|Starr, G - THE OHIO STATE UNIV.|
|Lal, R - THE OHIO STATE UNIV.|
|Kimble, J - USDA-NRCS|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: November 1, 1998
Publication Date: N/A
Technical Abstract: Long-term monitoring is needed for direct assessment of soil organic carbon (SOC), soil, and nutrient loss by water erosion on a watershed scale. However labor and capital requirements prevent such monitoring at many locations representing principal soils and ecoregions. On larger scales, determination of SOC loss by water erosion or gain by deposition is fraught twith uncertainties. Therefore, diagnostic models need to be developed to assess erosional SOC loss from more readily obtained data. The same factors affect transport of SOC and mineral soil fraction, suggesting that given the gain or loss of conservative soil minerals, it may be possible to estimate the SOC flux from the data on erosion and deposition. One possible approach to parameterization is the use of the Revised Universal Soil Loss Equation (RUSLE) to predict soil loss. This multiplied by the percent of SOC in the near surface soil and an enrichment factor give SOC loss. The data obtained from two Ohio watersheds indicate that a power la relationship between soil loss and SOC loss may be more appropriate. When measured SOC loss in individual events over a 13 yr period was plotted against measured soil loss the data are logarithmically linear (R**2 = 0.75) with a slope (or exponent in the power law) slightly less than would be expected for RUSLE type model. The stable aggregate size distribution in runoff on a plot scale may be used to guess the fate of size pools of SOC by comparing size distributions in the runoff plot scale and river watershed scales. Based upon this comparison, at least 75% of material from runoff plots is deposited on the landscape and the most stable carbon pool is lost from watershed soils to aquatic ecosystems and atmospheric carbon dioxide.