FIG. 22-1 Frequenf ground fires 

 prevent the southeastern pme 

 forests from succeeding into a 

 deciduous forest climax (cour- 

 tesy U.S. Forest Service). 



herbs, are intolerant of freezing temperatures over- 

 winter and hence are shed in the North during the 

 autumnal aspect. Consequently there is considerable 

 seasonal change in forest microclimates, to which 

 animal life must respond. The growing season is 

 sufficiently long to permit full development of new 

 foliage and maturation of seed each year, although 

 the size of the seed crop, upon which many animals 

 depend, varies greatly from year to year. 



PLANT ASSOCIATIONS IN 

 NORTH AMERICA 



The principal plant communities are the 

 following (Braun 1950, Shelford MS). 



Lirjodendron-Quercus association: mixed 

 mesophytic forest. Centrally located on unglaciated 

 Appalachian Plateau. Contains a rich mixture of 

 tree species, white basswood and yellow buckeye are 

 best indicators of the association. 



Quercus (Castanea) association: formerly 

 called oak-chestnut forest but chestnut now largely 

 destroyed by blight and its place in canopy taken by 

 oaks and other species, best developed in Appalachian 

 Mountains (Woods and .Shanks 1959). 



Quercus-Carya association: oak-hickory forest. 

 Center of distribution in Ozark and Ouachita Moun- 

 tains but radiating far into the prairie along river 

 valleys and into Gulf and South Atlantic states. 



Fagus-Acer association: beech-maple forest. 

 Mostly northern in distribution ; two principal climax 

 dominants only. 



Acer-Tilia association: maple-basswood forest. 

 Occurs mainly in Wisconsin and Minnesota and 

 southward to northern Missouri. 



Tsuga-P/nus-northern hardwoods ecotone : 

 mixture in southern Canada and in the Appalachian 

 Mountains of beech, sugar maple, and basswood with 

 eastern hemlock, various northern species of pine, and 

 yellow birch. 



Pinus-Pinus associes: southeastern pine forest. 

 Southern species of pines, often mixed with oak. 

 Form extensive subclimax stands in the south At- 

 lantic and Gulf states. Where fire is prevented, this 

 community is succeeded by oak-hickory, beech, or 

 magnolia-oak forest. 



Magnolia-Quercus association: magnolia-oak 

 forest. Found in southern portions of Gulf states and 

 most of Florida. Dominant trees are coriaceous, 

 broad-leaved, and evergreen ; forests often dense, 

 with deep shade, with Spanish moss and other epi- 

 phytes hanging from branches ; grading southward 

 into tropical forest (with royalpalm) in Everglades 

 and Florida Keys. Early sera! stages include fresh- 

 water marshes and cypress swamps, pine flatlands, 

 scrub oak, patches of prairie, coastal dunes, and salt 

 marshes (Davis 1940). 



294 Geographic distribution of communities 



