculation when entering the Florida Bay estuary.

MONITORING AND UNDERSTANDING LONG-TERM LARGE-SCALE ENVIRONMENTAL CHANGE ACROSS SOUTHERN AFRICA

Date Presented: Friday Night

Lead Author: Johan Pauw¹
Co-Authors: Joh Henschel²
Institutional Affiliations: ¹South African Environmental Observation Network, National Research Foundation, Private Bag X 2600, Pretoria 0001. ²Gogabeb Training and Research Centre, P.O. Box 953, Walvis Bay, Namibia
Primary Site: INT

Abstract: The Environmental Long-Term Observatories Network of Southern Africa (ELTOSA) is a regional LTER network of country Environmental Observatories Networks (EON) encompassing the natural environments and their socio-economic context. In the global context, Southern Africa represents a unique geographic location. There is a great diversity of habitats and people, including extremes represented in several deserts and rainforests, escarpments and mountains, woodland savannahs and inselbergs, perennial and ephemeral rivers, swamps, lagoons and lakes, warm coral reefs and cold upwelling currents, and oceanic islands ranging from tropical to uninhabited subantarctic. The region includes four global biodiversity hotspots and contains many large and famous national parks, game reserves, or other kinds of wilderness areas, harbouring not only fauna and flora, but also entire ecosystems and human settlements. There is a need to monitor the same kinds of habitats and parameters at different sites in order to fully understand the spatial dimensions of ecosystems drivers and response mechanisms, or to replicate observations. While EON monitors spatial shifts in species, vegetation types and productivity, it will be important to relate these to the dominant issues of climate change, water sources, use and needs, as well as land tenure, land transformation and land use. Rural people in Southern Africa depend on natural resources - many are poor and in dire need of improved livelihood security. They are subject to the vagaries of an already harsh environment and the shortage of resources and education that they have to cope with render then even more vulnerable to extreme events caused by climate change. The main challenges facing EON in Southern Africa are of the institutional kind. There is a need to maintain local leadership with regards to foreign funded long-term environmental research programmes.

Morphostatic Long-Term Hypsometric Analysis of Coastal Bay Environments, Hog Island Bay, Virginia

Date Presented: Saturday Night

Lead Author: Kathleen Overman
Primary Site: VCR

Abstract: Sea level has been rising at a variable rate since the end of the last glaciation approximately 18,000 years ago. As the transgressing sea inundates the shore areas a series of landform state changes occur in coastal regions. One such change of state in a coastal paleo-river channel is from an estuary into a coastal lagoon. At large temporal intervals (thousands of years) the hypsometry of a coastal lagoon varies as a result of sea level rise due to these changes of state. Using a morphostatic technique, the time period in which an estuary transforms into a coastal lagoon can be determined from a series of hypsometric curves created for a basin over large temporal intervals. This time period can be verified using an analysis of the associated hypsometric integral for each curve, as well as using an analysis of the potential marsh surface area available for colonization and the intertidal surface area. Using this type of analysis, Hog Island Bay, Virginia is determined to have transformed into a coastal lagoon between 4000 and 3000 years before present (ybp). The results of this project advance the spatial analysis and morphostatic analysis methodologies for coastal research, and shed light on the transformation structures of coastal basins undergoing sea-level rise.

Mycorrhizal Symbiosis and Fire in South African Savannas and North American Prairies

Date Presented: Saturday Night

Lead Author: David Hartnett¹
Co-Authors: Andre Potgieter², Gail Wilson¹
Institutional Affiliations: ¹Kansas State University, ²South African National Parks
Primary Site: KNZ

Abstract: Mycorrhizal symbiosis is a key factor influencing grassland structure and function. Studies at the Konza Prairie LTER have shown that arbuscular mycorrhizal fungi (AMF) strongly regulate plant growth, competition, population and community dynamics, and responses to fire and grazing in tallgrass prairie. This study assessed mycorrhizal symbiosis under various fire regimes in southern African savannas, ecosystems similarly dominated by perennial C4 grasses and subjected to fire and grazing. Mycorrhizal root colonization (MRC) and root system architecture (RSA) were studied in 18 grass species across contrasting experimental fire frequency treatments in the Kruger National Park, South Africa. All species were colonized by AMF, although MRC was variable among species and sites, and generally higher in more nutrient poor sandy soils than on clay soils. Among sites, MRC decreased with increasing annual precipitation, a pattern consistent with North American grasslands. Both mycorrhizal symbiosis and RSA were strongly affected by fire, with an increase in MRC and a decrease in root branching and fine root development with decreasing fire frequency. Greater water limitation in frequently burned sites may result in greater fine root development and branching, which in turn results in reduced plant dependency on AMF for acquisition of soil resources. Reduced MRC in frequently burned savanna may also be driven by higher phosphorus availability or P:N ratios, or indirect effects due to higher grazing intensities in frequently burned sites. Overall, MRC levels in these African savanna grasses were 2 to 3 times greater than grasses in sites of similar soil fertility and precipitation in North American grasslands. This may reflect significant differences in the co-evolutionary history of AMF and their host plants, or in levels of herbivory between these two systems.

Mycorrhizal symbiosis and insect herbivory in tallgrass prairie

Date Presented: Saturday Night

Lead Author: Abigail R. Kula
Co-Authors: David C. Hartnett, Gail W.T. Wilson
Institutional Affiliations: Kansas State University
Primary Site: KNZ

Abstract: Mycorrhizal symbiosis regulates plant composition and diversity and may influence plant-herbivore interactions in grassland communities. We conducted greenhouse and field studies to determine the effect of mycorrhizal fungi on insect herbivory of tallgrass prairie plants. We manipulated mycorrhizal colonization of eight plant species in greenhouse microcosms to examine mycorrhizal effects on grasshopper feeding and also plant and fungal response to herbivory. We also grew single species in caged pots to study the role of mycorrhizal dependence in nymphal development of mixed- and grass-feeding grasshoppers. In field transects of long-term fungicide-treated and control plots, we surveyed patterns of insect feeding intensity on plants growing with and without mycorrhizal fungi. Our results indicate no strong effects of mycorrhizal symbiosis on grasshopper feeding or development. Feeding levels on mycorrhizal versus non-mycorrhizal plants in microcosms did not differ significantly. Very few factors of grasshopper development were affected by mycorrhizal responsiveness of the host plant, and more frequently, developmental differences were based on natural feeding specificity (i.e. grass versus forb). Insect feeding levels on mycorrhizal plants were higher than on fungicide-treated plants in field transects. Mycorrhizal symbiosis positively affected plant re-growth following herbivory. Depending upon the level of herbivory and plant dependence on the symbiosis, some grazed plants in mycorrhizal microcosms had higher biomass than their non-defoliated counterparts. AM fungal colonization of grazed plants was higher than that of ungrazed plants in microcosms. This is the first study to examine mycorrhizae-herbivore interactions of multiple co-occurring plant species displaying a range of mycotrophy.

