SOUTHEKJSr APPALACHIAN REGION. 81 



the lands have not been cleared nor have forest fires de- 

 stroyed the humus cover from their surface. The rain- 

 drops are battered to pieces and their force broken bv the 

 leaves and twigs of the trees, and when their spray reaches 

 the ferns, the grass, and the flowers below, instead of 

 running away down the surface slope it passes into the 

 spong3' humus, and thence into the soil and the crevices 

 among the rocks below. As much of this supply as is not 

 subsequentlj'- used by the growing plants emerges from 

 this storehouse weeks or months later in numberless 

 springs. (See PI. XXXL) The rain must be extremely 

 abundant or long protracted to produce any excessive 

 increase in the flow of the adjacent brooks. 



The rainfall in this Southern Appalachian region, as 

 shown in Appendix D (p. 14:3), ranges from GO inches for the 

 year in Georgia to 71 inches in North Carolina. Heavy Heavy ramfaii 



, . renders forest 



rainfalls during short periods are common. Even in an cover necessary, 

 arid or semiarid region, where the rainfall for the year 

 may be 10 inches or less, the absence of the forest cover 

 results in a slow but sure removal of the soil from the 

 mountain slopes. Much more in a region of heav}' rain- 

 fall, like that of these southern mountains, when the forest 

 cover has been destroyed, will the soil removal be certainly 

 and rapidly accomplished. 



In stud5dng the streams of the more northern States it and^water^'^s^tof- 

 is seen that the numerous lakes and the deposits of sand forest'^prowems'^ 

 and gravel spread over the hills and valleys of that region 

 b}'' the glaciers serve to store the water and to preserve 

 the uniformity in the flow of the streams, and would ac- 

 complish much in this direction even were the forests in 

 that region entirely removed. In this southern region the 

 preservation of the soil and the streams is. a task which the 

 forests alone must accomplish, and to that end they must 

 be efi'ectively protected. 



The proportion of cleared and forest-covered land in Pioportion of 



^ cleared land in 



each of the great river drainage basins of the reslon is Appalachian re- 



° » & gion increa.sing. 



given on page 69, and as will be seen there, this proportion, 

 though generally small, varies considerably in the difl'erent 

 basins. Taking the region as a whole, at the present time 

 about 24 per cent of the area has been cleared. (See PI. 

 XII.) This proportion is an ever-increasing one — increas- 

 ing the more swiftly for the reason that new fields are 

 constantly being cleared and the abandoned fields are being- 

 eroded so rapidly that thev are seldom reforested. (See 

 PI. XXI.) 



