SILVICULTURE. i8i 



formed, being overshadowed, soon lose their vital- 

 ity, die, and finally break off, leaving the shaft 

 smooth, and, if this clearing was effected before 

 the branches had reached considerable size, the 

 amount of clear lumber is increased. 



But again, if the trees are kept too close, if too 

 many trees are allowed to grow on the acre, each 

 one having the smallest amount of foliage and 

 - light at its disposal, the amount of wood produced 

 by the acre may be fully as large as it is capable 

 of producing, but it is distributed over so many 

 individuals that each develops at the very slowest 

 rate, and hence does not grow to useful size in the 

 shortest time. 



To secure his object, producing the largest 

 amount per acre of the most useful wood in the 

 shortest time, the forester must know what number 

 of trees to permit to grow, so as to balance the 

 advantages and disadvantages of close and open 

 position. 



This number differs not only according to the 

 species composing his crop, but also according 

 to soil and climatic conditions and to the age of 

 the crop, as we have seen in the preceding 

 chapter. 



Some trees, having considerable capacity of 

 enduring shade, like the beech, sugar maple, or 

 spruce, may require many more individuals to the 

 acre than the more light-needing oaks or pines ; 

 on richer soils fewer individuals will produce 