N retention as a function of land use and watershed size in northeastern MA.

Date Presented: Saturday Night

Lead Author: Wil Wollheim
Co-Authors: Brian Pellerin, Charles Vorosmarty, Charles Hopkinson
Institutional Affiliations: UNH, UNH, UNH, MBL
Primary Site: PIE

Abstract: Increased anthropogenic N loading is leading to many harmful effects, including coastal eutrophication and anoxic dead zones. Land use and watershed size influence water and N delivery to the coastal zone. We looked at N exports for the 2001-2002 water year from headwater catchments of contrasting land use in the Plum Island Ecosystem watershed (PIE-LTER) in Massachusetts. We compared these exports to those for the composite Ipswich and Parker watersheds within which the headwater catchments are nested. We combined temporally intensive monitoring (2 headwater catchments of contrasting forested and residential land use, 2 composite larger catchments), spatially extensive monitoring (16 additional headwater sites) and GIS data sets (land use, population, impervious cover) to determine N fluxes, and construct water and N budgets for each catchment. Annual water runoff was 26% of precipitation inputs in the residential watershed (25% impervious), and 10% in the forested site (6.5% impervious). Annual runoff was 26% and 31% in the Parker and Ipswich, respectively. N retention ranged from 80% in the residential catchment to 96% in the forested headwater catchment. The larger composite watersheds were intermediate. A larger proportion of N export was as DON from the larger composite watersheds than in the headwater catchments. Variability in annual flow-weighted DIN concentrations in the headwater catchments could be explained by the % residential area (r2 = 0.58, n=16), or by total population (r2 = 0.49, n=16). Comparison with predictions from a simple loading model (Caraco et al. 2003) shows observed DIN exports are less than predicted. Model predictions are improved if river retention is increased to account for potentially higher aquatic N retention due to low flow conditions in 2001 – 2002. Preliminary analysis suggests that N retention declines with increased impervious surface area in the headwater catchments due to increased water runoff.

Near-continuous sampling of soil N2O emissions.

Date Presented: Saturday Night

Lead Author: Sven Bohm
Co-Authors: Phil Robertson
Institutional Affiliations: Kellog Biological Station
Primary Site: KBS

Abstract: We are using automated static chambers for frequent measurements of N2O emissions from soils under four different agricultural management systems (conventional, no-till, and organic soybean-wheat-corn rotations and continuous alfalfa). N2O emissions are sampled four times per day, and simultaneous measurements of soil moisture and temperature provide ancillary emission data as do periodic soil nitrate measurements. Fluxes vary smoothly over the time period thus far measured, suggesting that we are capturing most of the temporal variability present in the systems. N2O emissions are strongly diurnal and often vary more than three-fold over a single day. Longer term trends appear related to soil moisture, temperature, and nitrogen availability. In the spring fluxes were highest in the alfalfa, followed by the no-till and the organic systems. Data will be used to test current models of N2O emission including DAYCENT.

Neighborhood ecosystems: Human-vegetation-climate interactions in a desert metropolis

Date Presented: Friday Night

Lead Author: Nancy Jones (1)
Co-Authors: A. Brazel (1) ,C. Eisinger (1), S. Harlan (1), B. Hedquist (1), S. Grineski (1), G. D. Jenerette (1), L. Larsen (2), M. A. Lord (1), J. Parker (1), L. Prashad (1), N. Selover (1), and W. L. Stefanov (1)
Institutional Affiliations: (1) Arizona State University, (2) University of Michigan
Primary Site: CAP

Abstract: This project investigates the interactions of human activities and biophysical-climatological processes on a regional and a neighborhood scale in the Phoenix, Arizona, metropolitan area. Investigators analyzed biophysical and social information at the census tract scale to determine regional heterogeneity. Initial findings show that a SAVI index correlates with surface temperature. As expected, population density in the urban area is correlated positively with warmer census tract minimum temperatures, as well as with census tract SAVI minimum values. Increased census tract surface temperature averages also correlate with age of housing and lessening income levels. These associations could be confounded by other important factors (also under investigation), such as topographic relief. At the neighborhood scale, investigators performed a pilot comparison of climatic variables (air temperature, humidity, and levels of shade) with demographic data (income level, ethnicity, etc.) and neighborhood vegetative indices (NDVI and SAVI). Initial results from six neighborhoods did not suggest a strong correlation between physical and social variables possibly due to the narrow variability of biophysical neighborhood characteristics among the sites chosen. As part of a Biocomplexity NSF grant and an IGERT workshop, investigators added further neighborhoods over a larger range of the biophysical and social variables and are currently analyzing data at the neighborhood scale to determine how temporal and spatial variation among eight neighborhoods exhibits a range of differences within the region.

Nitrogen Saturation Experiments in the Bisley Watersheds and Rio Icacos: Soil Trace Gas Emissions and Solution Chemistry Responses

Date Presented: Saturday Night

Lead Author: Jordan Macy1
Co-Authors: William H. McDowell1, Frederick N. Scatena2
Institutional Affiliations: 1University of New Hampshire, Durham, New Hampshire USA; 2University of Pennsylvania, Philadelphia, Pennsylvania USA
Primary Site: LUQ

Abstract: Plots in two watersheds of the Luquillo Experimental Forest were fertilized in January and June 2002 as part of a long term experiment designed to test current paradigms of N saturation in tropical forests. Treatment plots in lower montane cloud forest and lowland tropical rainforest received fertilizer (NH4NO3) at rates of 25 kg N ha-1, for an annual rate of 50 kg N ha-1. N2O soil emissions were measured beginning December 2000 and sampled monthly prior to fertilization, and soil solution chemistry measurements began in October 2000. Three sets of measurements were taken roughly every two weeks over an eight week period following each fertilizer addition. Baseline fluxes of N2O-N from the Icacos plots were over twice those observed in Bisley (7.23 kg N ha-1 y-1 and 2.72 kg N ha-1 y-1). Trace gas fluxes increased with continued N application. In the Icacos, the second fertilizer application resulted in a doubling of the amount of applied N lost as gas, from 2.29 to 5.12 kg N ha-1 (9% of added N and 20% of added N, respectively). In Bisley, the first two applications also resulted in doubling of gaseous losses, from 1.32 to 2.38 kg-N ha-1 (5% of added N and 10% of added N). In soil solution, total dissolved nitrogen concentrations increased substantially in the Icacos, yet Bisley lysimeters showed only slight responses to fertilization suggesting greater immobilization in litter decomposition, biomass accumulation, and possibly soil adsorption. We are presently testing the latter two hypotheses.

