SUCCESSION AS A FACTOR IN RANGE MANAGEMENT^ 



By Arthur W. Sampson 



Plant Bcologist, Forest Service 



By succession is meant the establishment of plant species by a series 

 of invasions in a given habitat causing the replacement of one set of 

 plants by another. This alternation in the vegetative personnel is ap- 

 parent when the natural conditions of the habitat have been disturbed 

 either by physical or biotic forces. 



Where the vegetative cover has been interfered with more or less 

 seriously, as is often the case on pasture and range lands, but where 

 subsequently these disturbances have been eliminated or decreased in 

 intensity, there is a tendency through successive invasions, for the 

 vegetation gradually to become more like the original. The suc- 

 cession continues until the equilibrium is finally established between 

 the environment and the vegetation which it supports. This vegeta- 

 tive stage marks the ultimate, climax, or stable type and is quite in 

 harmony with the world around. 



In general the stability of the vegetation cover of a pasture unit 

 and the cropping of the herbage year after year are not particularly 

 harmonious, though this will depend largely upon the way in which 

 the herbage is grazed. If, for instance, the leafage — the laboratory 

 of the plant — is devoured each season at a time when the elaborated 

 food material is needed for the proper development of the vegetation 

 r.nd for seed production, the effect of grazing may be reflected in va- 

 rious ways. Conspicuous among these are: (1) delay in the time at 

 which growth begins in the spring, (2) decreased size and number of 

 leaves, (3) fewer flower stalks coupled with later appearance of the 

 stalks, (4) delayed seed maturity, limited seed production, and lowered 

 viability of the seed crop, and (5) low germination and limited estab- 

 lishment of seedling plants in the following spring. Hence the sta- 

 bility of the type is interfered with and the invasion and succession of 

 transitory species made possible. 



In the management of the range from the standpoint of the main- 

 tenance of the forage crop, it is extremely important to have a re- 

 liable record as to the changes that are taking place in the composi- 

 tion of the vegetation in general, and especially the extent to which 

 the more valuable, forage species are holding their place against grazing. 



Read before the Botanical Society of Washington, D. C, February 6, 1917. 



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