2 BULLETIN 191, TT. S. DEPAETMEITT OF AGEICULTURB. 



observations of the abundance and luxuriance of tlio forage supply 

 and upon the condition of the stock grazed. The depletion of the 

 lands is seldom recognized by these general observations until their 

 carrying capacity has been materially reduced, or until the animals 

 grazed are in poor condition of flesh. So long as the cover is more 

 or less intact, there is little indication that the range is being slowly 

 but certainly depleted ; the depletion is not recognized until the more 

 palatable and important forage species are in low vigor, and th:ir 

 growth and reproduction seriously impaired, or perhaps not until a 

 large proportion of the plants actually have been killed. Until there 

 is insufficient feed to support the animals, they will retain their con- 

 dition of flesh fairly well ; but long before there is insufficient feed to 

 satisfy their appetites a large portion of the vegetation is killed. 

 To reestablish the stand after impoverishment has reached such an 

 advanced stage requires many seasons of most skillful management. 



Enterprising stockmen and those concerned with the administra- 

 tion of grazing know that the live-stock industry has now reached a 

 point where the intensity of the use of the forage crop must be gov- 

 erned by a finer discrimination than mere observation of the density 

 of the plant cover and the condition of the stock. The margin be- 

 tween what clearly constitutes overgrazing and what is clearly under- 

 grazing must be reduced to a minimum if the lands are to be utilized 

 within from 10 to 20 per cent of their maximum carrying capacity 

 and the herbage cropped on the basis of a sustained yield. 



The most rational and reliable way to detect overgrazing is to 

 recognize the replacement of one type of plant cover by another. 

 Certain more or less temporary species almost invariably succeed the 

 more stable weakened or killed plants on lands that are being over- 

 grazed, hence the incoming species are the most reliable indicators 

 of small departures from the normal carrying capacity of the range.^ 

 It is the object of this bulletin to point out what plants are reliable 

 indicators of overgrazing in the various types and how they may be 

 used as guides in revegetation and the maintenance of the forage crop. 



SUCCESSION OR THE DEVELOPMENT OF VEGETATION. 



In studying the laws underlying the occupation of lands by vege- 

 tation from its earliest stages to the development of the highest type 

 of plant life which the habitat is capable of supporting, a somewhat 



1 Shantz, H. L. (Department of Agriculture Bulletin 201, 1911), Kearney, T. H., 

 Bvlggs, L. F., Shantz, H. L., McLane, J. W., and Piemeisel, R. L. (Journal of Agricul- 

 tural Research, 1:365-417, 1914), and others, have shown that the character of the 

 native vegetation affords a reliable index of the conditions favorable or unfavorable to the 

 production of farm crops, and have incidentally established correlations between the native 

 vegetation and the available moisture and the physical and chemical properties of the 

 soil. Relationships between the native vegetation and the carrying capacity of range 

 lands have been developed through the investigations here reported, application of which 

 appears to be of far-reaching importance in the judicious management of the lands. 