Nitrogen Versus Phosphorus Limitation of Benthic Primary Production in Florida Bay

Date Presented: Friday Night

Lead Author: Thomas A. Frankovich
Co-Authors: James W. Fourqurean
Institutional Affiliations: Florida International University
Primary Site: FCE

Abstract: Restoration of the greater Everglades ecosystem will increase freshwater input to Florida Bay. Ecosystem health will be dependent upon the quality and quantity of that water. Recent evidence suggests that, depending on location, either nitrogen or phosphorus limitation exists for Florida Bay primary producers. Increased freshwater flow, as envisioned by the Restoration Plan, may increase loadings of both nitrogen and phosphorus into the Bay. The regional and temporal effects of these increased loadings on benthic primary production are a focus of this investigation. To determine nutrient limitation for benthic primary producers, and to assess the regional and temporal variability of N vs. P limitation, long-term replicated 2X2 factorial experiments designed to assess the effects of nutrient additions (N, P, N + P) are being conducted at six seagrass sites within Florida Bay. Sites were selected in northeastern, central and western Florida Bay along an existing nutrient availability gradient (Fourqurean et al., 1993; Boyer et al., 1997). Slow-release nitrogen fertilizer and phosphorus as granular phosphate rock are being applied to the sediment surface at rates of 0.62 g N m-2 day-1 and 0.09 g P m-2 day-1. The following response variables are being measured quarterly: Thalassia testudinum biomass and productivity, Braun-Blanquet abundance, and leaf CNP, total epiphyte load, epiphyte chlorophyll-a, epiphyte accumulation rate, and benthic chlorophyll-a. Preliminary results indicate that regional variability in benthic chl-a, epiphyte loading, Thalassia testudinum biomass, productivity, and CNP was greater than fertilization treatment effects at the early stages of the field experiments. At month four of fertilization, phosphorus treatments were exhibiting greater benthic chlorophyll concentrations. Further results from the third quarterly sampling of the long-term fertilization experiments will be presented.

North Temperate Lakes LTER

Date Presented: Saturday Night

Lead Author: Steve Carpenter
Co-Authors: NTL CoPIs
Institutional Affiliations: University of Wisconsin - Madison
Primary Site: NTL

Abstract: The goal of the North Temperate Lakes (NTL) LTER is to understand the long-term regional ecology of temperate inland waters. Our vision is to gain a predictive understanding of aquatic ecology at longer and broader scales than has been traditional in limnology – focusing on decadal time scales in landscapes of forested, agricultural, and urban catchments. The overarching question guiding this collaborative research is “How do biophysical setting, climate, and changing land use and cover interact to shape lake characteristics and dynamics over time (past, present, future)?”. Our interdisciplinary research group includes ecologists, hydrologists, climatologists, chemists, demographers, economists, rural sociologists, and specialists in remote sensing and information management. Four recent examples of ongoing work that highlight multiple aspects of this research are given. The Satellite Lakes Observatory Initiative has parameterized a model of lake clarity using remotely-sensed satellite imagery data to generate a better understanding of the spatial variability of water quality in the landscape and enhance our potential for predicting susceptibility to future impacts. The Buoy Project, through the use of instrumented sensors acquiring limnological measurements at sub-daily frequencies, has allowed us to investigate the short-term dynamics underlying year-to-year differences in lake ecosystems. Lake Circulation Models, capable of reconstructing general hydrodynamic patterns in three dimensions, have allowed us to quantify and predict environmental impacts such as algal bloom formation, water quality issues, and shoreline erosion. Lastly, the NTL Long-Term Monitoring Program has played a key role in alerting state management agencies to the recent invasion of the toxic blue-green alga Cylindrospermopsis raciborskii in the Madison Lakes, in addition to characterizing the spatial and temporal extent of the outbreak.

Northeastern Ecosystem Research Cooperative

Date Presented: Friday Night

Lead Author: Gary Lovett
Co-Authors: Tom Clair, Charles Driscoll, Christopher Eagar, Kathy Fallon Lambert, Myron Mitchell, Lindsey Rustad
Institutional Affiliations: Institute of Ecosystem Studies, Millbrook NY; Environment Canada, Sackville, NB; Syracuse University, Syracuse, NY; USDA Forest Service, Durham, NH ; Hubbard Brook Research Foundation, Hanover, NH; SUNY-CESF, Syracuse, NY; USDA Forest Service, Cumberland,
Primary Site: HBR

Abstract: The Northeastern Ecosystem Research Cooperative (NERC) is an initiative to promote collaboration among ecosystem research scientists in the northeastern U.S. and eastern Canada. The NERC facilitates regional-scale research, monitoring and assessment activities by: 1) initiating joint research projects, 2) sharing data and results, 3) participating in analysis and synthesis of regional environmental issues, and 4) increasing the level of communication among researchers, resource managers and policy makers interested in results of regional environmental research. The NERC consists of several task groups exploring particular issues. A steering committee facilitates interaction among task groups and organizes biennial meetings of the entire cooperative.

Nutrient dynamics of tropical rainforest streams

Date Presented: Saturday Night

Lead Author: Jody Potter
Co-Authors: Bill McDowell
Institutional Affiliations: University of New Hampshire
Primary Site: LUQ

Abstract: Dissolved nutrients can limit primary productivity in freshwater ecosystems, therefore an understanding of their retention and transport is critical. The study of nutrient dynamics is especially desirable in tropical environments where there has been less attention paid. Nutrient spiraling is the simultaneous cycling and transport of nutrients in lotic systems. Nutrient uptake is a measure of the efficiency of nutrient cycling and the limitation of those nutrients in stream environments. The main purpose of this study is to determine the nutrient dynamics of the headwaters of the Rio Icacos in the Luquillo Experimental Forest in Puerto Rico. Separate short term additions (about 6 hours) of NO3, NH4, PO4 and DOC will occur at base flow to determine the uptake rate of each nutrient in the stream as well as changes (if any) in concentrations of other nutrients resulting from the short term enrichments. Another purpose of this study is to examine nitrate dynamics of tropical headwater streams across changes in land use. Therefore, nitrate addition experiments will also occur in an agricultural (Quebrada Maizales) and urbanized (MTrib) stream. The final purpose of this study is to compare the nutrient dynamics of these streams to other streams in the Luquillo LTER site where nutrient additions occurred and unpublished data (McDowell) is available. Water samples will be collected prior and during the nutrient release and analyzed for NO3, NH4, PO4, DOC, TDN, and DON. Physical and chemical characteristics of the stream will be measured to provide insight into the uptake of the various solutes. The stream nutrient uptake length, velocity, and rate will be calculated according to the Stream Solute Workshop (1990). The data collected from this study will also be used in connection with the Lotic Intersite Nitrogen eXperiment (LINX) II, which will use these same streams in the first year of that study.

