248 THE STUDY OF PLANT COMMUNITIES * Chapter X 



palachian and Cumberland plateaus, the numerous species of this 

 climax grow in varying combination. Fagus grandifolia, Aes cuius 

 octandra, Magnolia acuminata, Tilia spp., Liriodendron tidipifera, 

 Acer saccharum, Quercus alba, and Tsuga canadensis are the most 

 abundant trees, but there are twenty or twenty-five other species, 

 any of which may have climax status. The differing sensitivity of 



FlG. 120. Seventy-year-old jack pine with a strong understory of balsam, 

 indicating the trend that succession may take in the Lake States region.— 

 U. S. Forest Service. 



the species to minor variations in environment result in their oc- 

 currence in all kinds of combinations, which may be referred to 

 as association-segregates. 32 The best indicators of the association 

 are large trees of basswood (Tilia heterophylla) or buckeye (Aes- 

 culus octandra). 



The association prevails in the Cumberland and southern Al- 

 legheny mountains and in the adjacent Cumberland and Allegheny 

 plateaus. 33 Away from this center, there is a progressively increas- 

 ing tendency toward restriction to the most favorable habitats. To 

 the south, the association is seldom found except in the moist coves 



