1 82 CONTROL OF EROSION ON RANGE AND PASTURE 



posit them at the base of the slope. On elevated plateaus the 

 wind often blows in great gales. From places where the sur- 

 face soil is dry and exposed, such storms transport enormous 

 quantities of soil. 



Vegetative Cover. — Although the extent of surface run-off 

 and erosion are determined by the combined action of a number 

 of factors, the vegetative cover is the most important single 

 controllable factor by means of which erosion may be largely 

 prevented. Man has little or no control over climate and to- 

 pography, and hence the prevention of erosion, especially on 

 pasture lands, must be accomplished chiefly through the im- 

 provement and preservation of the vegetative cover. On 

 most of our western range lands the native plant cover must be 

 relied upon to protect the soil from erosion, because the condi- 

 tions of growth are not favorable to the establishment of cul- 

 tivated plants. 



Obviously, on well-vegetated lands the soil contains a much 

 larger amount of organic matter than on denuded areas. This 

 greatly increases the water-holding capacity of the soil and its 

 power of absorption. Accordingly, on fully vegetated lands 

 practically no erosion occurs except, possibly, during storms of 

 unusual violence, and even then the erosion is seldom serious. 

 On denuded or sparsely vegetated slopes, however, run-off and 

 erosion may occur after relatively light rain storms. Such 

 factors as overgrazing, permitting the animals on the pastures 

 when the soil is wet, fires, and the like, all of which tend to pack 

 the soil or destroy the vegetative cover, increase the damage 

 from erosion (Fig. 58). 



EROSION, PLANT GROWTH, AND REVEGETATION 



" Erosion, plant growth, and revegetation " may sound like 

 a curious, unrelated combination; but, as a matter of fact, they 

 are intimately associated. It is a matter of common obser- 

 vation that the native vegetation commonly found on eroded 

 or leached soils is sparse and of relatively low stature. Water 

 washing over the surface of the land may remove a large portion 

 of the small particles of soil, and with that soil are carried the 



