Soil Erosion Potential of Major Timber Harvesting Methods and Harvest Seasons
摘要
Mechanized timber harvesting operations can result in increased soil disturbances, altering sedimentation rates in nearby water bodies and thereby reducing stand productivity. However, appropriate harvesting methods assisted by well-executed forest best management practices (BMPs) can considerably reduce soil erosion. Hence, this study was designed 1) to estimate and compare soil erosion rate using Universal Soil Loss Equation (USLE) for three different harvesting methods (cut-to-length (CTL), tree length (TL), and whole tree (WT)) and two harvesting seasons (winter and summer); 2) evaluate post-harvest percentage of area under various disturbance categories; and 3) to estimate the effectiveness of BMP implementation using audit score. The data were collected from fifteen partial harvest forest sites (completed within 8 months) selected across the state of Maine, USA. The estimated erosion rate was 0.11, 0.12, and 0.14 Mg ha−1 year−1 for CTL, TL, and WT harvest methods, respectively. For winter and summer seasons, erosion rate was 0.09 and 0.11 Mg ha−1 year−1, respectively. There was no significant difference between the estimated erosion rates. The higher erosion rate in WT could be associated with tree dragging, and less even slash distribution on harvest area and skid trails. The post-harvest ground cover and BMP implementation score were the highest for CTL. A strong negative correlation was observed between erosion rate and BMP implementation score (-0.52). The study will assist forest managers to make informed decisions while determining appropriate harvesting methods and BMPs according to stand conditions. This study emphasizes the importance of forestry BMPs and their appropriate implementation in sustainable forest management.