(2) Quantitative 



(a) Population density (number of individuals, abund- 



ance) 



(b) Cover (area occupied) 



(c) Height of plants 



(d) Weight of plants 



(e) Volume occupied by plants 

 (/) Frequency 



QUALITATIVE CHARACTERISTICS 



Kinds of Species Occurring in the Community (Floristic Composition) 



A complete list of species is the most essential characteristic of 

 a stand, and the making of such a list is the first step in its study. 

 In practice it is impossible to name all the organisms in a bio- 

 cenose, so botanists usually name only the vascular plants, but it 

 is essential to include the cryptophytes, especially lichens and 

 mosses, in many communities, particularly in arctic and alpine re- 

 gions. In order to secure a complete list, inspection and collecting 

 throughout the growing season are required so that all species 

 appearing in different seasons will be included. The plants need 

 to be correctly named, which often requires the aid of a compe- 

 tent, systematic botanist, and herbarium specimens prepared for 

 future reference and as vouchers. In areas where little ecological 

 work has been done, or where time does not permit detailed 

 study, lists accompanied by accurate descriptions of the whole 

 area may be of more value than detailed records in only one or a 

 few localities. 



Floristic lists are valuable for characterization because each 

 species has its own range of ecological amplitude (Figure 3-1). 

 Each one has its particular relationships to the environment and 

 to other species, so the total number of species, as well as the 

 average number per sample area in each stand, tell much about 

 the conditions of the habitat. For example, 36 species were pres- 

 ent in a certain number of nongrazed sample areas in virgin tall- 

 grass prairie in central Oklahoma, while 64 species were found 

 in the same number of sample areas in the grazed part, indicat- 



78 • Tke Commimnity 



