SUCCESSION AS A FACTOR IN RANGE MANAGEMENT 595 



native species of plants were grown in soil subject to more or less 

 serious erosion and leaching and in soil of the same origin and type 

 but not exposed to erosion, and consequently much richer in organic 

 matter and certain soluble salts. In the case of Canadian field peas 

 grown in the eroded soil 841 pounds of water was required for the 

 production of one pound of dry matter, while in the non-eroded soil 

 only 467 pounds of water, or only .555 as much was required. Other 

 species gave similar figures. Corresponding contrasts in the vegetative 

 development of the plants were also observed. 



This experiment, among other highly important economic facts, 

 shows that succession is doubtless retarded on soils subject to erosion 

 and to other conditions tending to deplete the soil. 



Application of Successiona.l Studies 



The practical application of successional studies to the establish- 

 ment and maintenance of a definite vegetative type will be determined 

 chiefly on the basis of the knowledge one has of the successional stages 

 represented by the dififerent species coupled with their growth require- 

 ments. Let us assume, for example, that on badly eroded or denuded 

 range we desire to reestablish the climax species and the weedy 

 annuals of little or no forage value are the primitive invaders, and 

 that these are followed by the establishment of shallow rooted, rapidly 

 growing, and early maturing biennial and perennial plants. As these 

 vegetational cycles progress and enrich the soil with humus, thereby 

 changing the physical structure, total water-holding capacity, and the 

 wilting coefficient of the substratum, they pave the way for the more 

 exacting deep-rooted perennials which predominate in the climax type. 

 If the successional stages of the conspicuous species are known and 

 their increment from year to year determined, one may be in position 

 to declare definitely whether or not the particular method used of 

 harvesting the crop will, within a minimum period of time, promote 

 maximum positive succession. If it is known that certain temporary 

 vegetative cycles must precede the invasion and establishment of the 

 species desired in this instance it would, of course, be extremely unwise 

 to alter the particular management which has been responsible for 

 the development of these cycles. The climax stage of persistent deep- 

 rooted perennials would naturally invade slowly at first but their ap- 

 pearance would be evidence of the fact that the management under 

 operation was conducive to the invasion and establishment of the 

 species desired and, therefore, there should be no change in the man- 



