operations, site preparation, reforestation, and subse- 

 quent culture operations, such as thinning, prescribed 

 burning, pest and fire control, timber harvesting, and 

 the construction and maintenance of roads and other 

 transportation systems associated with these activi- 

 ties. Forests are generally free of accelerated erosion 

 unless they have been disturbed by fire, grazing, 

 timber harvesting, mining, or construction. 



Typical pollutants caused by silvicultural activities 

 include sediment, nutrient, pesticide, thermal, and 

 organic material (which causes oxygen depletion). 

 Sediment is caused primarily by road construction, 

 but other types of construction, such as that of power 

 and pipe Hnes or dams, also contribute to sediment 

 loads on a local basis. Timber harvesting, aside from 

 the associated roads and skid trails, usually does not 

 produce much sediment. The greatest impact of ero- 

 sion from forest and range lands is not always that of 

 water pollution. In some instances, especially where 

 there is severe sheet erosion or where mass failures 

 occur, the loss of soil productivity is of greater 

 consequence. The available data indicate that the 

 percentage of forest and range lands on which this 

 type of erosion occurs is minimal. 



Nutrient enrichment of streams is a natural process 

 that is fairly constant from all forest and range lands. 

 Decomposition of vegetation is the greatest natural 

 source of nutrients, but livestock and wildlife manure 

 also add to the total load. Some nutrients are de- 

 posited directly into streams and lakes in the form of 

 organic matter as a result of needle cast, leaf fall, and 

 the activities of wildlife such as beaver and muskrats. 

 The decomposition of organic matter within the 

 aquatic ecosystem results in oxygen depletion, which, 

 under certain flow conditions, can cause critical water 

 quality degradation. Both the nutrient and organic 

 matter content of streams and lakes can be increased 

 temporarily by management activities. Fertilization 

 of forests and range lands to increased growth can 

 cause a temporary increase in nutrients immediately 

 after application, especially after the first rainfall. 

 Timber harvesting, especially clearcutting, also can 

 cause a temporary increase in both nutrients and 

 organic matter. Figure 7.11 illustrates the relation 

 between selected land uses and nutrient concentration 

 (total phosphorus and nitrogen) in streams. 



Pesticides could become a major source of non- 

 point pollution from forests and range lands. Inci- 

 dents over the past several years have shown that 

 indiscriminate use of pesticides, either in the type, 

 quantity used, or method or timing of application can 

 lead to severe water quality problems. The use of 

 pesticides on forest and range lands is primarily for 

 control of undesirable insects and vegetation. Re- 

 search has shown that pesticides applied in the proper 



amount, at the proper time, and by the proper 

 method are effective in controlling undesirable insects 

 or vegetation, and cause little pollution. '^ Most pol- 

 lution that does occur results from direct application 

 (drift) to bodies of water or from heavy rainfall 

 within a short time of application. In either situation, 

 the source for pollution exists for only a short period, 

 and the pollutant is immediately diluted when it 

 mixes with uncontaminated water. 



Thermal pollution, the warming of stream or lake 

 waters above a given temperature, also can occur 

 from land management activities. Water temperature 

 is affected by direct exposure to the sun's energy 

 through absorption by the materials that make up the 

 streambed. Any activity that opens up more of a 

 stream or lake to the direct radiation of the sun can 

 have an adverse effect on water temperature. This 

 could be caused by road or other construction, 

 timber-harvesting operations, overgrazing by live- 

 stock or wildlife, or fire. Even when temperatures are 

 raised as a result of these activities, there is some 

 question of whether warming of streams should be 

 considered as pollution in all situations. Warming 

 also can occur as a result of sedimentation (shallow 

 water warms more easily than deep water) or in- 

 creased concentration of suspended matter, either 

 organic or inorganic. Although there is some warm- 

 ing as a result of absorption by the suspended par- 

 ticles, the greater effect of pollution is generally that 

 caused by the sediment or decomposition of the 

 organic matter. 



Many other activities that take place on forest, 

 range, and associated lands also cause nonpoint 

 source pollution. Some of these activities, and the 

 kinds of pollution they cause, are: off-road vehicle 

 use-sediment (grazing-sediment, bacteria, nutrients, 

 and organic material); developed or concentrated 

 recreation use-sediment (bacteria and pathogens); oil, 

 gas, and mineral exploration-sediment (oil and chemi- 

 cals). Pollution from these sources is not a problem 

 on a national basis, but, again, it can be critical in 

 local situations. 



A study by the Environmental Protection Agency'* 

 identified agriculture, urban runoff, and individual 

 waste disposal systems (septic tanks, etc.) as nonpoint 



"U.S. Environmental Protection Agency. Silvicultural chemi- 

 cals and protection of water quality. 1977. 



"U.S. Environmental Protection Agency, national water qual- 

 ity inventory, now reflects "best management practices" as the best 

 method of controlling nonpoint source pollution. The concept of 

 best management practices is based on the premise that if land 

 management activities are carried out under the best management 

 practices known, the level of nonpoint pollution will be acceptable. 

 Management decisions incorporating best management practices 

 for grazing, silviculture, mining, and construction will determine to 

 a large extent the success of the control and abatement of nonpoint 

 source pollution from forest and range lands. 



307 



