Effectiveness and implementation costs of overland skid trail closure techniques in the Virginia Piedmont

Abstract

Soil erosion is influenced by factors such as soil properties, slope, ground cover, climatic conditions, and forest management activities, including skid trails. Skid trails typically represent 2% to 10% of a timber harvest's area; therefore, the potential to negatively affect site productivity and water quality as a result of harvesting is of concern. Soil erosion can reduce site nutrient reserves and increase sedimentation of nearby streams. Forestry best management practices (BMPs) are designed to provide effective techniques for maintaining environmental stability. Although BMPs are widely implemented, few data exist regarding the efficacy and costs of different BMP options for skid trail closure. The study objectives were to evaluate erosion control effectiveness and implementation costs of five overland skid trail closure techniques. The closure techniques were (1) waterbar only (Control), (2) waterbar plus seed (Seed), (3) waterbar plus seed and mulch (Mulch), (4) waterbar plus hardwood slash (Hardwood), and (5) waterbar plus pine slash (Pine). Each treatment was installed following harvesting and replicated on four trails to provide twenty experimental erosion plots. Geotextile sediment traps (Dirtbags) were used to filter skid trail sediment. Accumulated sediments were weighed monthly for one year, and erosion rates were determined for each treatment. Two commonly used erosion models, Universal Soil Loss Equation as modified for forests (USLE-Forest) and Water Erosion Prediction Project for Forest Roads (WEPP-Roads), were also applied to each treatment. Sediment collected from traps indicated that the Mulch treatment was the most effective for reducing erosion (3.29 Mg ha⁻¹ y⁻¹ [1.47 tn ac⁻¹ yr⁻¹]), followed by Hardwood (5.08 Mg ha⁻¹ y⁻¹ [2.27 tn ac⁻¹ yr⁻¹]), Pine (5.40 Mg ha⁻¹ y⁻¹ [2.41 tn ac⁻¹ yr⁻¹]), Seed (13.57 Mg ha⁻¹ y⁻¹ [6.06 tn ac⁻¹ yr⁻¹]), and Control (24.24 Mg ha⁻¹ y⁻¹ [10.82 tn ac⁻¹ yr⁻¹]). Overall, WEPP-Roads estimates were more similar to measured erosion than USLE-Forest estimates, but both models generally agreed with actual erosion trends. The Seed treatment was the least expensive beyond waterbars alone, but it was only moderately effective at limiting erosion. Incorporating slash dispersal and compaction onto overland skid trails during harvesting activities may be the best option for reducing BMP costs and long term soil stability on disturbed soils associated with log skidding.