Species are present 



I. In less than 20 per cent of the stands 

 II. In 21 to 40 per cent 



III. In 41 to 60 per cent 



IV. In 61 to 80 per cent 

 V. In 81 to 100 per cent 



A fairly large number of species in classes IV and V indicates 

 floristic homogeneity in the community-type;^^ for example, in 

 the type represented in Table 4-1, the distribution is: I, 29; II, 8; 

 III, 2; IV, 3; and V, 9. (All of the species with a constancy of 20 

 were placed in class I because of the small number of stands.) A 

 high degree of constancy indicates that a species has wide 

 ecological amplitude and is therefore capable of growing in 

 various microhabitats, or that the various stands occur in sites that 

 are very similar in environmental conditions so that species of 

 narrow amplitude can grow in all of them. 



Species that occur in 90 per cent or more of the stands in 

 Central Europe, or in over 80 per cent in Scandinavia, are called 

 constant species, and those with high cover values or numerical 

 abundance are usually good competitors and often dominants. 

 These species are important in characterizing and distinguishing 

 community-types, ^°^-'°^ as indicated by the lists of constants in 

 two community-types in the lower foothills of Colorado, shown 

 below: 



SyB%thetic Characteristics o£ tHe CozttxnmBzmity • 125 



