Figure 3-2. A conspicuous layer is formed by the flowering 

 dogwood (Comus florida) in the deciduous forest, occurring 

 from Maine to northeastern Mexico; a pronounced spring 

 aspect. May 10, 1957, near Chester, New Jersey. (U.S.D.A. 

 Soil Conservation Service.) 



the stand, are important economically because in the aggregate 

 they form 10 per cent of the total grass cover on conservatively 

 grazed ranges, and as the grassland improves they become more 

 numerous. ^^ These species (characteristic species of Braun- 

 Blanquet) may also be important in delimiting and describing 

 plant communities.^ '^^ss These various examples illustrate the 

 importance of finding and recording all species in a stand, for the 

 absence of some and the presence of others may indicate present 

 conditions and future trends. 



A decline in the number of species from one area to another 

 may indicate increasingly adverse conditions. For example, the 

 number of species in xeric grasslands in Colorado changes greatly 

 with increasing elevation; 160 species were found in the moun- 

 tain front at 5300 ft, 139 in the foothills at 7500 ft, 130 in the 

 upper foothills at 8400 ft, and only 50 in the subalpine zone at 



Analytic CHaracteristics of the ComMnuBiity • 81 



