HR: 0800h
AN: B11A-1017    [Abstracts]
TI: Uncertainties on Root C Turnover and Decomposition and its Impact on Soil C Sequestration Potential
AU: * Matamala, R
EM: matamala@anl.gov
AF: BioSciences Division, Argonne National Laboratory, 9700 S. Cass Ave, Argonne, IL 60439 United States
AU: Gonzalez-Meler, M A
EM: mmeler@anl.gov
AF: Department of Biological Sciences, University of Illinois at Chicago, Taylor Street, Chicago, IL 60607 United States
AU: Jastrow, J D
EM: jdjastrow@anl.gov
AF: BioSciences Division, Argonne National Laboratory, 9700 S. Cass Ave, Argonne, IL 60439 United States
AB: Roots provide a path for movement of carbon and energy from plant canopies to soils; thus, root production and turnover directly impact the biogeochemical cycle of C and nutrients in terrestrial ecosystems. Uncertainties in estimates of production, mortality and decomposition of roots prevent proper quantification of net primary productivity (NPP), belowground C allocation and inputs to soil organic matter. Our study compares the ecosystem C sequestration potential of two distinct forest types, a pine and a sweetgum forest, growing under FACE (Free Air CO2-Enrichment) conditions that allow for the use of 13CO2 as a tracer in the tissues and soils. Using this technique root C turnover measurements have showed that although fine roots have often been assumed to have MRT of about one year, the MRT of the fine root C varies from 1 to 9 years depending on root diameter and tree species. The relative importance of a slow or a fast root C turnover is shown on the C accrual rate of the soil, slow root turnover rates appears to reduce the sequestration potential of C in soil supporting pine trees, while fast root C turnover in a sweetgum forest sustained significant increases in soil C after being exposed to elevated CO2 for five to six years. The rate of root decomposition and root inputs are calculated for both forest types and compared with the rate of soil organic matter accrual. Our results suggest that C sequestration in soils is strongly affected by root production and the MRT of C of the root system.
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
SC: Biogeosciences [B]
MN: Fall Meeting 2005