Soil erosion following forest operations in the Southern Piedmont of central Alabama

ABSTRACT:

In recent years, nonpoint source pollution (NPS) has been recognized as one of the major threats to the nation's water quality. Clearly, forest operations such as harvesting and site preparation have the potential to have degrading impacts on forest water quality. However, there exists a gap in the understanding of the nature and extent of NPS pollution problems related to forest operations. The study presented here was performed in Lee County, Alabama to investigate the impact of clear-cut harvesting and mechanical site preparation on a 20-year-old loblolly pine (Pinus taeda L.) plantation on sediment and runoff yield. Sediment and runoff yield responses on treated areas were compared to that of undisturbed areas. Impacts were evaluated by monitoring isolated small plots, 2 m (6.6 ft) by 5.5 m (18 ft), over a two-year period following the harvest prescription. Sediment yield from the control treatment was 0.11 t/ha (0.30 ton/acre) over the study period. Sediment yield increases of 0.11 t/ha (0.30 t/ac) and 1.3 t/ha (3.5 t/ac) were observed from clear cut harvest/site prep/plant (H-SP-P) treatment and clear cut harvest /plant (H-P) treatment, respectively. However, erosion losses from the most erosive treatment, clear cut harvest /plant, was still very low at less than 1 t/ha/.yr. Runoff yield results were similar to those observed with sediment yields from treatments in the investigation. Differences in the two treatments were likely due to the differences in surface roughness, which affects infiltration and surface flow velocity.