22 
BULLETIN 791, U. S. DEPARTMENT OF AGRICTTLTUEE. 
If this is not done, the retrogression of the vegetation to a pure sec- 
ond-weed stage, or, indeed, to the first-weed stage, is inevitable. 
THE PORCUPINE-GRASS-YELLOW-BRUSH CONSOCIATION. 
As a result of the serious overgrazing in the Wasatch Mountains 
prior to the inclusion of the lands in the Wasatch Forest in 1905, the 
wheat-grass consociation was much injured in many localities. Where 
the fertility of the soil was not appreciably impaired after the de- 
struction of the subclimax grass 
cover, the wheat grasses soon re- 
establish themselves; but where ap- 
preciable erosion took place or where 
a considerable proportion of the sol- 
uble soil nutrients was leached out, 
the wheat-grass species failed to re- 
occupy the lands. On the seriously 
impoverished soils, only a sparse 
stand of short-lived plants at first 
gained a foothold : but on areas where 
the fertility and the water-holding 
capacity of the soil were only slightly 
impaired, grasses, notably small 
mountain porcupine grass (Stipa 
minor) (fig. 8). and its ever-present 
associate, yellow brush (Chrysotham- 
nus laneeolatus), predominated. 
Where the soil was more seriously 
depleted, blue grasses, fescues, brome 
grasses, and others were invariably 
associated with porcupine grass and 
yellow brush. 
After the destruction of the wheat- 
grass consociation by overgrazing, a 
large proportion of the entire cover 
was then either of the early or 
late weed stage; but as a result of correcting the destructive 
factor of overstocking, the porcupine-grass-yellow-brush type now 
constitutes the most extensive consociation of relatively high-carry- 
ing capacity in the high mountain region. 
Small mountain porcupine grass and the local congeneric species 
grow as bunch grass, and the intervening space is occupied by other 
grasses and nongrasslike plants. Where the soil has undergone 
only slight change physically and chemically as compared with its 
condition when occupied by the wheat-grass cover, the stand of small 
mountain porcupine grass and yellow brush is full, and the stand 
Sma 1 
Vlo^n-i-ain Porcupir.egrasS. 
($f/pa m/nor-J 
Fig. 8. — The dominant species of the 
poreupine-grass-yellow-brush conso- 
ciation. . 
