TORREYA 



Vol. 39 November-December, 1939 No. 6 



Granite Outcrop Vegetation in Alabama 



RoL.\XD M. Harper 



In various parts of the world, particularly in the southeastern 

 United States, there are numerous approximately level areas of 

 bare rock of several kinds, with interesting vegetation in crevices, 

 pockets, etc.. usually quite different from that growing on cliffs 

 and stream-beds of the same sort of rock.^ Flat rock vegetation 

 is usually exposed to the sun and wind most of the day, while cliffs 

 may be shaded most of the time, if they face away from the equator 

 or have trees growing in front of them. And flat rocks may not 

 have as complete protection from fire and grazing animals as 

 cliffs do. 



Although granite is one of the commonest of rocks, flat or 

 gently sloping outcrops of it are less frequent than cliffs and 

 boulders, in the eastern United States at least. But such exposures 

 (including gneiss, which is very similar chemically) are scattered 

 through the Piedmont region from North Carolina" to eastern 

 Alabama, with isolated areas in Arkansas^ and Texas.* They are 



^ For a sketch of several types of flat rock vegetation, with special 

 reference to the cedar glades of Tennessee, see Ecology 7:48-54, pi. 1. 1926. 

 Another type, investigated later, that has some of the characteristics of 

 flat rock vegetation, is described in Torreya 29: 127-130. 1929. 



- For descriptions of granite outcrops in western North Carolina, inter- 

 mediate in character between flat rocks and cliffs, see H. D. House, Tor- 

 reya 10:29-34. February, 1910; Costing & Anderson, Ecology 18:280-292. 

 April, 1937. The two authors last named have since published a very detailed 

 description of granite outcrop vegetation in east-central North Carolina. 

 (Bot. Gaz. 100:750-768, figs. 1-9. June, 1939.) There is no indication of just 

 where or when the photographs were taken (possibly for protection against 

 botanical vandals), but the vegetation is very similar to that here described, 

 even to the weeds. 



"See Ecology 7:54. 1926. 



^ See Eula Whitehouse, Ecology 14:391^05. 1933. This contains among 

 other things a list of over 200 species of plants, arranged alphabetically in 

 each subkingdom, with no indication of relative abundance, and no distinc- 

 tion between natives and weeds. About 15 percent of the flowering plants 

 listed appear to be weeds. 



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