Nutrient Loading to Mediterranean Coastal Streams and Nutrient Export Coefficient Modeling

Date Presented: Saturday Night

Lead Author: Timothy H. Robinson
Co-Authors: A. Leydecker, J. M. Melack and A. A. Keller
Institutional Affiliations: Bren School of Environmental Science and Management, UC Santa Barbara
Primary Site: SBC

Abstract: Along the southern California coast, near Santa Barbara, we are measuring nutrient runoff from specific land uses and developing a model to predict nutrient export at a watershed scale. The area is characterized by a Mediterranean climate and short steep catchments producing flashy runoff. The six land use classes include chaparral, avocado orchards, greenhouse agriculture, open-field nurseries, residential, and commercial. Sampling sites are located on defined drainages or storm drains that collect runoff from relatively homogeneous areas representing each land use. Stream water samples are taken once a week during the rainy season, every two weeks during the dry season and every one to four hours during storms. We model flow at all sampling sites from measurements of stage derived from pressure transducers fixed to the bottom of the stream. Staff gauges are installed for monitoring stage during sampling. Outlet data from water year 2001 indicate loadings of nitrate to the near shore environment of 1, 2 and 10 kg ha-1 yr-1 from Carpinteria, Santa Monica and Franklin creeks respectively; 10 metric tons yr-1 of nitrate from Franklin Creek, a catchment dominated by intensive agriculture. A watershed scale model is being developed and calibrated to simulate nutrient export using the field data. The model is based on landuse, precipitation and antecedent soil moisture conditions. The objective is to create a robust model that uses derivable parameters in a simple and cost efficient manner, that can be extended to all coastal watersheds with similar land use and a Mediterranean climate. It is constructed in a dynamic environment of ArcGIS, Arc Hydro geodatabase model, Visual Basic for Applications (VBA) and MS Excel/Access. We are modeling and deriving export coefficients for NO3-N, NH4-N, and PO4-P (SRP).

Open Source Web Services Infrastructure for the LTER Network Climate Data Collections

Date Presented: Saturday Night

Lead Author: Tony Fountain
Co-Authors: Longjiang Ding, Peter Arzberger
Institutional Affiliations: San Diego Supercomputer Center (SDSC), the North Temperate Lakes Long-Term Ecological Research (NTL-LTER), H.J. Andrews Experimental Forest Long-Term Ecological Research (AND-LTER), Virginia Costal Reserve Long-Term Ecological Research (VCR-LTER)
Primary Site: NTW

Abstract: A standardized web services infrastructure integrated with the geographically distributed LTER Network resources is developed to address the dynamic cross-site data integration and analysis issues raised by the heterogeneous data formats used by the 24 LTER Network sites. The key is to provide a standard and easily automated data access mechanism for client processes. The architecture is composed of two parts: 1) the remotely-deployed data source wrapper web services; 2) a central web service which communicates with the distributed web services to handle cross-site data requests and analysis. The wrapper web services rely upon Ecological Metadata Language (EML) at the sites for data configuration information and provide access to data stored in Oracle, MySQL, and MS SQL Server databases. These services currently provide access to data from three key LTER Network sites: North Temperate Lakes (NTL), Virginia Costal Reserve (VCR), and H.J. Andrews Experimental Forest (AND). The services are standard SOAP-based Apache Axis message type services. They are written in such a way that the code can be reused at multiple sites without modification, saving the site managers from having to develop their own data-access web services. These services rely upon an open source software stack that includes Apache Tomcat and Axis. Future work includes expanding the services infrastructure to include other data sources (such as hydrology and spatial data and several PRAGMA research sites) and integrating the system with grid services standards.

Organic Matter Sources to Soils/Sediments of the Florida Coastal Everglades:

Date Presented: Friday Night

Lead Author: Ralph Mead
Co-Authors: Min Gao, Rudolf Jaffé*
Institutional Affiliations: Florida International university
Primary Site: FCE

Abstract: Everglades National Park (ENP) is about to undergo the world’s largest wetland restoration to bring freshwater flow to historical values. The increased freshwater flow is hypothesized to bring about changes in the organic matter dynamics of ENP thus altering preservation of organic matter in the sediments/soils, food webs and the type of organic material transported to the coastline. Therefore understanding OM dynamics at present will be important to discerning any changes brought about in the future by the increased freshwater flow. In this study, OM in vegetation, soils, sediments and suspended particulates was sampled and characterized by means of both bulk and molecular analysis. Samples were taken from the two major drainage systems of ENP, Shark and Taylor River Sloughs, including one tree island. Based upon molecular marker data, organic matter from emergent vegetation, higher plant material and periphyton contributes to the freshwater marsh sites of Shark and Taylor Rivers while mangrove and marine derived organic matter (seagrass) contribute to the estuarine sites. However, Shark River Estuarine organic matter dynamics were found to be quite different from those at the Taylor River Estuarine. Differences in tidal activity between the two systems allows for significant, seasonal submerged aquatic vegetation growth in Taylor while such vegetation is absent from Shark River Estuary. Therefore, the hydrology and the OM quality between Shark and Taylor River Estuarine sites are different, thus affecting OM transport and degradation processes. Mixing of OM transported from the freshwater marshes, derived from within the estuarine region and introduced by tidal activity from the Florida Shelf was assessed through a simple, molecular marker based model.

