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Title: ESTIMATING PARTICULATE ORGANIC CARBON FLUX AT VARIABLE LANDSCAPE SCALES

Author
item HUNTINGTON, T - USGS
item Kramer, Larry
item MARION, D - USFS
item BUELL, G - USGS
item FRIES, T - USGS
item Dabney, Seth

Submitted to: Trans American Geophysical Union
Publication Type: Abstract Only
Publication Acceptance Date: 10/4/2001
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Estimating transport and redistribution of particulate organic carbon (POC) in terrestrial ecosystems is an important objective of studies related to carbon cycling and carbon sequestration. It has been estimated that in the United Sates only about 10 percent of eroded materials, and presumably POC, is exported to the oceans. However, little is known about where POC is deposited along flowpaths that include toeslopes, stream and river alluvium and impoundments. The amount of POC buried in depositional environments globally is thought to be a substantial flux in the carbon cycle but the stability of carbon in these environments and the capacity of these sinks are not well understood. In this analysis the WEPP model was used to estimate the flux of POC from eroding hillslopes to depositional toeslopes at the field scale. POC flux was measured in runoff from small agricultural and forested watersheds and compared with modeled fluxes from larger drainage areas in the same river basins. POC fluxes from larger drainage areas were modeled from both landcover and estimated erosion rates derived from spatial data, and sediment concentration, discharge, and carbon concentration of suspended sediment for specific stream sites. Changes in POC flux per unit area as drainage area increased were used to identify depositional or erosional environments. For conventionally tilled soybeans grown on highly erodible loess-derived soils in Mississippi we measured sediment export and used the WEPP model to estimate that about eight percent of eroded sediments were deposited in toeslope positions and the remainder, about 300 kg C per hectare, was transported in runoff into stream channels.