Tuesday, November 14, 2006 - 8:30 AM
183-2
Protection of Organic Carbon in Soil Microaggregates Occurs via Restructuring of Aggregate Porosity and Filling of Pores with Accumulating Organic Matter.
John McCarthy1, Jan Ilavsky2, Lawrence Mayer3, Julie Jastrow2, Edmund Perfect1, and Jie Zhuang1. (1) University of Tennessee, 306 Earth & Planetary Sci. Bldg., 1412 Circle Dr., Knoxville, TN 37996-1410, (2) Argonne National Laboratory, 9700S Cass Ave., Bldg. 438E, Argonne, IL 60439, (3) Darling Marine Center, 193 Clark's Cove Road, Walpole, ME 04573
The goal of this study is to determine the relationships between the dynamics of microaggregate structure and protection of soil organic matter within that structure. We used ultra-small angle x-ray scattering (USAXS) and took advantage of differenced in x-ray scattering by mineral and organic matter (OM) to evaluate the pore size distribution of the total- and OM-filled porosity within soil microaggregates. Systematic changes in aggregate structure were evaluated at two long-term field manipulations of land use (a chronosequence of tallgrass prairie restoration) and agricultural management (long-term till versus no-till cultivation at two levels of N inputs). Results emphasized the importance of the architectural system of aggregate packing in microaggregates to OM preservation. The source of OM protection appears to be filling of mineral pores with OM, which can create spatial and kinetic constraints on microbial access to and degradation of OM. The results have critical implications to the capacity for protection of OM in soil aggregates, and suggest that existence of important positive and negative feedback loops. We applied a new tool to obtain critical information on the mechanisms of OM protection, and demonstrated its effectiveness in evaluating strategies to enhance carbon sequestration in soil through changes in agricultural management practices and land use.