THE STRUCTURAL CHARACTERISTICS OF THE COMMUNITY 27 



vegetation can best be carried out and what characteristics of the com- 

 munity will, under the given conditions, give promising results. 



In the analysis of vegetation few methods have developed for 

 application to other than the higher plants. The following directions 

 have to do with the rooted and clinging communities. The analysis of 

 floating communities (plankton) , a field that is very specialized and as 

 yet but little worked, is relegated to a brief concluding section. 



Kind of Sample Plot. — The analysis of a plant community may be 

 an end in itself. Mostly, however, it is done for the purpose of evaluat- 

 ing the sample sociologically and of establishing its place in the associa- 

 tion. In the latter case the choice of the sample plot is of utmost 

 importance. 



As a general rule, every sample plot, whether large or small, 

 precisely delimited or not, should show the greatest possible uniformity, 

 not only in regard to its floristic composition, which determines the 

 appearance or physiognomy of the community, but also in regard to 

 soil and relief as far as these can be observed. Areas without uniform- 

 ity should be withheld from the beginner. The demand for uniformity 

 in the sample plots leads in itself to distinguishing the communities 

 from one another and to a fragmentation of the plant covering of the 

 earth. Every unit portion that is distinguished must first be studied 

 by itself. The defining of the unit areas of vegetation (which not infre- 

 quently are individual associations) is not always easy, since mixtures 

 are abundant, and between two different uniformly organized pieces of 

 vegetation we very often find narrow or broad transition strips. Here 

 the boundaries should be so chosen as to omit the heterogeneous trans- 

 ition zones. 



Furthermore, an apparently uniform area may consist of compo- 

 nents of two or more different associations such as occur on steep 

 grassland with regular terraces (Seslerieto-Semperviretum, Varietum 

 tatricum, Fig. 10), on stone-covered pasture, or on rock wall with 

 crevices. In this case each component of the uniform mosaic must be 

 studied separately. 



Size of Sample Plots. — A complete record requires the study of the 

 uniform community throughout its entire area. In small communities, 

 like the epiphytic communities on trees or high alpine grassland com- 

 munities, this is simple and obvious, but it is very difficult in the case of 

 extensive forest, shrub, or grassland communities. If the uniform 

 community is too extensive, the investigator must be satisfied with 

 samples of vegetation. If, as only rarely happens in practice, a more or 

 less homogeneous stand extends unchanged over an area too large to 

 inspect, the area may be divided for sociological investigation into as 



