34 the stud y of plant communities * Chapter HI 



If the major interest in a community is an experimental one and 

 the preliminary analysis and description of the vegetation have not 

 previously been made, the experimenter must first learn and re- 

 cord the characteristics of the community with which he intends 

 to work. Again, after experimentation or treatment, whether it be 

 of the community as a whole or of individual species, it often be- 

 comes necessary to evaluate the results in terms of the community 

 as a whole. There must also be a means of comparing the original 

 and the resulting communities at the beginning and at the end of 

 each experiment or treatment. The relationship of the individual 

 species to the community and the responses of the individual spe- 

 cies can best be interpreted when the constitution of the entire 

 community is positively established. 



It is illogical to proceed with explanations when the subject it- 

 self is indefinite or unknown. Therefore, the first objective in 

 ecological work is to learn the composition and structure of the 

 community under consideration. Then, and only then, logically 

 follow a search for causes, experimentation, and interpretations 

 based upon a firm foundation. 



QUANTITATIVE DATA A NECESSITY 



In the early days of ecology, observation and description were 

 considered adequate for recording the characteristics of a com- 

 munity, but few observers see the same thing in the same way, and 

 few writers have the ability to translate exactly into words the 

 things they have seen. Thus, as in other sciences, ecology has be- 

 come more precise as it has developed and, with its concern for 

 greater detail, has demanded accurate measurement and precise 

 records of vegetation. This has led naturally to quantitative meth- 

 ods and terminology, which are becoming more uniform and, 

 therefore, more useful. Their use permits positive statements con- 

 cerning the numbers and sizes of individuals as well as the space 

 they occupy within a stand. With such data in hand, it is possible 

 to make comparisons of species or groups of species within a stand 

 or between stands. Likewise, the data constitute a permanent rec- 

 ord, which can be referred to again if the same stand or similar 

 stands are studied later. Also, as a permanent record, they are sub- 



