66 BULLETlJSr I9i, U. B. DEPAllTMfciVT OF AGRIC!OL.TJJIiB. 



plants as a result of the animals planting the seed as they graze; 

 Accordingly, progressive succession is especially active where the 

 deferred-ancl-rotation grazing system is strictly ax^piied. 



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 

 OA'ergrazing 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 tlie 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 algse-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 subclimax, 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 foxglove-sweet-sage-yarrow, and the 

 ruderal-early-weed. 



THE WHEAT-GRASS CONSOCIATION. 



6. The wheat-grass consociation is the subclimax or highest forage 

 type successionally. The turfed wheat-grass cover binds the soil so 

 firmly as largely to prevent the invasion and (^tabiishment of other 



