plant succession and range management. 65 
SUMMARY OF THE EFFECT OF GRAZING ON PLANT SUCCESSION 
ON THE RANGE. 
Grazing may cause either progressive or retrogressive succession, 
depending chiefly upon the closeness with which the herbage is 
* grazed annually and the time when it is cropped. If the forage crop 
is grazed closely before seed maturity each year, the general trend 
of the succesion will be retrogressive ; if, on the other hand, the crop 
is maintained in a high state of vigor at all times and then grazed 
after seed maturity every third or fourth year or so, the succession 
will be progressive, or, if there is virtually a full ground cover, a 
maximum density will be maintained. Premature and too close graz- 
ing not only favor retrogressive succession and ultimately the de- 
struction of the vegetative cover, but also tend to impair the fertility 
of the soil through the devastating effect of erosion. The seriousness 
of the depletion of the soil, provided the lands are judiciously man- 
aged, will determine chiefly the time required for thorough revegeta- 
tion. Therefore, the longer retrogressive succession is permitted to 
operate the longer will be the time required for the reestablishment 
of the forage cover. The final outcome of vegetative degeneration 
and erosion is the translocation of the entire soil formation and the 
exposure of the underlying rocks. As a rule, however, only the rich 
surface layer of soil is removed, a condition which favors the im- 
mediate establishment of a cover of the first- weed-stage plants. 
The continued hard use of established live-stock driveways and 
bed grounds favors the destruction of the more stable type of vegeta- 
tion and the establishment of plants of the early and late weed 
stages. These species afford highly reliable indicators of overgraz- 
ing and thus show clearly what lands are being depleted or soon will 
be in an inferior state of productivity provided the disturbing factor 
is not corrected. Obviously, therefore, the use of established drive- 
ways and bed grounds, especially the latter, tends greatly to decrease 
the carrying capacity of the lands. 
Owing to the hard packing of the soil, these much trampled areas 
revegetate slowly. The succession on bed grounds, for instance, is 
similar to that on depleted lands, the revegetation beginning with 
the early- weed stage and progressing through the intermediate covers 
to the subclimax. 
In the way of revegetation, it is evident that yearlong protection 
of bed grounds and other depleted lands from live stock tends to 
hasten vegetative or asexual reproduction no more than when the 
grazing is deferred until after seed maturity. Deferred grazing, on 
the other hand, has the additional distinct advantage over yearlong 
protection of permitting the forage crop to be grazed during the re- 
stocking period, and of procuring a maximum stand of seedling 
112G55°— Bull. 791—19 5 
