PLANT SUCCESSIOI^I' AND EANGE MANAGEMEJSTT. 21 



Owing to the small amount of precipitation that penetrates beyond 

 the shallow matlike surface of the turfed wheat-grass type, bunch 

 wheat grasses and other deep-rooted species are seldom, associated 

 with a fully established stand of the sodded wheat-grass cover. The 

 bunch wheat-grass type, on the other hand, supports a considerable 

 variety of weeds and other plants, both of deep and of shallow 

 rooted characteristics. 



Regardless of the growth form of the wheat-grass cover, yellow 

 brush {CJwysothainnus lanceolatus) is the most characteristic fore- 

 runner of other aggressive perennial plants which gain a foothold 

 as the wheat grasses are killed out by overgrazing or other adverse 

 factors. Small mountain porcupine grass is commonly associated 

 with the yellow brush. As the turfed wheat grass is reestablished, 

 yellow brush and porcupine grass are entirely replaced. In the re- 

 vegetation of the bunch wheat-grass cover, both yellow brush and 

 porcupine grass are rather persistent, as the moisture conditions re- 

 main comparatively favorable to the invading species until the 

 original grass cover is fully reestablished. Eventually, however, 

 most of the yellow brush and porcupine grass plants are crowded 

 out. Thus the invasion and conspicuous establishment of yellow 

 brush and porcupine grass on the wheat-grass type generally indicate 

 clearly that one or more unfavorable factors are at play, which, if 

 permitted to continue, may result in the destruction of the wheat- 

 grass type. On the other hand, the waning of the indicator plants, 

 due to competition with the wheat grass, affords reliable evidence of 

 the reestablisliment of the wheat-grass type. 



There is relatively little difference in the number of cattle and 

 horses that the turfed and the bimched wheat-grass areas are capable 

 of supporting in good condition. Sheep, on the other hand, make 

 better returns on typical bunch wheat-grass lands than on the turfed 

 areas because of the greater variety of forage which the bunch-grass 

 type usually supports. In sjDite of this fact, however, no attempt 

 should be made to overgraze either grass cover with the idea of im- 

 proving the lands for the grazing of sheep. To do so will seriously 

 decrease the forage production of the lands for the grazing of cattle 

 and horses. After a few years of full utilization of the wheat-grass 

 consociation by cattle and horses a large variety of plants usually ap- 

 pears. This natural replacement of the palatable grasses by plants 

 successionally lower in the scale of development will improve the 

 lands for the grazing of sheep and thus bring about a condition which 

 will justify cropping by all classes of stock in proper proportions. 

 Where common use of a wheat-grass range is resorted to, after the 

 cover has partly reverted to the weed stage, the cattle grazed should 

 be reduced in number to the point where the remaining vegetation 

 palatable to this class of stock will be safe from further destruction. 



