2008 Annual Report 1a.Objectives (from AD-416) The objective of this cooperative research project is to use stable isotopes and related ecological methods and technologies to elucidate the role of water relations, nutrient cycling, soil biology, and plant community responses to global change, and explore management options (e.g., legume additions) or issues (e.g., weed infestation) in the analysis and development of sustainable management practices for western rangelands. 1b.Approach (from AD-416) Although we know water and N are major drivers in the functioning of semi-arid rangeland plant communities, our knowledge of how to manage these lands in order to promote their sustainability and health through these important drivers is incomplete. Further, the constantly changing environment due to global climate change is altering water and nutrient cycles, independently causing important ecosystem changes and complicating our ability to understand and manage rangeland ecosystems. The Rangeland Resources Research Unit (RRRU) will conduct CO2 enrichment, grazing management, and legume research that will explore the consequences of combined global change and management on the structure and functioning of semi-arid rangelands. RRRU scientists will collaborate with scientists in the Stable Isotope Laboratory, University of Wyoming, to use stable isotope and related ecological methods and technologies to more fully explore the consequences of global change and management effects on ecological functioning of western rangelands. The results of these investigations will provide the basis for formulating new sustainable management strategies appropriate for the changing environment due to global climate change. 3.Progress Report Project participants during 2007-2008 included four grad students, five undergrads and one UW tech. 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. The primary setting for this research is the Prairie Heating and CO2 Enrichment Experiment, or PHACE, an experiment the USDA-ARS Rangeland Resources Research Unit has implemented in a natural prairie environment in south-eastern Wyoming with its collaborators at the UW and Colorado State University (CSU) for studying how increasing ambient CO2 and warming are affecting grassland ecology. CSU scientists are working with the ARS group in evaluating how critical soil and plant mechanisms respond to simulated climate change. The project is in its third year, and is moving forward in very significant and productive ways. During the growing seasons of 2007 and 2008, field measurements of the CSU Ecosystem Ecology group focused on plant canopy-scale measurements of the exchanges of carbon dioxide (CO2) and water, and plant cover by species. Measurements of how fast CO2 is being released from the soil were also made to help explain how climate change will affect the carbon balance of grasslands. Soil samples were collected in late July in 2006 and 2007, and will be analyzed for organic C and N content and related attributes. All of this information will be used to determine how plants and soils respond to CO2 and warming, and ultimately how the carbon balance of grasslands will be affected by climate change. This information is critical for predicting whether climate change will cause grasslands to release or store more carbon in the future. The Rangeland Plant Ecophysiology Lab at UW continues to contribute substantially to the PHACE project with studies on leaf to whole plant level physiological dynamics. The work in the lab is critical for understanding the basic physiological responses of plants to climate change that can affect their adaptability, and ultimately determine which plants species may prosper and which ones will diminish or disappear in the future. Preliminary results from these projects were presented this past year at meetings sponsored by the Ecological Society of America, the American Geophysical Union, and at the International Grasslands and Rangelands Congress. The ADODR and his staff hold meetings every six 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.