123 



drainage development the prairie was encroached upon and restricted. 

 The trees farthest from the streams, speaking in general terms, may be 

 looked upon as the pioneer guard of the extending forest. Such trees 

 are oaks and hickories of various kinds, which are hardy and able to 

 live on wet, acid, or very dry soils, as, for example, the shingle oak 

 (Quercus imhricaria) and post oak (Q. michauxii=minor). In the 

 Charleston area all such forest remnants are so closely pastured that 

 they were not studied ; therefore our series is incomplete. The upland 

 forest in the Bates woods (Station IV, a) may be considered some- 

 what representative of a second stage in forest development. This, 

 however, is not a primeval condition, but one which has been modified 

 by man ; for example, the mature trees have been removed. It is, how- 

 ever, clearly an oak-hickory forest. 



A third stage in forest development is found upon the bottom, 

 nearer the river, the most favorable habitat for tree growth in the re- 

 gion, where the red oak (Quercus rubra) and hard maple (Acer 

 saccharum) form a dense, humid shady forest — a climax mesophytic 

 forest. With these changes in the vegetation there have been corre- 

 sponding changes in the physical environment. The relatively open 

 oak-hickory forests are dry, both in the air and in the ground ; they 

 are well lighted ; they are warmer and cooler relatively ; and they have 

 soil which contains less litter and humus. Fallen trees and stumps 

 decay more slowly on account of the dry environment. As the open 

 woods become closed by the development of a dense forest crown, 

 these conditions are changed in important ways : the woods become 

 progressively darker, more stable in temperature, more humid in air 

 and soil; the litter and humus increase; and all wood decays more 

 rapidly both on account of the moisture, fungi, etc., and the activity of 

 animals. The earlier stages in forest development result in the com- 

 bination of glade and grove — islands of open, and islands of trees — ^but 

 with the extension of the forest by its encroachment upon the glades 

 the forest crown becomes complete and continuous, and a climax for- 

 est has become established. These relations show what kind of factors 

 must be considered in striving to group forest habitats in a develop- 

 mental series. 



The forest associations are here considered in the same sequence 

 as that given in the description of the forest stations, and for this 

 reason the discussion will be brief, being mainly intended to give a 

 uniform treatment to all the animal communities studied about 

 Charleston. A more general discussion of the ecological relations of 

 our common forest invertebrates follows. 



