Measuring and modelling soil erosion processes in forests

摘要

A prime forest resource is clean water for downstream beneficial uses. Sediment from forests may impair those beneficial uses. Sedimentation by water erosion is rare unless road activities, timber harvesting, or fire disturb the forest. We have been researching forest soil erosion processes and developing erosion prediction models for over 10 years. This paper presents an overview of some of our findings. Rut formation dominates road erosion processes. Road maintenance practices that reduce rutting also reduce erosion rates. Road ditches can also be a major source of sediment if the ditches are recently disturbed from construction or maintenance. Generally, if roads are properly designed and located at a sufficient distance from nearby streams, then stream sedimentation is minimal. Forest harvesting activities can lead to increased erosion due to the exposure of mineral soil or the alteration of soil properties due to compaction. Fires can lead to major erosion in forests, especially during the first few years after the fire. Spatial variability of the severity of disturbance is common after fire. Fire effects include a reduction in soil hydraulic conductivity and a loss of the protective organic layer on the soil surface. These two impacts can increase erosion rates by several magnitudes. The Water Erosion Prediction Project (WEPP) model can model disturbed forest erosion processes. The WEPP can be a powerful tool to provide quantitative estimates of the amount of sediment entering forest streams for many management activities. Templates for the current WEPP model and user friendly interfaces have been developed to assist field managers to apply this technology to various forest conditions.