Figure 1-14. Competition may be reduced by the associa- 

 tion of unlike species as in this artificial community of 

 smooth bromegrass {Bromus inermis) and alfalfa {Medicago 

 sativa). Competitive capacity of plants is influenced by the 

 intensity of grazing and trampling. July, Lake Geneva, 

 Wisconsin. (U.S.D.A. Soil Conservation Service.) 



fertilizer (kind, time, amount) and the intensity and time of 

 mowing or grazing. In Pennsylvania the late removal of the first 

 crop, nitrogen fertilization, and higher levels of mowing increased 

 the growth of smooth bromegrass and orchardgrass but decreased 

 that of Ladino clover.'^' 



Moderate grazing by sheep for several seasons eliminates many 

 weedy forbs and as a result the less preferred grasses grow better; 

 on the other hand, heavy grazing by cattle gives some weeds 

 better opportunity to grow. In a careful study of the Wasatch 

 Plateau in Utah, Ellison'^ has shown that the kinds of species in 

 stands heavily grazed by sheep are markedly different from com- 

 parable stands that are either not grazed or are grazed by cattle. 

 Competition between legumes and grasses in the seedling stage 

 may be avoided by planting them in alternate drill rows, and this 

 offsets the tendency for grasses to dominate when sowing is done 



Ecological Ckaracteristics of Species &. Populations 



