Effects of Topographic Features on Postfire Exposed Mineral Soil in Small Watersheds
Exposed mineral soil is an immediate result of forest fires with direct relevance on surface runoff and soil erosion. The goal of this study was to determine which topographic features influence the distribution of exposed mineral soil following wildfire in forested watersheds. In a field investigation 2 months after a simulated wildfire, ground cover was measured and a number of topographic variables, including slope, aspect, distance to streams, solar radiation, elevation, curvature, and profile curvature, were used to determine their relationships to postfire exposed mineral soil. The spatial distribution of fire effects along hill slopes was assessed using geographic information system (GIS), and a regressional relationship was derived to estimate postfire exposed mineral soil from key topographic variables, namely, aspect, solar radiation, and profile curvature. Solar radiation, aspect, and profile curvature were significantly correlated with the amount of soil exposed after the fire; however, aspect and profile curvature were the leading variables in the predictive regression model. Convex-shaped profile curvatures on south-facing slopes had higher values of exposed mineral soil than concave surfaces on north-facing slopes. These results can help land managers with decisions on prioritizing areas in need of pre- or postfire treatment.