Palmer LTER Outreach: Education-by-Design

Date Presented: Saturday Night

Lead Author: Karen S. Baker
Co-Authors: Beth Simmons, Dawn Rawls
Institutional Affiliations: Scripps Institution of Oceanography, University of California San Diego
Primary Site: PAL

Abstract: The Palmer Long-Term Ecological Research (LTER) program, focused on Antarctic marine research since 1990, supports a Schoolyard LTER component engaged in interfacing with education and outreach communities since 1998. An Understanding-by-Design approach includes templates based on performance assessments in order to facilitate deeper understanding of science learning. Our evolving framework, responsive to national and state standards that enable students to learn about the world of science through inquiry and case based approaches, is anchored by the notion of design as a key element of the development process. Some examples of ongoing program activities include gathering outreach trunk materials, coordinating online field journaling efforts, and incorporating research materials and data into local modules. We work within a community of partners that links field participants and research scientists to the student in the classroom in coordination with technology, education, teacher, and communication centers.

Palmer LTER: Feeding modes of larval and juvenile Antarctic krill, Euphausia superba, and implications for winter survival

Date Presented: Saturday Night

Lead Author: Stephanie Oakes
Co-Authors: Robin Ross and Langdon Quetin
Institutional Affiliations: University of California-Santa Barbara
Primary Site: PAL

Abstract: Larval and juvenile Antarctic krill, Euphausia superba, are considered obligate grazers on sea-ice biota during the austral winter, when food sources in the water column are scarce. Krill are observed to exhibit two distinct feeding behaviors, compression filtration in the water column and scraping on the surface of winter sea-ice. An energetic comparison of these two feeding modes has not been conducted. To explore this, feeding experiments were conducted at Palmer Station, Antarctica, during February to March 2001 and November to December 2002. Laboratory-maintained larval and juvenile krill where fed naturally collected plankton or the diatom Nitzschia curta at winter temperatures (-1.5 to –1.8C), both in the water column and on artificially cultured surfaces. Results suggest that krill feeding on surfaces experience a delayed increase in ingestion rate with increasing food concentration. Thus, although maximal ingestion rates are similar for both feeding modes, krill may feed less effectively on surfaces at low food concentrations than in the water column. Low concentrations are similar to those found in the water column during winter and in sea-ice during early winter or when ice forms late. Energetic implications for daily carbon ration, growth and winter survival are considered.

Palmer LTER: Information Flow and Management

Date Presented: Saturday Night

Lead Author: Karen S. Baker
Co-Authors: Anna K. Gold, Frank Sudholt, Helena Karasti, Geoffrey C. Bowker
Institutional Affiliations: Scripps Institution of Oceanography-UCSD, University of California San Diego Lib
Primary Site: PAL

Abstract: Organizational repositories are being constructed today to address the needs of scientific information management in a digital environment. Given the social aspects of information, building useful information systems requires infrastructures that reflect the unified and expressive relationships of data, documents, people, institutions and partnerships. The Palmer Long-Term Ecological Research (LTER) program information management is working in partnership to explore articulation of the LTER community information management practices and to prototype a co-construction of a low barrier bibliographic referatory/repository. Just as information flows across electronic boundaries today, this work provides an opportunity to gain experience in crossing the traditional research domains (ecological and marine science, information science and digital library efforts, social science and participatory design approaches). The persistence of infrastructures for long-term scientific projects depends in part on offering low barriers for participation as well as on supporting heterogeneous inputs and outputs. Project goals include investigation of how short-term/local approaches can be compatible with long-term federation strategies since they are critical to initiating information flow, contributing to knowledge diversity, creating reflexivity in development processes as well as ensuring participant engagement and education. In considering the ramifications of sociotechnical issues and ontological codification on information collections, the importance of the multiple dimensions of design, the varied forms of formal and informal communication, and the nature of tacit and explicit knowledge are highlighted.

Palmer LTER: Patterns of distribution of major zooplankton species west of the Antarctic Peninsula over a 10-year period

Date Presented: Saturday Night

Lead Author: Robin Ross
Co-Authors: Langdon Quetin, Doug Martinson, Rich Iannuzzi, Sharon Stammerjohn and Ray Smith
Institutional Affiliations: University of California-Santa Barbara, Lamont Doherty Earth Observatory
Primary Site: PAL

Abstract: Data on the distribution of the dominant zooplankton species west of the Antarctic Peninsula have been collected each summer from January 1993 to now on the Palmer LTER 400 by 200 km sampling grid. Spatial-temporal analysis of these data is based on Empirical Orthogonal Functions (EOF). We show climatologies (long term averages) and standard deviates of the distributions of the most numerous zooplankters: Antarctic krill (Euphausia superba), two other euphausiids, a pteropod, and a salp. Patterns of distribution and examples of between-species interactions and species-to-environment interactions will illustrate the usefulness of the approach.

PALMER, ANTARCTICA LONG-TERM ECOLOGICAL RESEARCH PROJECT "Long-Term Ecological Research on the Antarctic marine ecosystem: Climate migration, ecosystem response and teleconnections in an ice-dominated environment"

Date Presented: Saturday Night

Lead Author: Hugh Ducklow¹
Co-Authors: K. S. Baker², A. C. Clarke³, W. R. Fraser⁴, D. G. Martinson⁵, L. B. Quetin⁶, R. M. Ross⁶, R. C. Smith⁶, M. Vernet²
Institutional Affiliations: 1-The College of William & Mary; 2-Scripps Inst. Of Oceanography; 3-British Antarctic Survey; 4-Polar Oceans Research Group; 5-Lamont-Doherty Earth Observatory; 6-Univ. of California-Santa Barbara.
Primary Site: PAL

Abstract: The central tenet of PAL is that the annual advance and retreat of sea ice is a major physical determinant of spatial and temporal changes in the structure and function of the Antarctic marine ecosystem. We now recognize the west Antarctic Peninsula (WAP) as a premier example of a climate-sensitive region experiencing major changes in species abundance and composition due to changes in range and distribution that are occurring in response to regional climate change manifested here primarily as a southern migration of principal climate characteristics (climate migration). In effect, the maritime system of the northern WAP is replacing the continental, polar system of the southern WAP along the peninsular climate gradient. This change is driven by regional warming, which is modulated by regional hydrography, sea ice processes and global teleconnections to lower latitude atmospheric variability. Changes in response to climate shifts are apparent at all trophic levels. We seek to understand the full ecological implications of climate migration in the WAP, and uncover the mechanisms linking them through teleconnections to global climate variability.

