72 BULLETIN 791, U. S. DEPAETMENT OF AGEICULTURE. 



42. The use of established clriveYN^aj'S and bed gToiinds, especially 

 the latter, tends materially to decrease the carrying capacitj^ of th& 

 lands. Owing to the packing of the soil by the animals, these areas 

 revegetate slowly, the colonization usually starting with species of 

 the early-weed stage. 



43. Yearlong protection of driveways and bed grounds, as well 

 as of other sparsely vegetated lands, tends to promote a sexual re- 

 production no more than deferring the grazing until after seed ma- 

 turity. Deferred grazing has all the advantages of yearlong pro- 

 tection and none of the disadvantages, such, for example, as low or 

 negative reproduction from seed and waste of forage during the 

 period required for revegetation. 



44. Judicious grazing tends to maintain a normal cover of vegeta- 

 tion, while on lands where the stand is sparse, there is a tendency 

 toward the promotion of an ujpward succession leading to the ulti- 

 mate establishment of the subclimax species. Progressive succession 

 is particularly active where the deferred and rotation grazing sj^steni 

 is strictly applied. 



COMPARATIVE FORAGE VALUE. 



45. The grazing value of the vegetative covers is essentially de- 

 termined by the stage of the succession. Locally, and indeed gen- 

 erally, the carrying capacity and forage value are the highest where 

 the cover represents a stage in close proximity to the herbaceous 

 climax and lowest in the type most remote from the climax. 



46. The most dry matter per unit of surface is produced in the 

 wheat-grass cover, but the amount is only slightly greater than in the 

 mixed grass-and-weed cover of which porcupine grass and yellow 

 brush are characteristic. By far the least dry matter is found on 

 the ruderal-weed cover, while the amount produced on the second- 

 weed-stage type averages considerably less than on the mixed grass- 

 and-weed type. All classes of stock considered, the porcupine-grass- 

 yellow-brush cover produces more ]oalatable dry matter than any 

 other. For horses and cattle alone, more palatable dry matter is 

 produced on the wheat-grass consociation. Accordingly, virgin stands 

 of wheat grass afford the highest grazing efficiency and will give the 

 biggest returns when cropped by cattle or by cattle and horses; the 

 mixed grass-and-weed type when utilized by cattle, horses, and 

 sheep; and the weed type, if composed either of plants of the first 

 or of the second weed stage, when utilized by sheep alone. Except 

 in practically a pure-weed type or a pure-grass type, the common use 

 of the lands by the various grazing animals is generally justified. 

 As a rule, when the most stable grass type is cropped by cattle and 

 horses alone, it is soon' sufficiently opened up to permit the establish- 

 ment of at least a moderate proportion of weed plants, most of which 



