EROSION, PLANT GROWTH, AND RE VEGETATION 183 



valuable plant foods. The coarser portions of the soil which 

 are left are invariably low in plant nutrients. 



With a view to determining the cause of the poor plant growth 

 on eroded soils a large number of tj^ical soil types characteristic 

 of the Wasatch Mountains of Utah were examined chemically .^ 



Fig. s8. — RESULTS OF WATER, WIND, AND SHEET EROSION NEAR TIMBERLINE 

 DUE TO OVERGRAZING. 



The protective vegetation has been largely removed and the fertility of the soil so seriously impov- 

 erished by erosion that few species of plants can e.xist. It will require decades to revegetate 

 such lands thoroughly, and then it can be done only by the discontinuance of grazing for several 

 years. 



The soils studied are typical of those found in the spruce-fir 

 type of the summer sheep range, at approximately 10,000 feet 

 elevation. The soils are of limestone origin and were collected 

 at the same elevation and only a few feet apart. They are 

 therefore comparable in all respects, except that on one soil 

 type the plant cover had been destroyed and erosion had oc- 

 curred, and on the other the plant cover was intact and the soil 

 was in a good state of fertility. 



' Sampson, Arthur W., and Weyl, Leon H., "Range Preservation and its Re- 

 lation to Erosion Control on Western Grazing Lands." U. S. Dept. of Agr. BuL 

 675, pp- 18-22, 1918. 



