Figure 4-1. Big bluestem (An- 

 dropogon gerardi), one of the 

 chief dominants in the tallgrass 

 prairie, is a most successful grass 

 because of its numerous well- 

 adapted qualities. (U.S.D.A. Soil 

 Conservation Service.) 



When shrubs or trees such as mesquite or juniper grow closely 

 enough together to form a canopy they become dominants in the 

 uppermost layer, while the grasses are usually dominants in the 

 ground layer. 



The synthetic tables in which kinds of species, population 

 density or cover, and frequency are shown furnish an excellent 

 aid in the quantitative determination of dominants (Tables 3-1 

 and 4-1). The constants (species occurring in more than 80 per 

 cent of the stands) with the highest cover or numerical abun- 

 dance may be designated as dominants. Each layer is considered 

 as having its own dominants — a common practice, especially in 

 Scandinavia. ^^^'^2 ^^ example may be given from northern 

 Colorado.'*^' The Stipa-Bouteloua type Stipa comata, with an 

 average cover of about 25 per cent and a constancy of 1 1.0 per 



Sya««Hetic CHanracteristics o£ time Coxnmuxtity • 129 