Parameter scaling of key hydrological, soil-erosion and nutrient parameters in an arid desert ecosystem

Date Presented: Friday Night

Lead Author: E. N. Mueller¹
Co-Authors: J. Wainwright¹, A. J. Parsons²
Institutional Affiliations: King’s College London, UK¹, University of Leicester, UK²
Primary Site: JRN

Abstract: The spatial distribution and small-scale variability of parameters relating to vegetation, soil and topography have a major influence on the numerical modelling of water, sediment and nutrient fluxes within heterogeneous arid and semi-arid landscape units. This small-scale variability has to be taken into account in the process of up-scaling environmental models from the plot to the catchment scale. An extensive field study was undertaken at the Jornada LTER site in southern New Mexico to understand better and quantify this small-scale variability of key hydrological, sediment and nutrient model parameters. Different parameters for spatially distributed hydrological and soil-erosion models vary and scale in fundamentally different ways. Therefore, common key model parameters have been collected and examined for their parameter-scaling properties. Parameters under investigation include vegetation and pavement cover, ponded infiltration rates and hydraulic conductivity, microtopography, the Darcy-Weisbach friction coefficient, soil moisture, particle size distribution, soil aggregate stability and nutrient content. A nested sampling strategy is used to obtain measurements at a range of different spatial scales from several metres (plant-interspace scale) to the medium-range variations of several tens of metres (shrub patch size). Geostatistical analysis is applied as a scaling tool to estimate the deterministic length scales of these parameters. The poster summarises the models that have been fitted to the various experimental variograms. These models have then been used for stochastic conditional simulations of intrinsic pattern formation at different scales. These results will permit the explicit representation of the short-range variations (such as plant-interspaces) and medium-range variations (such as patches) of model parameters in the grid structure of spatially distributed models and will give a framework to up-scale point measurements appropriately.

Parameterizing threshold values when leaf area indices are estimated from hemispheric digital images

Date Presented: Friday Night

Lead Author: Dowon Lee
Co-Authors: Kyounghee Kim, Taehee Hwang, Jiyeon Kim
Institutional Affiliations: Environmental Planning Institute, Graduate School of Environmental Studies, Seoul National University
Primary Site: INT

Abstract: Leaf area index is a promising parameter that may show comparative characteristics of ILTER sites on the global scale. When LAI is measured at a forest ecosystem, LI-COR LAI-2000 is frequently used but relatively expensive and requires open space to measure reference solar radiation. Alternatively, some forest scientists prefer a multi-purposes, consumer-grade digital camera that provides an upward-looking view of forest canopy. Unlike LAI-2000, it is cheap, handy and captures digital images directly. However, little is known about their processing with HemiView software (Canopy analysis software ver.2.1, Delta-T Ltd.) that is necessary to analyze digital canopy images. HemiView software adopts a threshold method in distinguishing canopy opening from foliage. The method has one problem, because LAI estimates depend on threshold values, which are inputted based on researcher's experience. Hence, we examined an approach to solve the problem. First, we obtained hemispheric digital images (Nikon Coolpix 900 with LC-ER1 fisheye) and LAI values using LAI-2000 at a KLTER site (Gwangneung Experimental Forest) for a year. Second, similar data were collected at a same site in the daytime, while bright was varied. Then, we tuned thresholds so that fisheye LAI values were consistent with LAI-2000 ones, and related the consequences to the field condition when the images were acquired. In the first experiment, thresholds were mainly varied with weather conditions such as cloud cover fraction and solar radiation. Thresholds were lower in a coniferous forest than in a deciduous forest except for winter season. In the second experiment, thresholds were positively correlated with interior brightness of canopy at the time of image capture. Finally, we propose a method to set reliable thresholds for data collected from different types of forests and under various light conditions. The result will be instrumental in comparing ground truths and remote sensing data of LAI over ILTER sites.

Participatory Inventory and Assessment of Floral Resources and Livelihood Development in Malindang Range, Mindanao, Philippines

Date Presented: Friday Night

Lead Author: Victor B. Amoroso
Co-Authors: Jose B. Arances, Lilibeth V. Rufila
Institutional Affiliations: Central Mindanao University
Primary Site: INT

Abstract: Involving the participation of the Subanons as local researchers, an assessment of plant diversity in a two 1-hectare semi-permanent plots located in Mt. Ginanlajan and Palo 6, Malindang Range revealed 285 species, 177 genera and 109 families. The scientific identification of plants was enriched by the local indigenous knowledge. Complete inventory of trees showed high species richness (63-67 species/ha) and high tree density (961-1,000 /ha) per hectare. These figures are higher than that reported for lowland and montane forests in Mt. Kitanglad and other neotropical countries. Assessment of floral resources also revealed 2 endangered species, 71 endemic species, 11 rare and 171 economically important species and 10 species of socio-cultural importance. Endemism is high since of the 85 species of trees, 48 (57%) are endemic. A noteworthy finding is the discovery of three species of mosses which are new records in the Philippines. As a result of participatory inventory assessment and community validation meeting, the local researchers/Subanens have identified the establishment of Nursery by utilizing fast growing trees and Community Economic Garden as potential livelihood projects for biodiversity conservation.

Partitioning of Mineralized Nitrogen in Subtidal Sediments of Hog Island Bay, a Shallow Coastal Lagoon on Virginia’s Eastern Shore

Date Presented: Saturday Night

Lead Author: Frank M Parker III
Co-Authors: Iris C Anderson, Karen McGlathery
Institutional Affiliations: Virginia Institute of Marine Science, University of Virginia
Primary Site: VCR

Abstract: The ability of shallow coastal lagoons to remove or transform nutrients during their transport across the land-sea margin depends largely on the degree of benthic–pelagic coupling in the system. Decoupling of sediment biogeochemical processes from water column processes may occur due to uptake and transformation of nutrients by benthic micro- and macroalgae, removal of nutrients by coupled nitrification–denitrification, immobilization into bacterial biomass, and trophic transfer. We have performed a series of experiments in Hog Island Bay, a shallow coastal lagoon on Virginia’s Eastern Shore, in order to determine the major fates and the relative magnitudes of the processes driving nitrogen cycling within subtidal sediments. Our results show that sediment remineralization is the major source of N supporting coupled nitrification-denitrification and benthic microalgal N-demand. However, we are unable to partition the remineralized nitrogen between these two major fates. In order to address that we are planning a series of dual label stable isotope tracer (¹³DIC and ¹⁵DIN) experiments. These experiments will include uptake into the various sediment pools and dilution through recycling of C and N, and should provide a better estimate of BMA N-demand relative to C.

