The soil carbon reservoir outweighs the carbon in living plants, the atmosphere, or fossil fuel emissions. This study tests the effects of a future climate change, increased rainfall, on soil carbon quality in a California annual grassland. One possible outcome of increased rainfall in this ecosystem is increased soil microbial respiration (conversion of soil carbon to carbon dioxide by soil microorganisms), leaving behind carbon more resistant to degradation. Two techniques, applied in the laboratory and the field, will track this process. First, soil carbon will be fractionated: separated into light or heavy fractions based on density. Second, radiocarbon analysis will be used to determine a turnover rate (how fast soil carbon is converted to carbon dioxide) for each fraction. These techniques may detect changes in soil carbon quality even if no changes are seen in total soil carbon quantity. This study will enhance our understanding of rainfall effects on carbon cycling and budgets.
