WHERE DID ALL THE TOPSOIL GO? SOIL FORMATION AND EROSION IN CENTRAL VIRGINIA

Historical agriculture in the central Virginia piedmont and foothills of the Blue Ridge Mountains caused widespread soil erosion. In order to measure the depth of this erosion, comparison to intact soils is required. Old-growth forest sanctuaries on the Sweet Briar College campus in Amherst County appear to present such an opportunity. According to the unpublished county soil survey, campus soils are predominantly of the Hayesville series derived from weathered residuum of micaceous gneiss bedrock. Soil coring was performed inside and outside the sanctuaries on Hayesville units from a range of slope and erosion categories. Rather than finding thick topsoil in the sanctuaries, the A horizon is thin and poorly developed everywhere, and the E horizon is only present in one localized area. Because the age of the "old-growth" forest roughly corresponds to the age of the county, these findings imply that the sanctuary areas have also experienced human disturbance and soil erosion. In this region, forest regrowth occurred after abandonment of the land for agricultural purposes and is linked to greatly reduced erosion rates. Forest age inside and outside of the sanctuaries can thus be used to measure rates of recent topsoil formation.