HR: 09:00h
AN: B51E-03    [Abstracts]
TI: Nature and Dynamics of Carbon Accrued in a Forest Soil During Five Years of Atmospheric CO$_{2}$ Enrichment
AU: * Jastrow, J D
EM: jdjastrow@anl.gov
AF: Argonne National Laboratory, Environmental Research Division, Argonne, IL 60439 United States
AU: O'Brien, S L
EM: sobrie1@uic.edu
AF: Argonne National Laboratory, Environmental Research Division, Argonne, IL 60439 United States
AU: Dria, K J
EM: kdria@purdue.edu
AF: Purdue University, Department of Earth and Atmospheric Sciences, West Lafayette, IN 47907 United States
AU: Moran, K K
EM: kmoran@anl.gov
AF: Argonne National Laboratory, Environmental Research Division, Argonne, IL 60439 United States
AU: Filley, T R
EM: filley@purdue.edu
AF: Purdue University, Department of Earth and Atmospheric Sciences, West Lafayette, IN 47907 United States
AU: Boutton, T W
EM: boutton@neo.tamu.edu
AF: Texas A&M University, Department of Rangeland Ecology and Management, College Station, TX 77843 United States
AB: The potential for enhanced soil C storage to partially offset rising atmospheric CO$_{2}$ concentrations is being evaluated by long-term field CO$_{2}$ enrichment experiments. Although plant productivity is often stimulated in such experiments, the fate of increased detrital inputs to soil has yet to be definitively resolved, in part because detecting changes in soil C against the relatively large, spatially heterogeneous pool of existing soil organic matter has proven difficult. Even when significant changes in whole soil C are evident, predictions of the potential for long-term sequestration will require detailed studies of C dynamics and stability in functionally meaningful soil organic matter pools. In our studies at the free-air CO$_{2}$ enrichment (FACE) experiment on a sweetgum ({\it Liquidambar styraciflua} L.) forest plantation in Oak Ridge, Tennessee, we are using (1) repeated sampling over time, (2) the isotopic tracer provided by the highly depleted $^{13}$C signature of the CO$_{2}$ source used for fumigation, and (3) physical and chemical fractionation procedures to determine the fate and dynamics of FACE-derived C inputs to soil organic matter. After five years of CO$_{2}$ enrichment, soil C accumulated at a linear rate in both unprotected and aggregate-protected pools, suggesting that additional C inputs were being processed and cycled in much the same manner as under ambient conditions. However, selective analysis of the biopolymer composition (lignin, suberin, and cutin) and oxidation state of the organic matter in physically and chemically isolated soil fractions will be used to assess the source, nature and potential stability of the C accrued in protected and unprotected pools.
DE: 1040 Isotopic composition/chemistry
DE: 1600 GLOBAL CHANGE (New category)
DE: 1615 Biogeochemical processes (4805)
DE: 0315 Biosphere/atmosphere interactions
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting