QUANTIFYING SOIL PRODUCTION RATES FOR THE MADISON SOILS OF GUILFORD COUNTY, NORTH CAROLINA

The rates of soil production play a vital role in landscape evolution and in the interpretation of various geologic and geomorphologic phenomena. We analyzed the various properties of the Madison soils of Guilford County, North Carolina, from data collected with soil pits and soil augers. We completed a soil pit at 4’x3’x4’ located on the nose of a broad ridge; it showed soil horizons distinctly developed between the A horizon and B horizon as well as abundant and well developed tree roots in the O horizon. These soil properties are characteristic of mature undisturbed soil developed in forested terrain, and are assumed to be products of equilibrium for the study here. The appearance of relict features of the metamorphic bedrock such as zones of stained pebbles provided a marker and suggested an identifiable boundary between the B horizon and C horizon. We calculated topographic curvature at a point by determining the elevation of eight neighboring points using a standard gridding method. Curvature was then used with measured soil densities, bedrock densities and the erodibility constant to calculate soil production rates (Heimsath et al., 1997). Field measurements showed soil mantle thickness, and thus soil production, varying inversely with curvature.