FOREST SITE PREPARATION EFFECTS ON SOIL AND NUTRIENT LOSSES IN EAST TEXAS

Site preparation practices are frequently utilized in Southern pine ecosystems to facilitate planting and seedling establishment. Soil and nutrient losses were monitored in 12 bordered erosion plots following four site preparation treatments in a clearcut harvested loblolly pine (Pinus taeda L.) forest in east Texas. Three replications of four site preparation treatments were used: (1) chemical herbicide followed by prescribed fire and mechanical tillage, (2) chemical herbicide followed by prescribed fire, (3) chemical herbicide only, and (4) unprepared control. Annual soil loss from the mechanical tillage and prescribed fire treatments (1273 kg ha-1 and 885 kg ha-1, respectively) was significantly greater than annual soil loss from the chemical herbicide and control treatments (240 kg ha-1 and 219 kg ha-1, respectively). During the first post-treatment year, sediment concentration and overland flow increased significantly in the mechanical tillage and prescribed fire treatments with respect to control. Nutrient (N, P, K, Ca, Mg, and S) concentrations and losses in sediment and overland flow temporarily increased after the mechanical tillage and prescribed fire treatments, but not after the chemical herbicide and control treatments. Nutrient concentrations and losses for all site preparation treatments were relatively small and should have little or no effects on water quality and long-term site productivity.