Characterizing Organic Carbon Flux from Litter Sources to...

Characterizing Organic Carbon Flux from Litter Sources to Mineral-Soil Sinks (1)Enriched Background Isotopic Study (EBIS) Closure, and (2) Establishment of a Distributed Enriched Isotope Study for AmeriFlux Hardwood Forests This research provides data on C flux from litter sources to mineral soil sinks for United States eastern hardwood forests necessary for testing process hypotheses and judging efficacy of soil C cycling models. EBIS utilizes releases of radiocarbon resulting in a whole-ecosystem isotopic label near Oak Ridge, Tennessee to study issues associated with the terrestrial soil carbon cycle. EBIS observations support conclusions that intra- and inter-annual soil carbon cycling in hardwood forest soils be characterized as a two-compartment system where surface leaf-litter and belowground root turnover represent primary carbon sources for organic-layer and mineral-soil carbon cycles, respectively. New experiments are planned to (1) achieve completion of EBIS observations in Oak Ridge, (2) collect update 14C-enriched materials for experimental applications, and (3) apply those materials to multiple AmeriFlux sites over a range of climatic and biological conditions. The experimental data generated by EBIS will contribute to a detailed database for evaluating the next generation of terrestrial carbon models and resolve uncertainties about C fates within AmeriFlux study site soils. The research provides data for addressing DOE's goal of understanding mechanisms controlling C flux, and for the improvement of models to be applied to policy discussions regarding the safe levels of greenhouse gases for the earth's system. Future work on fundamental soil carbon cycling processes at the EBIS-AmeriFlux sites will be continued as a part of the update Science Focus Area on Climate Change Forcing (ERKP720) in FY09 and beyond.