Part 2 • The Plant Community 



CHAPTER II 

 NATURE OF THE COMMUNITY 



Recognition of a plant community or distinguishing one com- 

 munity from another is probably simpler than recording the char- 

 acteristics by which the community is recognizable. To refer to a 

 stand of pine, a grassy field, or a lowland forest is, in a sense, rec- 

 ognizing communities, and most of us have done this from child- 

 hood. Such communities are the basic vegetational units of the 

 ecologist, and, therefore, their specific and general characters 

 should be stated to insure agreement as to concepts. 



DEFINITION 



A good working definition is as follows: A community is an 

 aggregation of living organisms having mutual relationships among 

 themselves and to their environment. This applies to the specific 

 example which one has in mind or which one is observing— that is, 

 the concrete community or stand. At the same time, it does not 

 exclude the possibility of visualizing an abstract community syn- 

 thesized from several or many concrete examples or stands. Thus 

 a particular stand of pine would be a concrete community and the 

 community in the abstract would include all the stands of that 

 species. 



A stand need not be limited to trees. Any group of plants satis- 

 fying the definition of a community may be so termed— a mat of 

 lichens on a rock, covering only a few square inches, an algal mat 

 on a pond, or a forest of fairly homogeneous composition extend- 

 ing- over a thousand acres or more. 



MUTUAL RELATIONSHIPS AMONG ORGANISMS 



These include all the direct or indirect effects that organisms 

 have upon each other. Foremost among these is competition, 



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