380-8 Belowground Carbon Turnover and Ecosystem Carbon Dioxide Source Attribution: A Radiocarbon-Based Approach.



Wednesday, October 19, 2011
Henry Gonzalez Convention Center, Hall C, Street Level

Karis McFarlane and Claire Phillips, 7000 East Ave, L-397, Lawrence Livermore, Livermore, CA
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How the net uptake of atmospheric CO2 concentration by forests will respond to future changes in climate and land-use is not well understood. Across deciduous broadleaf forests, variations in soil respiration (RS) explain much of the spatial and inter-annual variability in net ecosystem exchange (NEE). RS is likely to be influenced by climate and land-use change, but prediction of future changes is challenged by difficulty in modeling fluxes over space and time. One challenge is that RS includes CO2 released via autotrophic (root) respiration and heterotrophic (microbial) respiration, very different processes that respond to temperature and moisture differently, and are likely to respond asymmetrically to future changes in climate and ecosystem characteristics. In addition, changes in climate or land-use that favor microbial activity may change C sources used by microbes (e.g. cause priming of stable soil C).

Our goal is to determine the short-term effects of forest management on RE and RS fluxes in a mature northern hardwood forest and to attribute changes in the regional biosphere signal of atmospheric 14CO2 to this disturbance using 14C as an isotopic tracer. Eddy covariance methods can be used to estimate bulk CO2 fluxes but they cannot discriminate process nor C source of respired CO2. It is these processes, which are parameterized in predictive models and may change with future climate and land-use change that our observations address. We are comparing observations of 14C in CO2 fluxes and soil organic matter pools of varying turnover time made before and after selective harvest for a well studied region to determine which belowground carbon pools contribute to changes in overall ecosystem C storage and flux following management induced disturbance. Our approach and preliminary pre-treatment results will be presented.

See more from this Division: S07 Forest, Range & Wildland Soils
See more from this Session: General Forest, Range and Wildland Soils: II