CLIMAX COMMUNITIES : PRESENT DISTRIBUTION 259 



high. Although the stands have subclimax characteristics, there is 

 evidence that they may be succeeded by species characteristic of 

 pocosins. 38 These valuable trees have been cut so systematically 

 that they remain only as small sample stands or in relatively inac- 

 cessible places. 145 



Perhaps the most extensive bog and swamp forests still remain- 

 ing in virgin condition are to be found in parts of the Dismal 

 Swamp in Virginia and in the Okefenokee Swamp in Georgia. 



The plant communities of the banks 155 and islands 197 along the 

 coast, as well as a narrow fringe of the coast itself, are distinctive 

 enough to merit more discussion than can be given them here. The 

 effects of salt spray on vegetation were considered earlier, (p. 102.) 

 Live oak (Quercus virginiana) is the most important tree of the 

 forested areas, and the associated shrubs include Myrica cerifera, 

 Ilex vomitoria, Batodendron arboreum, and several others, mostly 

 evergreens. 199 ' 271 Thus, this maritime climax forest is an evergreen 

 variant of the oak-hickory association. 



Rocky Mountain Forest Complex.— Changes of environmental 

 factors with altitude and the resulting zonation of vegetation on 

 mountains have been discussed earlier (see Fig. 66 and related 

 text). The great height of the Rocky Mountains provides condi- 

 tions for a discontinuous alpine zone on the peaks, a subalpine 

 zone, a montane zone, and a zone of woodland forest, which grades 

 into the surrounding desert or grassland. These zones are recog- 

 nizable by their distinctive climax vegetation over an area extend- 

 ing latitudinally from northern Alberta to the southern end of the 

 Sierra Madre of northern Mexico and from the Black Hills of 

 South Dakota on the east to the eastern foothills of the Sierra 

 Nevada and the eastern slopes of the Cascades on the west. 



Climaxes with so great an areal extent would be expected to 

 vary somewhat in different parts of their ranges, especially as to 

 associated species. The zones are not always continuous, nor are 

 they always all present. Near the northern limits of the area, the 

 lower zones run out and the upper zones are found at relatively 

 low altitudes. Southward all zones are, of course, found at succes- 

 sively higher altitudes. Because the prevailing winds are from the 

 west and carry with them oceanic climatic influences, the entire 

 eastern slope of the Rocky Mountain system has different growing 



1 J J o t> 



