HR: 1330h
AN: H42C-1087    [PDF]
TI: Landscape Evolution and Carbon Accumulation: Uniformitarianism Revisited
AU: * Rosenbloom, N A
EM: nanr@ucar.edu
AF: National Center for Atmospheric Research, 1850 Table Mesa Dr, Boulder, CO 80307 United States
AU: Harden, J W
EM: jharden@usgs.gov
AF: U.S. Geological Survey, 345 Middlefield Road, ms 962, Menlo Park, CA 94025 United States
AU: Neff, J C
EM: neffjc@colorado.edu
AF: University of Colorado Boulder, Benson Earth Sciences, Campus Box 399 2200 Colorado Ave, Boulder, CO 80309 United States
AU: Schimel, D S
EM: schimel@ucar.edu
AF: National Center for Atmospheric Research, 1850 Table Mesa Dr, Boulder, CO 80307 United States
AB: What is the role of hillslope transport in long-term carbon accumulation in soils? How do parent material, climate, and landform interact to produce the landscapes we observe today and to what extent can we use present day conditions to infer the dominant processes of the past? We use the CREEP [Rosenbloom, N.A. et al., 2001] process-response model to ask these questions, exploring the time-evolution of landscape form, soil distribution, and carbon accumulation in an undisturbed prairie site in western Iowa [Harden, J.W. et al., 2002]. The CREEP model simulates differential transport of soil particles, blanket deposition of atmospheric 10Be with eolian dust, and passive advection of soil carbon and 10Be, enabling the preferential enrichment and burial of rapidly moving soil constituents. By comparing landscape-wide average accumulations of 10Be to borehole observations at three hillslope positions, we conclude that the distribution of clay-adsorbed 10Be cannot be explained by co-transport with clay particles alone. Rather, 10Be appears to behave as a more complex tracer than originally assumed, requiring an explicit, independent parameterization of wet deposition and transport. By comparison, model carbon accumulation strongly reflects patterns of clay redistribution indicating that in situ carbon turnover is faster than redistribution. Observed vertical distributions of soil properties, including 10Be, could only be explained by assuming variations in deposition and erosion rates, specifically periods of accumulation, followed by periods of transport. This effect might not be apparent if only landform shape, geometry, and soil depth were considered and vertical distributions of soil properties were not explicitly simulated. The current landscape reflects a history of strong shifts in erosion and accumulation rates that cannot be simulated using a uniform parameterization of long-term landscape-evolution processes.
DE: 1625 Geomorphology and weathering (1824, 1886)
DE: 1815 Erosion and sedimentation
DE: 1824 Geomorphology (1625)
DE: 1851 Plant ecology
SC: Hydrology [H]
MN: 2003 Fall Meeting