PLANT SUCCESSION AND RANGE MANAGEMENT. . '31 
FORAGE PRODUCTION. 
Calling forth, as it does, a conspicuous amount of blue grasses, 
some fescues, a scattered stand of wheat grasses, and other less im- 
portant grasses, and at the same time permitting a number of the 
nongrasslike plants to persist, the porcupine-grass-yellow-brush con- 
sociation ranks high as forage, Expressed in terms of dry matter of 
palatable herbage per unit of surface, the porcupine-grass-yellow- 
brush consociation reaches its maximum production where the two 
dominant species are little more than holding their own in competi- 
tion with the grasses higher in the scale of succession development; 
that is, where the highest possible development of the porcupine- 
grass-yellow-brush cover has been reached. Per unit of area, the 
uppermost development of this consociation, with its typically con- 
spicuous admixture of highly palatable blue grasses, fescues, and other 
grasses, interspersed with numerous nongrasslike species, furnishes 
not only more feed but better herbage than any other forage combi- 
nation that may occur in its lower developmental stages. 
While the study has shown that a decrease in the stand of weedy 
species follows the progressive development of the consociation, it is 
seldom necessary to decrease the number of sheep that are grazed on 
the lands. Owing to the character of the feed, cattle rather than 
sheep should be increased in number to consume the additional grass 
forage, but the bulk of the nongrasslike herbage must be consumed 
by sheep. Except on a turfed grass range, a fair proportion of 
weeds, most of which are palatable to sheep but not to cattle and 
horses, is always present. Full utilization season after season of the 
grass herbage by cattle and horses tends to hold in check any striking 
increment in the grass cover, so that appreciable revegetation may be 
effected only where special methods of management are applied. In- 
deed, close utilization of the grass cover from season to season, as 
already indicated, has a tendency to decrease the grass stand and in- 
crease the stand of nongrasslike plants in much the same proportion, 
thus improving the conditions for the grazing of sheep. 
SUMMARY OF THE PQRCUPINE-GRASS-YEJLLOW-BRUSH CONSOCIATION. 
The cover of small mountain porcupine grass and yellow brush, 
next to the wheat-grass consociation, constitutes the highest and most 
stable forage type. Accordingly where conditions become unfavor- 
able to the maintenance of the wheat-grass cover, but not so adverse 
as drastically to change the fertility and available water content of 
the soil, porcupine grass and yellow brush soon gain dominion over 
the soil. Owing to the practical absence of turf-forming species 
within the porcupine-grass-yellow-brush consociation, precipitation 
penetrates deeply into the soil, hence both deep and shallow rooted 
