s 
HARPER: THE ‘‘Pocosin” oF PIKE County, ALA. 219 
(In the pine-barrens frequent fires return the potash, etc., quickly 
to the soil, while in calcareous or clayey soils there are usually 
many earthworms, centipedes, snails, bacteria or other soil 
organisms which assist greatly in converting the leaves into 
humus.*) Another successional factor which doubtless tends to 
diminish the availability of mineral nutrients in the soil is the 
denser shade of the climax vegetation; for this lowers the temper- 
ature of the soil-in summer and probably makes the ground- 
water level more constant, besides diminishing evaporation and 
eremacausis. 
Although no chemical analysis of the pocosin soil has been 
made, it is evident from a casual inspection that it consists mostly 
of siliceous sand, and must be rather poor in soluble minerals, 
like the sandy hammocks of Florida. The climax vegetation of the 
more clayey soils in the same region is found on river-banks, bluffs, 
and sides of ravines, where fire is kept away pretty well by the 
topography; and it differs considerably from that of the pocosin. 
The following list, of trees only, is a generalized one for the upland 
climax forests of the whole southern red hill region of Alabama. 
The species are arranged approximately in order of abundance, 
as before. 
Liquidambar Styraciflua Ostrya virginiana 
Pinus Taeda Oxydendron arboreum 
Liriodendron Tulipifera Acer floridanum 
Fagus grandifolia Fraxinus americana 
Quercus alba Tilia heterophylla? 
Cornus florida i 
Magnolia grandiflora Cercis canadensis 
Pinus glabra Halesia diptera 
Hico a Magnolia acuminata 
Magnolia re Quercus rubra 
Tlex opac Symplocos tinctoria 
Nyssa Sacsiths Magnolia pyramidata 
Most of the species in this list are common also to the pocosin, 
but their relative abundance is different, and the proportion of 
€vergreens is considerably less, being probably not over one third 
Or one fourth. LEvergreens naturally differ somewhat among 
themselves in their soil requirements, and it happens that the 
* Mr. Coville’s valuable paper a the formation of eatsncld (Jour. Wash. ‘Acad. 
Sci. 3: 77-80, 1913) should be consulted in this connection. 
