2007 Annual Report 1a.Objectives (from AD-416) Investigate the manipulation of terrestrial ecosystems which can offset human induced carbon emissions to the atmosphere for the next 40 years by sequestering additional amounts of carbon in soils and vegetation. 1b.Approach (from AD-416) Develop field experimental protocol to evaluate the spatial variability of C storage in soils under different regimes. Develop protocol for chemical fractionation of soil carbon pools that will delineate the effects of climate on carbon storage. Develop predictive interpretation methodology for describing carbon compartmentalization as a function of changing climate. Develop N-15 pool dilution technique to quantify nitrogen pools and processes in soils under different climatic regimes and the effect on C storage. Documents Reimbursable with DOE. Log 28341. Formerly 5348-11120-002-03R (5/06). 3.Progress Report This report serves to document research conducted under a reimbursable agreement between ARS and Department of Energy. Additional details of research can be found in the report for the parent project 5348-11120-004-00D, Soil conservation systems for sustainability of Pacific Northwest agriculture. Soil carbon (C) storage is important for maintaining healthy soil and has recently been recognized as a means to reduce carbon dioxide (CO2) emissions from the burning of fossil fuels. However, global warming could reduce the potential for soils to retain C and even contribute CO2 to the atmosphere. We are investigating the potential for soils to lose C if the atmosphere does increase in temperature. In one study we transplanted soils from a warmer climate (900 ft elevation) to a cooler climate (2700 ft elevation) and cores from the 2700 ft elevation down to the 900 ft elevation, representing a 10oF change in temperature. After 5 years the soils that were moved from the cooler climate to the warmer climate lost 32% of the total soil C and 40% of the total soil nitrogen (N). Much of this loss was from an active component of soil organic matter critical to soil functioning. This suggests that with warmer and drier conditions soil C could contribute to increased atmospheric CO2 and decrease enough to cause an alteration to ecosystem diversity and function. This reimbursable agreement was assessed through regular meetings and site visits. 4.Accomplishments None 5.Significant Activities that Support Special Target Populations None