SOIL DISTURBANCE BY SKYLINE YARDING VS SKIDDING IN A LOAMY HILL FOREST

Soil disturbance was assessed on harvested units of mature southern pines (Pinus spp. ), where a part of each unit was logged with a cable skyline system and a part with rubber-tired ground skidders. Effects of the two methods of harvesting were studied by aerial and ground surveys. Cable yarding required 2% less acreage in landings than skidding, and yarding corridors occupied 12% less area than skid trails. Physical and chemical analyses of surface soils (upper 15 cm) showed that loam soils with clay subsoils were most severly affected by the displacement of topsoil after both methods of logging. On 8 to 14% of both logged areas, harvesting activities resulted in significant reductions in organic matter, available moisture holding capacity, and available P, Ca, and K. Silt loam soils were severely compacted by cable yarding in the corridors that consistently ran upslope creating the greatest erosion potential. It is concluded that the carefully planned use of skyline cable systems would minimize the area affected by severe soil disturbance and should be considered for future harvesting in this locale.