Topographic Position and Land Cover Effects On Soil Organic Carbon Distribution of Loess-Veneered Hillslopes in the Central United States.

Soil organic carbon (SOC) is important both for its influence on agricultural productivity and for its role in the carbon cycle. The distribution of SOC is highly variable at the field scale both horizontally and vertically; a portion of SOC’s variability can be attributed to slope position and other topographic factors. This study compares surface SOC concentration by slope position at 6 loess-veneered sites in Major Land Resource Areas 115B, 120A and 120B in the central United States. Data was collected as part of the National Cooperative Soil Survey Shawnee Hills Loess Catenas project located on paired sites, one forested and one previously cultivated, in southern Illinois, southern Indiana, and western Kentucky. Bulk density and SOC data were calculated from surface soil cores. The SOC concentration will be compared between slope positions within each site and at like slope positions between sites using Analysis of Variance (ANOVA). These ANOVA tests are expected to indicate the level of variability due to topography when looking within a single site, and the variability due to land use when comparing data between sites. SOC concentration will be modeled for each site and a general model will be created to describe the overall distribution for all sites. The models may be used to predict surface SOC concentration on similar loess-veneered landscapes, both for improvement of soil mapping and for more accurate prediction of soil carbon content.