Edge Effects and Spatial Variability in Coastal Plain Ultisols

Spatial variability of soil types and surface horizon thickness were investigated along a 0.2 km transect near an upland valley side slope in the North Carolina Coastal Plain. Previous studies have shown a variable but systematic pattern of soil properties and surface thickness near such "dry edges." The edge effect model successfully predicts the highly variable pattern of soil cover found at the study site, and explains the generally thick (mean ~1 m) surface horizon thickness on the upland portion of the site. It does not explain the 10-fold variation in A and E-horizon thickness (15 to 152 cm) over less than 200 m, the irregular spatial pattern, and the lack of any trend with respect to distance from the dry edge. The broad-scale patterns governed by drainage and topographic factors have superimposed short-range variability, probably associated with biological factors such as tree throw and faunalturbation.