aSSESSING SOIL IMPaCTS RELaTED TO FOREST HaRVEST OPERaTIONS

Three studies conducted in Alabama evaluated impacts associated with a clear cut harvest in three physiographic regions. Machine impacts were assessed via tabulation of soil disturbance classes, measurement of bulk density and soil strength, or a combination of the two. Soil disturbance classes were similar among all locations with untrafficked areas comprising approximately 20 percent of the harvest tract and the remaining as slightly or heavily disturbed. Soil strength response increased with disturbance intensity in surface and subsurface soil layers, while bulk density did not show a consistent pattern by depth with intensity. Post-harvest erosion data underscored the variability of site response while site preparation and subsequent planting contributed to higher erosion rates. Global Positioning System receivers monitored machine movements and provided a basis for disturbance class assessment. Similarly, positional data were used to create Digital Elevation Models to determine runoff interception by silt fences to assess erosion potential.