FORF.STS 



The exact magnitude will be highly 

 variable, depending on soil and cli- 

 mate. The effects of all such treat- 

 ments on nutrient release, like those 

 of clearcutting, are temporary, self- 

 limiting, and not subject to recur- 

 rence on the same area within the 

 foreseeable future. Though these 

 nutrient changes may be conse- 

 quential for vegetation on the treated 

 area, estimates suggest that any in- 

 fluence on water quality must be 

 slight. 



The Effects of Fertilizers and Other 

 Nutrient Sources — In recent years 

 there has been a sharp increase in 

 the number of experiments and op- 

 erational trials using artificial fer- 

 tilizers to increase timber growth and 

 wildlife food supplies, and to develop 

 protective vegetation on disturbed or 

 eroded soils. Large-scale applications 

 of nitrogen on timberlands, notably 

 in the Pacific Northwest, have pro- 

 voked concern that the added fer- 

 tilizer would enter streams and lakes, 

 increasing eutrophication and perhaps 

 reducing quality of urban water sup- 

 plies. 



Several lines of evidence, including 

 lysimeter studies on fertilized areas 

 as well as the "clean-up" of sewage 

 and other waste waters applied to 

 forest soils, demonstrate that forest 

 ecosystems are highly efficient col- 

 lectors and "sinks" for added nutri- 

 ents. The capacity of such sinks ap- 

 pears great due to the large biomass 

 low in nutrient content, wide carbon- 

 nitrogen ratios of forest organic mat- 

 ter, and the high phosphorus-fixing 

 capabilities of most mineral soils; but 

 the details are poorly known. Again, 

 the possibility of increased nutrient 

 content in soil and vegetation result- 

 ing from fertilization has raised the 

 possibility of greater release follow- 

 ing timber harvest. Such questions 

 point to the need for far more precise 

 characterizations of the "compart- 

 ments" and "fluxes" of ecosystem 

 models before these can have any 

 predictive value. 



Present knowledge of the fate of 

 nutrients entering the soil indicates 



that the more serious source of water 

 contamination would be direct entry 

 of the applied fertilizers into streams 

 and lakes. This might occur either 

 through the distribution into such 

 waters during aerial application, or 

 in consequence of surface washing 

 at some periods of the year. The 

 latter chiefly concerns the borders of 

 streams and the associated system 

 of "temporary" streams where over- 

 land flow mass occurs briefly at pe- 

 riods when the underlying soil is 

 saturated. The extent of such channel 

 expansion and its role in transport 

 of dissolved or fine suspended mat- 

 ter has been generally overlooked. 



Thus far, however, the forest land 

 managers involved have been highly 

 sensitive to water-quality considera- 

 tions and have withheld application 

 of nitrogen fertilizers in the vicinity 

 of lakes or streams. In consequence, 

 the tolerable upper limits of rate and 

 distribution are as yet unknown. But 

 several studies of fertilized water- 

 sheds and monitoring of streams 

 from fertilized areas are already un- 

 der way and will warrant continued 

 attention. 



Another important localized source 

 of nutrient enrichment comes about 

 through the high concentrations of 

 recreational users at major camp- 

 grounds, ski developments, and the 

 like. Treatment of the human waste 

 generated at such areas may or may 

 not render the effluent waters "micro- 

 biologically safe," but the nitrogen 

 and often the phosphorus contents 

 usually enter the streams. The result- 

 ing nutrient load is susceptible to 

 reasonably accurate determination, 

 but the effects on the biology of 

 headwater streams and the magnitude 

 of such enrichment in comparison 

 with other sources mentioned above 

 certainly require study. This problem 

 is only marginally a concern of "for- 

 est management," but in the face 

 of steadily increasing recreational de- 

 mands the solutions are likely to be 

 difficult or expensive. Among the 

 options will be prohibition of such 

 use, elaborate treatment plants or 



new technologies of waste 

 or acceptance of altered water qu 

 In any case, both the projection of 

 recreational expansion and hydrolog- 

 tcal data on the streams should be 

 adequate for prediction of conse- 

 quences when such recreational uses 

 are being considered. 



Bacteriological Quality — Increas- 

 ing recreational use is also a major 

 threat to bacteriological quality of 

 water from forested areas. Small 

 numbers of hikers and workers, like 

 small stock and wildlife populations, 

 can use a large area without making 

 much impact. But in forest areas 

 heavily used by campers, hikers, or 

 workers human waste treatment is 

 commonly inadequate, primitive, or 

 nonexistent, posing possible hazards 

 to downstream users of untreated 

 waters from such areas. Routine 

 treatment offsets any such threats in 

 urban distribution systems but the 

 problem of reconciling health, aes- 

 thetics, and recreational use remains. 



Sediment, the Pre-eminent Fac- 

 tor — Concern with the varied as- 

 pects of water quality, though nec- 

 essary, sometimes deflects attention 

 from sediment load, which is the 

 major, most costly, and almost ubiq- 

 uitous cause of impaired quality. Fine 

 suspended matter, mineral or organic, 

 as "silt" or "turbidity," imposes high 

 treatment costs for urban and some 

 industrial uses. It also clogs irri- 

 gation ditches, destroys spawning 

 grounds and bottom vegetation, and 

 reduces recreational and scenic val- 

 ues. Coarse materials fill channels 

 and divert streams in flood, and 

 often destroy the usefulness of 

 flooded lands. 



Sediment movement into streams, 

 together with flow rate and land- 

 treatment effects, have been the main 

 thrust of watershed research. As a 

 result, the sources of fine and coarse 

 sediments in forest watersheds are 

 reasonably well known, as are the 

 general relationships between sedi- 

 ment production on the one hand, and 



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