Patterns and causes of variation in NPP in the giant kelp, Macrocystis pyrifera

Date Presented: Saturday Night

Lead Author: Andrew Rassweiler
Co-Authors: Katie Arkema, Dan Reed, Dick Zimmerman
Institutional Affiliations: University of California, Santa Barbara; Moss Landing Marine Laboratories
Primary Site: SBC

Abstract: The giant kelp, Macrocystis pyrifera, is the world’s largest alga and is believed to be one of the fastest growing autotrophs on earth. In southern California, M. pyrifera biomass fluctuates greatly in time and space, responding to the complex nature of predictable (seasonal) and unpredictable (aseasonal) events. To better understand this variability, we initiated field studies designed to examine spatial and temporal patterns of variation in the production of giant kelp, and the factors that control them. Net primary production (NPP) of giant kelp is estimated monthly at three sites in the Santa Barbara Channel from measurements of changes in the size of individuals, stand density, and rates of frond turnover. NPP averaged nearly 4 g C /m2/d at the three sites during 2002. Variation in NPP was explained in large part by standing crop, which decreased at all sites in the fall when nutrient concentrations decreased and storm activity increased. Changes in biomass were driven primarily by losses of adult individuals during storms. Such density-independent losses caused the peaks in growth and NPP to occur out of phase.

Patterns in Belowground Primary Productivity in the Oligohaline Ecotone of Taylor Slough and Shark River Slough, Florida

Date Presented: Friday Night

Lead Author: Gregory M. Juszli
Co-Authors: Daniel L. Childers
Institutional Affiliations: Florida International University
Primary Site: FCE

Abstract: Patterns of primary productivity in the Florida Everglades are controlled by changing freshwater inputs into the system. Existing productivity data in the main ecotone region of the Everglades, the region where P deficient Everglades freshwater meets marine waters with relatively higher P, reveal different dynamics between the two major drainage basins of Everglades National Park, Shark River Slough and Taylor Slough. A productivity peak exists in the ecotone region of Shark River Slough that is not evident in Taylor slough. This experiment focuses on the effects of landscape location and nutrient enrichment on patterns and magnitudes of belowground primary productivity (BPP). Cladium jamaicense, the dominant freshwater macrophyte in each slough, will be used to assess a value for BPP based on measurements of root biomass at sites within the olighaline ecotone of each basin. Additionally, this study will test the hypothesis that Cladium jamaicense responds to variation in nutrient availability by altering its biomass allocation. Cladium BPP estimates should reveal seasonal patterns, variation along the salinity gradient of the ecotone, variation between the sloughs, and nutrient enrichment responses. BPP values should be relatively lower in Cladium sampled from the southern sites due to elevated salinity levels. Similarly, Shark River Slough should exhibit relatively lower BPP than Taylor Slough due to the increased P availability in that slough. Also, because N and P are both potentially limiting in the ecotone, nutrient enrichment with both N and P should produce relatively lower BPP, as well as a higher above:belowground biomass ratio, compared to treatments with one of these nutrients . The results of this experiment will be particularly important as freshwater inflows increase into the marine-freshwater ecotone as part of the Everglades Restoration Project.

Patterns of Primary Production in a Coastal Lagoon: Implications for Nitrogen Retention and Turnover

Date Presented: Saturday Night

Lead Author: Karen McGlathery
Co-Authors: Kim Holzer, Mads Thomsen, Christy Tyler, Peter Berg
Institutional Affiliations: University of Virginia
Primary Site: VCR

Abstract: Coastal lagoons, like all estuaries, act as a filter removing or temporarily retaining nutrient inputs from the watershed on their trajectory from land to sea, and as such, may offer protection to the coastal ocean from eutrophication. Nutrient retention in these systems depends on rates of assimilation and turnover by primary producers and on permanent losses via denitrification and burial, as well as on water residence times. We determined seasonal variation in biomass for the dominant plant groups (macroalgae, benthic microalgae, phytoplankton) in a coastal lagoon on the eastern shore of Virginia and estimated nitrogen assimilation and turnover for the different groups using monthly-bimonthly estimates of biomass and C:N content, growth rates and oxygen metabolism. We then constructed a model to account for light attenuation both within and between primary producer groups to calculate areal nitrogen assimilation and turnover, and scaled this to the entire lagoon. We will describe the variation in the role of the different plants groups as temporary nitrogen sinks within the lagoon and the implications for nitrogen retention over seasonal and annual time scales.

Persistent Organic Pollutants in Antarctic Air

Date Presented: Saturday Night

Lead Author: Alessandra Cincinelli
Co-Authors: Hugh Ducklow and Rebecca M. Dickhut
Institutional Affiliations: Virginia Institute of Marine Science
Primary Site: PAL

Abstract: Various persistent, bioaccumulative toxic pollutants such as organochlorine pesticides have been measured in the Antarctic marine food web. The introduction of such contaminants into the Antarctic marine ecosystem is thought to be due to long-range atmospheric transport and deposition due to a lack of point source pollution on the Antarctic continent. In an effort to link the atmospheric transport and deposition of persistent organic pollutants (POPs) to the bioaccumulation of POPs at the base of the Antarctic marine food web, high volume air samples were collected along the Antarctic Peninsula in addition to seawater, snow/sea ice, and phytoplankton/SIMCO (sea ice microbial community) samples during both the austral summer and winter. An abundance of HCB was observed in Antarctic air along with the presence of hexachlorocyclohexanes, heptachlor, and dieldrin.

Plague epizootics in prairie-dog colonies associated with El Niño climatic events

Date Presented: Saturday Night

Lead Author: Paul Stapp
Co-Authors: Mark Ball, Michael Antolin
Institutional Affiliations: Californai State Unviersity - Fullerton; U.S. Forest Service; Colorado State Unvieristy
Primary Site: SGS

Abstract: Outbreaks of many vector-borne human diseases are broadly correlated with climatic variation, but evidence of similar fluctuations in disease in natural animals host populations is rare. We analyzed 21 years of monitoring of prairie-dog (Cynomys ludovicianus) colonies to demonstrate a link between extinctions of colonies attributed to plague (Yersinia pestis) and climatic fluctuations associated with El Niño Southern Oscillation events that could promote the growth of flea vector and rodent host populations. The largest and smallest colonies suffered the highest rates of extinction (>60%) during outbreaks, and the probability of extinction was influenced by the size and fate of adjacent colonies. There was no predictable relationship, however, between extinction probabilities and inter-colony distance, indicating that spatial isolation does not reduce the vulnerability of colonies to plague. By causing sporadic extinctions of colonies, plague promotes a metapopulation structure that has changed the dynamics of prairie-dog colonies as they respond to a century of human persecution and anthropogenic habitat loss.

