HR: 15:10h
AN: B53D-06    [Abstracts]
TI: Carbon Structural Investigations of Concentric Layers Within Macro-aggregates From Forest and Agricultural Soils
AU: * Dria, K J
EM: kdria@purdue.edu
AF: Purdue University, Department of Earth and Atmospheric Sciences 550 Stadium Mall Dr. , W. Lafayette, IN 47907-1397 United States
AU: Gamblin, D E
EM: gamblind@purdue.edu
AF: Purdue University, Department of Earth and Atmospheric Sciences 550 Stadium Mall Dr. , W. Lafayette, IN 47907-1397 United States
AU: Smucker, A J
EM: smucker@msu.edu
AF: Michigan State University, Department of Crop and Soil Sciences , East Lansing, MI 48824-1325 United States
AU: Park, E
EM: parkeun2@msu.edu
AF: Michigan State University, Department of Crop and Soil Sciences , East Lansing, MI 48824-1325 United States
AU: Filley, T R
EM: filley@purdue.edu
AF: Purdue University, Department of Earth and Atmospheric Sciences 550 Stadium Mall Dr. , W. Lafayette, IN 47907-1397 United States
AB: Much of the current research on the potential of agricultural and forest soils to act as sinks for greenhouse gases focuses on the capacity of the systems to form long-term stabilized fractions of soil organic matter (SOM). One proposed mechanism is that carbon is sequestered within soil aggregate interiors during the aggregation process. Repeated wetting-drying cycles change internal pore geometries and associated microhabitats and create more stable macro-aggregates. Research by Smucker and coworkers (EGU Abstracts, 2004) suggest that the exterior portions of aggregates contain greater concentrations of C and N than their interiors, establishing gradients of \„13C values across these aggregates. We present the results of a study to test if there exists molecular evidence of such gradients. Soil samples from forest, conventional tillage (CT) and no tillage (NT) agriculture ecosystems in Hoytville and Wooster LTER sites were gently sieved into various size fractions. Soil macro-aggregates (6.3-9.5mm) were peeled, by mechanical erosion chambers, into concentric layers and separated into exterior, transitional and interior regions. Alkaline CuO oxidation was used to determine the composition of lignin, suberin, and cutin biopolymers to determine changes in source and degradative states of SOM. Preliminary results indicate that both soils show similar relative yields of lignin and hydroxyl fatty acids with a greater abundance of lignin than cutin and suberin acids. Greater abundances (per 100mg organic carbon) of CuO products were observed in the native forest than in either agricultural system. The lignin in the NT agricultural soil was least oxidized, followed by the forest soils, then the CT agricultural soils. For both soils, slight trends in biopolymer concentrations were observed between the exterior, transitional and interior regions of the aggregates from the forest and CT or NT ecosystems.
DE: 1030 Geochemical cycles (0330)
DE: 1055 Organic geochemistry
DE: 1094 Instruments and techniques
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting