Fates of eroded soil organic carbon: Mississippi basin case study

Smith, SV Sleezer, RO Renwick, WH Buddemeier, R

ECOLOGICAL APPLICATIONS 15:6 1929-1940

We have developed a mass balance analysis of organic carbon (OC) across the five major river subsystems of the Mississippi (MS) Basin (an area of 3.2 X 10(6) km(2)) This largely agricultural landscape undergoes a bulk soil erosion rate of similar to 480 t center dot km(-2)center dot yr(-1) (similar to 1500 x 10(6) t/yr, across the MS Basin), and a,soil organic carbon (SOC) erosion rate of similar to 7 t center dot km(-2 center dot)yr(-1) (similar to 22 x 10(6) t/yr). Erosion translocates upland SOC to alluvial deposits, water impoundments, and the ocean. Soil erosion is generally considered to be a net source of CO2 release to the atmosphere in global budgets. However, our results indicate that SOC erosion and relocation of soil apparently can reduce the net SOC oxidation rate of the original upland SOC while promoting neu replacement of eroded SOC in upland soils that were eroded. Soil erosion at the MS Basin scale is, therefore, a net CO2 sink rather than a source.

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