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United States Department of Agriculture

Agricultural Research Service


Location: Rangeland Resources Research

2011 Annual Report

1a. Objectives (from AD-416)
Evaluate how warming and increasing atmospheric CO2 concentration affect the structure and functioning of Great Plains grasslands through their affects on primary production, N and C cycling, water relations, and plant community dynamics.

1b. Approach (from AD-416)
Stable Isoptope Lab/University of Wyoming (SILUW) and ARS will collaborate in planning and conducting cooperative global change research at the High Plains Grasslands Research Station (HPGRS) to investigate how global change influences ecosystem functioning through evaluating the combined effects of rising atmospheric CO2 and temperature on C and N cycling, plant/soil water relations, weed invasions and plant community ecology. Research will be conducted under realistic field conditions in a native, semi-arid grassland in which ambient CO2 is increased from present-day levels of 390 ppm to 600 ppm and temperatures increased 1.5/3 C day/night. These altered environmental conditions are predicted to develop in Wyoming over the second half of the century.

3. Progress Report
University of Wyoming collaborators are working with ARS to increase our understanding of how soils and plants respond to global warming, rising CO2, and altered precipitation, as part of a comprehensive research project predicting how western rangelands will respond to climate change. We are in the 6th year of the Prairie Heating and CO2 Enrichment (PHACE) experiment. Work on the PHACE project led by the UW research teams continues to evolve and expand. UW collaborator submitted two large research proposals to continue below ground studies on C and N dynamics, and both have been recommended for funding. The NSF-Ecosystems grant started in Sept., 2010, and examines plant-microbe feedback mechanisms related to C and N cycling. The DOE-TCP grant is expected to start by October, 2011, and provides funding for continuation of the experimental treatments through the summer of 2013, in addition to modeling. A proposal by UW collaborator and his postdoc was recommended for funding by the UW NASA Space Grant Consortium to begin examining how plant invasion alters ecosystem water and carbon exchange. The University of Wyoming Stable Isotope Facility (UWSIF) will continue to provide expertise and analyses for the PHACE project. In addition to continuing work on C cycling in native mixed-grass prairie using stable isotopes at PHACE, a UW collaborator's group has expanded their research questions to the role of invasive species in mediating C and N cycling by measuring net ecosystem exchange (NEE), evapotranspiration (ET) and soil biogeochemical processes within the “weeds” portion of the PHACE experiment. Additional, species-specific experiments have been conducted outside the PHACE plots using stable isotope tracer techniques. The Williams Rangeland Plant Ecophysiology Lab (RPEL) at UW continues to contribute to the PHACE project with studies on leaf to whole plant photosynthetic and water relations responses and N uptake patterns and by supporting NEE and ET measurements led by a UW collaborator’s group and focusing on leaf photosynthetic biochemistry, leaf gas exchange, plant water relations, leaf isotopic discrimination analysis and N uptake and utilization patterns in an effort to characterize plant responses to warming, CO2 enrichment and experimental irrigation, and to upscale leaf gas exchange to the ecosystem level. New studies are planned in the final three years of this experiment to evaluate how global change treatments effect plant respiration as well as studies on longterm stomatal responses to CO2 warming. The ADODR holds meetings every 6 months with UW collaborators to discuss research and site issues. Staff of both groups communicate regularly on experimental protocols, site management, and presentation of results. The group continues to coordinate on modeling and data base management efforts so the results of this work can be extrapolated by modeling projects involving project scientists and potential future collaborators.

4. Accomplishments

Last Modified: 06/26/2017
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