322 A NATIONAL PLAN FOR AMERICAN FORESTRY 



Service and the Weather Bureau cooperated. Here for 9 years, 

 1910 to 1919, stream flow from two adjacent watersheds was measured 

 under undisturbed conditions ; then the forest on one watershed was 

 cut. As the forest was mostly aspen, sprouts of this species took 

 possession of the area in the following year, so that the only real 

 result of the cutting was the removal of the conifers which previous to 

 the cutting were dominant on about a fourth of the area. Despite the 

 fact that the forest cover was so promptly replaced by sprouts, the 

 total yearly run-off was increased by about 15 percent and the summer 

 run-off by about 10 percent. Flood crests were advanced about 3 

 days and the maximum height of crest averaged 64 percent greater 

 in the cut-over area than in the undisturbed watershed. As previous 

 to logging the height of crest from the cut-over area exceeded the 

 undisturbed area by 6 percent, the net increase amounted to 58 percent. 

 The silt load of the stream after logging increased seven and one 

 half times. 



OVERGRAZING 



FOREST RANGES 



Overgrazing on forest lands of the West was without doubt much 

 more wide-spread 25 to 40 years ago than at present. However, 

 serious depletion of the herbaceous and shrubby vegetation under the 

 trees of the forest or in the openings within the forest the result of 

 past or present overgrazing still prevails on enormous areas of 

 forest land. The worst of it occurs in the semiarid regions. 



If not utilized too closely, the forage produced each year by herbs 

 and shrubs on forested lands is rather well maintained except in the 

 occasional drought year. Investigations of the Forest Service clearly 

 indicate that perennial herbaceous plants, principally grasses, were 

 once the chief forage on most forest ranges, and this is still true except 

 where these plants have been depleted. Studies also show that 

 where trees do not grow in sufficiently dense stand to form a closed 

 canopy, such as the woodland type, and also in openings in the denser 

 forests, these perennial herbaceous plants if still present, are the chief 

 erosion-control agent. 



Overgrazing disturbs the forest cover chiefly in two ways : first, by 

 consuming more of the herbage of the more palatable plants than they 

 can withstand, and, second, by increased trampling. Under such 

 overutilization, the palatable forage plants are grazed closer and closer, 

 and their vigor is sapped. As these plants produce less forage and 

 their stand is thinned, the less valuable plants are grazed more severely 

 until they, too, are thinned. Studies by the Forest Service show that 

 there are many areas now producing not more than 20 to 30 percent 

 of the forage of which they once were capable, and under such con- 

 ditions erosion is usually severe. 



Conditions in central Utah as a result of past abuse illustrate this 

 depletion. Good stands of wheatgrass and bromegrass in the openings 

 of the aspen and subalpine forest types of the higher mountains were 

 once capable of supporting a cow for a month on less than 2 acres. 

 Remnant areas indicate that soils were deep and rich. Overgrazing 

 depleted the open areas until they supported chiefly annual grasses 

 and weeds, of which 10 acres or more are required to furnish a cow 

 feed for a month. With such an inadequate protective cover several 

 inches of topsoil has been eroded away over extensive areas. 



