Soil erosion control in managed forests is undertaken, and best achieved, for two main reasons. The first relates to soil protection for the sustainable productivity of the forest resource. The second relates to the protection of valuable water resources located in forested catchments. The potential impacts of increased soil erosion and the subsequent delivery of this material off-site, include a general reduction in water quality, adverse health effects on aquatic species, and an increase in the delivery of nutrients and sorbed chemicals to watercourses. This article discusses soil erosion control in managed forests from this twofold perspective. It uses a conceptual framework that emphasizes the link between on-site erosion and the subsequent delivery of this material off-site to the stream channel. The importance of adopting erosion control practices that encourage the reduction of surface runoff, and thereby off-site sediment delivery, is emphasized. The role and effectiveness of selected best management practices used in the control of soil loss and sediment delivery in forestry environments is also discussed within this framework.
[...] Soil erosion strategies often aim to influence some of these factors, especially cover and conservation support, which are manipulated more effectively than topographic or climatic variables. Soil loss in many environments is managed, therefore, by controlling the rate of particle detachment through either maximizing surface cover or minimizing surface runoff. Surface cover management involves practices that aim to protect the soil from detachment by raindrops and water. Surface runoff reduction aims to minimize the accumulation of water into concentrated flows to reduce the detachment and transport of sediment in rills. [...]
[...] Key Factors in Soil Erosion Control Much of the understanding of soil loss and the effect of various conservation practices is derived from research in agricultural areas. However, many of the factors remain the major determining influences of water erosion in other environments. One of the most commonly applied soil erosion models, the universal soil loss equation (USLE) incorporates the effect of factors such as soil erodibility slope steepness and length rainfall erosivity surface cover and conservation support practice These factors have been used in the USLE in the following factorial form; A = RKLSCP Only and R have dimensions. [...]
[...] On-Site Soil Erosion Control On-site control of soil erosion is designed to minimize the detachment and subsequent removal of soil from a range of disturbed land surfaces in a managed forest. There is a hierarchy of sediment sources in these environments ranging from the highly disturbed and compacted areas such as roads and tracks, logged hillslopes to the undisturbed streamside riparian areas. The greatest source of sediment in a managed forest is the road and track network, especially those used frequently by vehicles during logging operations. [...]
[...] Off-Site Soil Erosion Control Controlling the generation and delivery of sediment and attached nutrients is an important process in minimizing off-site impacts of forestry operations. The most effective measures of reducing sediment delivery for off-site protection in forestry environments include: 1. Reducing the volume of overland flow Minimizing direct connectivity of sediment sources with the stream network Promoting vegetative filtering. SUMMARY The understanding required to implement effective soil conservation strategies to manage surface erosion now exists. In many countries, harvesting and vegetation clearance is taking place at an alarming rate and the conservation and protection of many forest environments, and the associated water resources, are in jeopardy. [...]
[...] Soil Erosion and Forestry Operations In pristine or undisturbed forests, soil loss due to the erosional effects of water, wind, and gravity is typically low due largely to the protective cover of abundant over- and understory vegetation, and, above all, a well- developed litter layer promoting infiltration of rainwater and the slowing down of any surface runoff that may develop. Soil loss is exacerbated by disturbances associated with tree removal. The opening or removal of forest canopies during harvesting or land clearing results in potentially large areas of bare soil being exposed to the erosional processes of raindrop splash, overland flow, and, under certain conditions wind. [...]
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