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Harvard Forest Symposium Abstract 2011

  • Title: Multiyear Applications of 14C-Enriched Leaf Litter at Temperate Deciduous Forests Across the Eastern United States: Application to Direct Observations of Soil Carbon Transport and Storage Dynamics In Organic and Mineral Soils
  • Primary Author: Paul Hanson (Oak Ridge National Laboratory)
  • Additional Authors: Mac Callaham (USDA Forest Service); Tom Guilderson (Lawrence Livermore National Laboratory); Julie Jastrow (Argonne National Laboratory); Roser Matamala (Argonne National Laboratory); Karis McFarlane (Lawrence Livermore National Laboratory); William Parton (Colorado State University); Margaret Torn (Lawrence Berkeley National Laboratory); Susan Trumbore (University of California - Irvine)
  • Abstract:

    Interannual dynamics of litter and soil C pools are not well defined. Much data are now available for CO2 efflux from soils, but the net effect of such fluxes on C stocks residing in soils is seldom quantified. A multiyear, multisite study was initiated in 2007 to use unique 14C-enriched materials to characterize the rate of C flux from litter sources to mineral soil sinks over a range of climatic and biological conditions. The Enriched Background Isotope Study focusing on AmeriFlux Sites (EBIS-AmeriFlux) provides quantitative data on the rate of C flux from litter sources to mineral soil sinks for United States eastern hardwood forests. These data are applicable for testing process-level hypotheses and judging the efficacy of soil C cycling models. We have been utilizing 14C-enriched material from local releases of radiocarbon resulting in whole-ecosystem isotopic label near Oak Ridge, Tennessee to study issues associated with the terrestrial soil carbon cycle. In 2004 and 2005, new atmospheric pulses of 14CO2 led to biological enrichment of additional plant material on the Oak Ridge Reservation (ORR). These 14C inputs and the 14C-enriched plant material generated from them provided the opportunity to undertake soil carbon cycle studies along a climatic gradient of AmeriFlux hardwood sites.

    We are executing an experimental plan designed to use 14C-enriched leaf and root litter and humus at multiple AmeriFlux sites for the direct characterization of leaf litter transfers to mineral-soil sinks over a range of climatic and biological conditions across the eastern United states. The experimental data generated by the EBIS-AmeriFlux effort together with conclusions from the preceding EBIS-Oak Ridge study will provide a key contribution to databases on soil carbon cycling processes for use in evaluating the next generation of terrestrial carbon models. Those models are needed in the ongoing evaluation of terrestrial ecosystem’s role in the global carbon cycle. This proposed 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.

  • Research Category: Regional Studies
    Soil Carbon and Nitrogen Dynamics