CHAPTER VII 



RELATIONS BETWEEN PLANTS AND 

 ENVIRONMENT 



The science which studies the relationships among plants, and their 

 relationships with any part or the whole of environment, is called 

 ecology. Literally, ecology means the study of homes. The physio- 

 logic processes of plants, their structure, and their reactions to con- 

 trolled ecologic factors may be and must be studied in the laboratory; 

 but, how the plant functions in, influences, and reacts to its natural 

 environment can be determined only in the field. (Thus, our whole 

 educational system as it stands is poorly adapted to the study of this 

 extremely important science). 



Associations and Communities. In the field the first observation of 

 relationships is likely to be the fact that plants occur in communities 

 or groups. It is rare to find a single plant at any great distance 

 from other plants. Where the soil, moisture and sunlight will support 

 one plant, it will nearly always support more than one. A colony of 

 the same kind of plants exhibits relationships between individuals, 

 between individuals and the environment, and between the group and 

 the environment. There is competition for minerals, water and sun- 

 light. Those individuals which, because of an earlier start or greater 

 inherent vigor, grow taller and secure more sunlight, or establish a 

 larger root system and secure more water and nutrients from the soil, 

 will stunt, deform, and perhaps even starve out others. 



This competition within the colony arises from the similar require- 

 ments of the individuals and the definitely limited supply of one or 

 more of the factors necessary to life. 1 The grower of plants soon 

 learns the importance of proper spacing, if healthy and valuable indi- 

 viduals are to be secured. The forester knows the value of thinning 

 crowded stands of trees in order to promote the growth of the best 

 timber. As far as nature is concerned the tendency is to produce the 

 maximum of vegetation of whatever kinds can establish themselves in 

 a particular environment, but man's demands for useful species 

 requires management. The total photosynthesis going on in an area 

 must be maintained at a maximum, but it should be channelled 

 through the useful species. Even so, man must remember that many 

 species not directly useful are necessary to the maintainence of the 

 environment. 



The more commonly seen communities of plants, which consist 

 of many species, present another competitive situation, that of 



1 Clements, F. D., Plant Succession and Indicators, The H. W. Wilson Com- 

 pany, New York, 1928, pp. 72-73. 



