FNR 89
forestry & natural resources
ENVIRONMENTAL FORESTRY
Criteria For Evaluating Forestry Activities in Relation to Water Quality Management
P. E. Pope, Department of Forestry and Natural Resources
Forestry activities, potential pollutants, and practices to prevent and reduce pollution are interrelated. The interrelationship and flexibility between these factors allow forest managers to successfully integrate water quality goals with other management objectives, and therefore contribute substantially to a water quality management system on the landscape.
Although any one silvicultural activity affects only a portion of a general forest area at any given time, it is usually a part of a cyclical process designated to yield a continuous supply of wood fiber. Certain activities, such as those associated with establishment and removal of the crop, occur only once during the crop rotation. Depending on the tree species and the area of the country, a crop cycle may span 10 to 100 years or more. However, the impact of certain silvicultural activities on the pollution potential may be heavy during forestry operations and may linger until the forest has sufficiently regenerated to restore the water handling capability of the area to preactivity levels. (This recovery period is usually two to four years.) Other activities, such as those associated with protection from fire, disease, and insects, and those associated with crop improvement, may occur several times during the crop rotation. Thus, the period of silvicultural activities on a given forest site can span the length of the crop rotation.
Potential Pollutants from Activities
The most important pollutants which may be generated by silvicultural activities are sediment and debris, chemicals (including those from nutrients and pesticides), and thermal effects. The origin of the pollutants is generally related to more than one of the activities of the total silvicultural operation.
1.	Sediment
An increase in sediment is the most important common form of pollution resulting from silvicultural activities. The additional sediments usually result from accelerated erosion of soils, but may also result from debris and other organic and inorganic waste. Excessive amounts of sediment affect stream ecology by smothering bottom organisms through the formation of “bottom blankets.” They also carry nutrients and pesticides, clog streams and downstream reservoirs, inhibit the reproduction of many important fish species, and alter stream flow and speed. Suspended sediments interfere with photosynthetic processes by reducing light penetration.
2.	Nutrients
Nutrient loss, above the natural level, may occur when fertilizers are carelessly applied during the course of a silvicultural operation. Soluble nutrients may reach surface or ground water through runoff, seepage, and/or percolation. Insoluble forms may be absorbed on soil particles and reach surface water through erosion processes. Nutrients may also reach surface water by direct washoff of slash, debris, and recently applied fertilizer. Excessive nutrients can lead to imbalance in the natural life cycles of water bodies.
3.	Pesticides
Pesticides, when applied during forest management operations, may be insoluble or soluble. Pesticides when applied aerially and in a broadcast manner may directly enter the surface waters. These chemicals then follow approximately the same pattern as nutrients.
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