816 JOURNAL OF FORESTRY 



cover at high elevations be maintained at the maximum degree of den- 

 sity in order to bind the soil and prevent its blowing about. 



In the study of the relation of erosion and soil depletion to the vege- 

 tative cover, it was ascertained that all the principal salts in the soil 

 useful in the growth and development of plants, except potash, were 

 much more abundant in the non-eroded soil, the greatest difference 

 being in the total nitrogen content. Due to the greater loss of organic 

 matter, the eroded soils were found to have a maximum water-holding 

 capacity of 46.8 per cent, while the non-eroded soil had a capacity of 

 67,2 per cent. The "non-available" water was found to be 15.6 per cent 

 in the eroded soil and 19.3 per cent in the non-eroded soil. There re- 

 mained for the vegetation 16.7 per cent more water in the non-eroded 

 soil than in the eroded soil. 



By growing peas and other plants on both the eroded and non-eroded 

 soils it was found that there was a remarkable contrast in growth on 

 the two soils. The total dry weight in peas produced was as i to 8.3 

 in favor of the non-eroded soil. Native brome-grass and other species 

 behaved in similar manner. The conclusion is drawn that erosion is 

 detrimental to plant growth, chiefly because it brings about the two fol- 

 lowing conditions of soil impoverishment: (a) Lack of adequate soil 

 moisture, due to the lowered water-holding capacity of the soil, and 

 (b) lack of adequate plant nutrients in the soil, due to reduction in the 

 soluble plant foods. 



The bringing back of the original desirable forage plants on eroded 

 soil whence they have disappeared, due to overgrazing, is extremely 

 difficult. Observations on the Manti National Forest, extending over 

 a period of four years, show that the character of the vegetation fol- 

 lowing overgrazing depends upon the degree of erosion and the result- 

 ing soil depletion. Where the fertility of the soil has been seriously 

 impaired, only rapidly growing and early maturing annuals first occupy 

 the soil. In time, through the elimination of overgrazing, soil fertility 

 gradually improves and the longer-lived, deeper-rooted, more valuable 

 forage species gradually reappear. To completely re-establish the more 

 desirable and perennial species, however, such as occupied the soil be- 

 fore it became depleted, requires years, coupled with expert manage- 

 ment. Special emphasis is placed upon the importance of preserving 

 the dark-colored surface soil and in taking the necessary precautions 

 when incipient erosion becomes apparent. 



The maintenance of a maximum cover of vegetation and the con- 

 tinuance of grazing are antagonistic, and unless recognized principles 

 of range management are practiced there is always danger of impairing 

 the ground cover, followed by erosion and soil depletion. 



