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United States Department of Agriculture

Agricultural Research Service


Location: Rangeland Resources Research

2010 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
Collaborating UW scientists 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 midway through the Prairie Heating and CO2 Enrichment (PHACE) experiment. Work on the PHACE project led by the UW research teams is progressing rapidly. The collaborative engagement between two UW research groups on this project continues to evolve and expand. One UW scientist submitted two large research proposals to continue below ground studies on C and N dynamics, and one, the NSF ETBC proposal has been recommended for funding. A proposal by a UW scientist 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; technical difficulties in analyzing high 15N enrichment values for PHACE samples have been remedied. Research activities by the UW teams for the PHACE project during the period from October 2009 to present involved 4 undergraduate technicians, 3 graduate students, 2 postdocs and 2 senior faculty scientists. In addition to continuing work on carbon cycling using stable isotopes at PHACE, a UW scientist group conducted a growth chamber experiment to test the role of mycorrhizae in affecting nutrient uptake under elevated CO2. This experiment involved development of new infrastructure at the Crops Lab in Fort Collins to provide isotopic labeling of both ambient and elevated CO2 conditions. Additionally, new 15N labeling techniques were developed. Preliminary results from this project are forthcoming. Another UW scientist's 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. A UW lab's work focuses on leaf photosynthetic biochemistry, leaf gas exchange, plant water relations, leaf isotopic discrimination analysis and N uptake and utilization patterns, all in an effort to characterize plant responses to warming, CO2 enrichment and experimental irrigation, as well as to upscale leaf gas exchange to the ecosystem level. With leveraging from the University of Wyoming Stable Isotope Facility, the another UW lab has led studies on leaf carbon isotope discrimination. To ensure accountability of funds utilized, the ADODR and his staff hold meetings every 6 months with UW collaborators to discuss research and site issues; staff of both groups communicates regularly on experimental protocols, site management, and presentation of results.

4. Accomplishments

Last Modified: 06/28/2017
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