CHAPTER III 



THE STRUCTURAL CHARACTERISTICS OF THE COMMUNITY 



The analysis of plant communities may follow the purely practical 

 lines of forestry and agriculture or the more theoretical lines of plant 

 sociology. For the phytosociologist, the first task is to carve out and 

 delimit the association, in order to lay the most indispensable founda- 

 tion for synecological, synchorological, and syngenetical investigations. 

 Investigations of the laws of the internal structure of plant communities 

 as well as of purely syngenetical matters comprise a narrower field. 



Problems of the structure of communities, as presented by agricul- 

 ture and forestry, form in themselves a very comprehensive complex. 

 These can be considered here only in so far as they are related to the 

 structural studies of general plant sociology. 



Analytic Characters. — Immediately available for phytosociologic 

 analysis, and accessible in every sample of vegetation, in every stand, 

 are the following characteristics of the community, based upon the 

 species present: 



a. Quantitative characters: 



Number of individuals (abundance) and density; 



Cover, space, and weight (Dominanz, Deckungsgrad)s 



Gregariousness (Soziabilitat) and distribution^ 



Frequency. 

 bi QuaUtative characters: 



Layering (stratification)j 



Vitality, vigor (Gedeihen):. 



Periodicity. 



The apparent simpUcity of the analysis of the concept of vegetation 

 is directly in contrast with the difficulty of making any universal rules. 

 Sometimes it is entirely impossible to submit different vegetation types 

 to similar methods of treatment. All too often the attempts to com- 

 bine the most exact counts and measurements of sample communities 

 (stands) into an abstract unit (a plant association) results in nothing 

 but vague averages. "Measure what can be measured, and count what 

 can be counted, but always be conscious that the figures obtained are 

 purely relative." Not infrequently mere estimation gives better 

 results than counting and measuring. In each case, the judgment of 

 the investigator must decide how the minute analysis of a given piece of 



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