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Harvard Forest Symposium Abstract 2011

  • Title: Decadal-Scale Changes in Soil Carbon at Harvard Forest: Insights From Radiocarbon Measurements and Modeling
  • Primary Author: Carlos Sierra (Max Planck Institute for Biogeochemistry)
  • Additional Authors: Eric Davidson (University of Maryland - Center for Environmental Science); Serita Frey (University of New Hampshire - Main Campus); Kathleen Savage (Woods Hole Research Center); Susan Trumbore (University of California - Irvine)
  • Abstract:

    Changes in climate at decadal and centennial time scales can potentially alter the amount of carbon stored in forest soils. There is uncertainty however, on the quantity and the quality of soil carbon that can be destabilized and released to the atmosphere by changes in climate and other environmental conditions. Ongoing measurements of radiocarbon at Harvard Forest are being used to assess the degree to which changes in environmental factors can modify the decadal-scale carbon balance in these soils.

    Empirical and mechanistic models that synthesize existing data on the functioning of soil organic matter decomposition are being challenged with new measurements taken at different sites in Harvard Forest. In particular, a seven-pool empirical model developed a decade ago was used to predict current radiocarbon fluxes. It was found that this model performs exceptionally well under current conditions, as opposed to other models with different pool structures. A three-pool model parameterized with the same data used to parameterize the seven-pool model, fails to predict current radiocarbon fluxes. In addition to current fluxes, these models are being challenged with radiocarbon measurements from the warming, fertilization, and litter addition experiments. Radiocarbon measurements suggest that the age of the respired carbon differs in the warming and nitrogen addition treatments. This response however, was only detectable after 5 years of manipulations. These results suggest that carbon of different qualities respond differently to warming and nitrogen fertilization, but at rates that are only detectable at decadal time-scales.

  • Research Category: Soil Carbon and Nitrogen Dynamics