842 



AMERICAN FORESTRY 



character of the surface receiving the rainfall. Dams 

 are inadequate because by the time the water reaches 

 the streams it is too late to control either its velocity or 

 its burden of silt except at enormous expense. But the 

 forest cover controls both factors automatically. From 

 the time the 

 d o w n pouring 

 rain strikes the 

 first or topmost 

 portion of the 

 tree canopy, 

 until the clear 

 water trickles 

 or oozes into 

 the streambeds 

 below, the for- 

 est interposes a 

 com plete suc- 

 cession of nat- 

 ural barriers to 

 floods and silt. 

 The force of 

 the rain on 

 bare soil dis- 

 lodges it and 

 hardens the 

 surface. The 

 drainage from 

 such a surface 

 is rapid and complete, carrying sediment from the very 

 point of impact, and causing the gullying to begin in 

 every direction. Rain falling through a forest canopy 

 drips gently to earth, upon a carpet of waterholding 



A STRIKING EXAMPLE OF ARTIFICIAL TERRACING 



From this point one may gaze far over this unknown land where hill after hill shows artificial terraces 

 painfuily and patiently built on deforested mountains to prevent further erosion. 



litter and humus below which the soil is kept porous by 

 protection from rain, by root penetration, and by the 

 humus itself. The surface litter forms tiny dams in 

 every depression and retards the formation and flow of 

 surface water, replacing it with seepage. Not only is the 



erosion of soil 

 from the sur- 

 face prevented, 

 but the water is 

 s t r a i ned and 

 kept clear. 

 When abnor- 

 mal rain fall 

 swells the 

 streams, their 

 erosive force is 

 kept low by the 

 absence of silt 

 at their sources. 

 Mr. Lin has 

 contributed in- 

 form ation of 

 inestimable sig- 

 nific ance not 

 only in China 

 but throughout 

 the civil ized 

 world, regard- 

 ing the abso- 

 lute necessity of maintaining forests on mountain slopes 

 as the one adequate means of protecting fertile plains 

 and rivers, and preventing destructive floods. But not 

 until China has fought and won the battle for national 



WU TAI SHAN, SHANSI PROVINCE, CHINA 

 Bottom lands buried in waste from deforested mountains. 



