LABORATORY AND FIELD WORK 269 



quadrat, two counting the plants and the third serving as recorder. 

 Quadrat paper, ruled into 100 squares, each square representing a 

 10-foot quadrat, is used for the record. A combination of the chart 

 and list quadrat is made. A symbol, usually an initial letter, is used 

 for each species and a list of the species with their symbols is placed 

 on the margin of the quadrat paper. The symbol of each species, 

 with the number of individuals representing it, is placed within the 

 quadrat space in which it occurs. Thus when the entire 100-foot 

 quadrat is finished the record contains a list of all species found, the 

 number of individuals of each species, and the position of each plant 

 within 10 feet of its actual occurrence. From such a study students 

 may readily determine the dominant species, the subdominant 

 species of societies, and other structural characteristics of the com- 

 munity. 



The quadrat method may also be used for determining the fre- 

 quency of occurrence of the various species of a community. This 

 may be done by using a folding meter quadrat, though some workers 

 prefer a smaller size and some prefer a circle instead of a quadrat. 

 This quadrat is placed in the vegetation and the species occurring 

 in it are listed, the process being repeated at more or less regular 

 intervals throughout the community. The result is that lists are 

 obtained for a large number of small quadrats scattered through the 

 community, the number depending upon the size of the community 

 and the character of the vegetation. The next step is to determine 

 in how many quadrats each species occurs. The dominant species 

 may occur in all of them but most of the secondary species will not. 

 The percentage of the total number of quadrats used in which a given 

 species occurs is taken as the frequency index of that species. For 

 example, if the total number of quadrats is 200 and a given species 

 is found to occur in 72 of them, the frequency index of this species 

 is 0.36. 



Suggested Problems 



1. To make a map of the vegetation of a limited area. 



2. To compare a climax association with a serai community as to 

 number of species and number of individual plants. 



3. To discover which species occur most frequently in a given 

 association. 



4. To study the revegetation of a denuded quadrat. 



The Structure and Local Distribution of Plant Communities.— 

 The quadrat method may be used for studying the structure of 



