66 BULLETIN 791, U. S. DEPARTMENT OF AGRICULTURE. 
plants as a result of the animals planting the seed as they graze. 
Accordingly, progressive succession is especially active where the 
deferred-and-rotation grazing system is strictly applied. 
GENERAL SUMMARY. 
1. The carrying capacity of a large portion of the millions of 
acres of western ranges has been materially decreased as a result of 
too early grazing, overstocking, and other faulty management. One 
of the most serious handicaps has been lack of means of recognizing 
overgrazing in its early or incipient stages, which has carried with it 
inability to correct the factor causing the damage before the carry- 
ing capacity of the range was more or less seriously depleted. 
2. In deciding upon the lands especially in need of improvement in 
the past, stockmen and forest officers regulating grazing have relied 
chiefly upon the general abundance and luxuriance of the forage 
supply and upon trie condition of the stock grazed. By these general 
observations, however, it is not possible to recognize overgrazing 
before a large proportion of the plants have been killed. 
3. The most rational and reliable way of recognizing the incipient 
destruction of the forage supply is to note the replacement of one 
type of plant cover by another, a phenomenon which is usually much 
in evidence on lands used for the grazing of live stock. 
4. In tracing the succession of plant life from the consolidated 
rock to a well-disintegrated, fertile soil several fairly distinct cover 
stages are recognized. These stages may be grouped as follows: 
(1) The algae-lichen type, the pioneer stage; (2) the lichen-moss type 
with its sparse stand of annual herbs, the transition stage; (3) the 
ruderal-weed type or cover of annual plants with a scattered stand of 
short-lived perennials, the first- weed stage; (4) perennial herbs, 
chiefly weeds, the second- weed stage; and (5) the long-lived peren- 
nial grasses, known as the subcliinax, or under some conditions, the 
climax type. 
5. In order to observe the principles of succession in the building 
up as well as in the deterioration of the range, special studies were 
initiated on the high summer range of the Wasatch Mountains in 
central Utah. After a careful survey of the vegetation, four major 
consociations were recognized, namely, the wheat-grass, the porcu- 
pine-grass-yellow-brush, the foxg]ove-sweet-sage-yarrow, and the 
ruderal-early-weed. 
the Wheat-grass consociation. 
6. The wheat-grass consociation is the subcliinax or highest forage 
type suceessionally. The turfed wheat-grass cover binds the soil so 
firmly as largely to prevent the invasion and establishment of other 
