72 BULLETIN 
42. The use of established driveways and bed grounds, especially 
the latter, tends materially to decrease the carrying capacity of the 
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 drive waj T s 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 upward succession leading to the ulti- 
mate establishment of the subclimax species. Progressive succession 
is particularly active where the deferred and rotation grazing system 
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 palatable 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 
