This proposed research aims to improve understanding of functional diversity of microbial populations and the influence of microbial diversity on carbon cycling in soils. Linkages between microbial community structure, functional diversity of microbes, and the relations of microbial community structure and diversity to soil carbon cycling will be explored using (1) measurements of the stable isotopic composition of soil organic matter fractions, (2) biomarkers specific to different microbial functional groups, and (3) microbially respired carbon. These approaches will also be used to evaluate microbial and carbon cycle responses to a changing atmosphere in creosote bush (chaparral) ecosystems under ambient and experimentally elevated CO2 at the Nevada Desert FACE (Free Air Carbon Enrichment) Facility. The information derived from this research could be of use in elucidating general principles of carbon-microbe interactions useful for understanding controls on soil biogeochemical processes in a range of ecosystem types in response to changing atmospheric CO2. The results could also improved ecosystem- and regional-scale estimates of carbon storage under elevated CO2.
