CLIMAX COMMUNITIES : PRESENT DISTRIBUTION 245 



tion are suggested by the presence of Abies balsamea and Be tula 

 papyrifera in the north but the substitution for them in the south 

 of Abies fraseri and Betula lutea. 



The compensating effect of latitude is apparent in the altitudinal 

 limits of the association, which increase southward. In the north- 

 ern range of red spruce, it may be found anywhere, as is true of 



7. Mixed hardwood forest in Indiana. Large trees are white oaks.— 



U. S. Forest Service. 



fir. Southward, the approximate lower limit of spruce-fir forest on 

 Alt. Katahdin is 500 feet; in the White Mountains, about 2,500 

 feet; in the Adirondack Mountains, 3,000 feet; in the Catskills, 

 3,500 feet; and in the Great Smoky Mountains, almost 5,000 feet. 

 Deciduous Forest Formation.-This formation occupies all of 

 the eastern United States except southern Florida. Its northern 

 transition to conifer forest extends into Canada along a line from 

 northern Minnesota to Maine. On the west, forest gives way to 



