WHAT FORESTRY IS AND WHAT IT DOES 187 



forest area, the rate of growth of the whole forest for any 

 given year can be determined. 



Forests prevent soil erosion and floods: Forests help 

 to regulate the flow of streams and prevent floods. Most 

 streams are bordered by vast tracts of forest growths. 



Fig. 127. — Eroded Slope in Western North Carolina. 



The rain that falls on these forest areas is absorbed and 

 held by the forest soil, which is permeated with decayed 

 leaves, decayed wood and root fibers. The forest floor is, 

 moreover, covered with a heavy undergro\\i:h and thus 

 behaves hke a sponge, absorbing the water that falls upon 

 it and then permitting it to ooze out gradually to the valleys 

 and rivers laelow. A forest soil will retain one-half of its 