Planning for resilience: modeling change in human-fire interactions in the Alaskan boreal forest

Date Presented: Friday Night

Lead Author: F. Chapin
Co-Authors: Scott Rupp, Amy Lovecraft, Anthony Starfield, La-ona DeWilde, David McGuire
Institutional Affiliations: University of Alaska, University of Minnesota
Primary Site: BNZ

Abstract: The development of policies that promote ecological, economic, and cultural sustainability and resilience requires a framework that incorporates human activities as integral components of social-ecological systems. We present a conceptual model of role of human activities (ignitions and suppression) on the interactions between climate, wildfire and vegetation in interior Alaska. Policy scenarios based on this conceptual model are then used as inputs to a landscape model that simulates the long-term impacts of fire regime on vegetation. Simulations suggest that fire suppression is likely to increase the proportion of flammable vegetation on the landscape, reduce the long-term effectiveness of wildfire suppression, and reduce the resilience of the human-fire-vegetation system. The use of simple models to test the consequences of assumptions provides a vehicle for objective communication between natural and social scientists to explore the long-term consequences of alternative policy scenarios.

Plant species influence on N₂O and NO_x gas emissions from soils

Date Presented: Saturday Night

Lead Author: Terry Loecke
Co-Authors: G. Phil Robertson
Institutional Affiliations:

Abstract: Soils are major anthropogenic sources of nitrous oxide (N₂O), a potent greenhouse gas, and of nitric oxide (NO_x), an important component of acid deposition and photochemical smog formation. Greater than 50% of all anthropogenic emissions of N₂O are from agricultural soils. The Intergovernmental Panel on Climate Control’s National Inventory Guidelines assume that N₂0 gas fluxes from soils are independent of crop species despite a lack of empirical data to support this assumption. The influence of individual plant species on nitric oxide gas fluxes is largely unknown. It is known, however, that plant species differentially influence the most proximal controls on these gas fluxes (soil O₂, NH₄⁺, and NO₃^{- concentrations and carbon availability). Due to their global extent and well characterized biology crop species are good models for studying these effects. By examining soils planted to soybean, corn, and wheat cropped in rotation and continuous cultivation we hope to estimate the N₂O and NO_x gas fluxes as influenced by the current and previous crop species grown in that soil. Preliminary studies are underway to address these questions.}

Plant traits and resource competition: controls on prairie plant abundances

Date Presented: Friday Night

Lead Author: Joe Fargione
Co-Authors: David Tilman
Institutional Affiliations: University of Minnesota
Primary Site: CDR

Abstract: The abundance of plant species competing for nitrogen may be explained by the efficiency of their nitrogen acquisition and use. Because (polyculture biomass) = (monoculture biomass) * (relative yield), we suggest that the question of what controls species’ biomass in polyculture can be decomposed into two more tractable questions: (1) what controls biomass in monoculture? (2) What controls relative yield? We measured plant traits of 21 non-leguminous plants in 105 three-year-old 1 x 1 m monocultures. We estimated relative yield using data from a long-term biodiversity experiment, where relative yield was calculated as (polyculture biomass)/(monoculture biomass). Total monoculture biomass (above + belowground biomass) was predicted by the inverse tissue nitrogen concentration (of above and belowground plant tissues), i.e. the amount of biomass produced per unit nitrogen, a measure of the efficiency of nitrogen use. Relative yield was predicted by root length density (the length of roots per volume of soil), a measure of the efficiency of nitrogen acquisition. This is consistent with existing theory and experiments which show that nitrogen acquisition is proportional to root length density. Our results suggest how simple plant traits associated with mechanisms of resource competition may be used to predict the abundances of competing species.

Porewater Stoichiometry of Terminal Metabolic Products, Sulfate, and Dissolved Organic Carbon and Nitrogen in Estuarine Sediments

Date Presented: Friday Night

Lead Author: Nat Weston
Co-Authors: Samantha Joye, William Porubsky, Vladamir Samarkin, Matthew Erickson
Institutional Affiliations: University of Georgia
Primary Site: GCE

Abstract: Porewater equilibration meters were used to obtain porewater inventories of inorganic nutrients (N, P) dissolved organic carbon (DOC) and nitrogen (DON), sulfate (SO₄^2-), chloride (Cl^-), and reduced metabolites in estuarine sediments at eight sites in three estuarine systems over a range of salinities and seasons. Sulfate reduction (SR) rates and sediment particulate organic carbon (POC) and nitrogen (PON) were also determined at several of the sites. The large data set (nearly 20,000 individual data points) offers a unique opportunity to assess spatio-temporal patterns of porewater biogeochemical species in estuarine sediments. SO₄^2- depletion (SO₄^2-)dep was used as a proxy for SR. We observed remarkable correlations between the inorganic products of terminal metabolism (DIC, NH₄⁺, PO₄^3-) and (SO₄^2-)dep, suggesting the dominant terminal carbon oxidation pathway in these sediments was SR. Seasonality was observed in the porewater inventories, suggesting temperature in part controlled metabolic rates, but temperature alone did not adequately describe the patterns of (SO₄^2-)dep, terminal metabolic products, dissolved organic carbon and nitrogen, and SR we observed. The data suggest that production and consumption of DOC are tightly coupled in these sediments, and that bulk DOC is a recalcitrant pool. Preferential hydrolysis of PON to DON when overall organic matter mineralization rates were high appeared to drive the observed patterns in POC:PON, DOC:DON and DIC:NH₄⁺ ratios. These data, along with the weak seasonal patterns of SR and porewater inventories, suggest that hydrolysis rates limited organic matter mineralization.

Preliminary Findings in a 15N Tracer Addition Mesocosm Experiment

Date Presented: Friday Night

Lead Author: Jeffrey R. Wozniak
Co-Authors: Daniel L. Childers, William T. Anderson
Institutional Affiliations: Florida International University and Florida Coastal Everglades LTER
Primary Site: FCE

Abstract: This project will analyze the effects of the hydrologic restoration of the Southern Everglades on the nutrient dynamics of the exosystem by quantifying the nitrogen cycle in the region via stable isotope tracer techniques. Before this project can be fully implemented, a pilot study is necessary to consider sample methodology, logistics, and sample schedule; this poster will address the results from the pilot study. By utilizing 15N tracer techniques, quantification of several ecosystem processes, including N fluxes between periphyton-water column, soil-water column, and soil-macrophyte interactions were possible. Th