428 



THE INVESTIGATION OF SUCCESSION. 



in the form of charts, though they may serve merely for an annual census of 

 one or more species when this alone is desired. Permanent quadrats may be 

 modified for various purposes, but they fall more or less completely into two 

 groups, viz, permanent quadrats proper and denuded quadrats. The former 

 are designed to reveal and record the changes shown by the different stages 

 or associes of a sere; they make it possible to follow the course from one stage 

 to the next. Denuded quadrats enable the student to reestablish earKer con- 

 ditions in the area by removing the reaction in some degree, and to produce 

 lacking stages at will. It is not only possible to reestablish every usual stage, 

 but also to prepare a larger niunber of areas with minuter reaction differences 

 and thus obtain an analysis of associes possible in no other way. Most 

 important of all exact methods is the combination of permanent and denuded 

 quadrats into pairs, throughout a series of serai communities and zones, as 

 is indicated later. 



Fig. 47. — Quadrat showing seedlings of lodgepole pine in a Vaccinium cover, 

 Long's Peak, CJolorado. •■ 



The permanent quadrat is staked out and charted in the manner abeady 

 described for the chart quadrat. The selection of areas requires greater care, 

 however, if they are to yield the best evidence of development. Like all 

 accvu-ate work, quadrating is slow, and hence the most important task is to 

 secure the maximimi results with the minimum number of quadrats. As a 



