NATURE OF THE COMMUNITY 



31 



A south-facing bluff forms a habitat that is almost always warm- 

 er and drier than the average for the region, while a north-facing 

 bluff is cooler and wetter. Barren exposures of rock or high, rocky 

 ridges represent one extreme in local habitats, while flood plains 

 of streams, lakes, and lake margins represent the other. Such habi- 



FlG. 10. Aerial view of the forest that extends along the meandering 

 Sauris River far into the grassland of Nebraska —U. S. Forest Service. 



tats are bound to support numerous species that are not character- 

 istic of the general climate and may even differ in their growth 

 forms. These local variations may be extremely restricted in area, 

 scarcely affecting the general physiognomic picture, as would be 

 true of the vegetation around a spring, or on a boulder in the 

 woods; but they may also be so extensive as to be misleading. 

 Cypress or cypress-gum swamps in some sections of the southern 

 states are so large that they might be viewed solely as a product 

 of climate, especially where little drained land is near supporting 

 upland vegetation. Many of the pine forests of New England and 

 the other northern states lie in a climatic region where spruce and 

 fir should eventually predominate. They are so extensively distrib- 

 uted that some ecologists recognize them as the ultimate growth 

 form for the region and as strictly controlled by climate, whereas, 

 their occurrence within the climatic area is closely associated with 

 light, sandv soils. 



