44 



By a close position, when each tree cuts off the side light from its 

 neighbors, the formation of branches is prevented, or the branches which 

 were formed, being overshadowed, soon lose their vitality, die, and finallv 

 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 fullv 

 as large as it is capable of producing, but it is distributed over so many in- 

 dividuals 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 num-* 

 ber of trees to permit to grow so as to balance the advantages and disad- 

 vantages 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. 



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 and pines ; on richer soils fewer in- 

 dividuals will produce satisfactory results, when on poorer soils more indi- 

 viduals must be kept on the acre. The question of the proper number of 

 trees to be allowed to grow per acre at different ages is one of the most dif- 

 ficult, on which practitioners differ widely. 



In general, however, the practitioner has recognized the necessity of 

 preserving a dense position for the first twenty to thirty years of the young 

 crop, sacrificing quantitative development to quality and form. The close 

 stand secures the long, branchless, cylindrical trunk, which furnishes the 

 clear saw-logs of greatest value. Then, when the maximum rate of height 

 growth has been attained, a more or less severe thinning is indicated, in or- 

 der to secure quantitative development, and these thinnings are repeated 

 periodically, to give more light as the crowns close up, and also to utilize 

 such of the trees as are falling behind in this wood production. 



As a result of judicious thinnings, the rate at which the remaining 

 crop develops may be doubled and quadrupled, the heavy, more valuable 

 sizes are made in shorter time, and, where the inferior material removed in 

 the thinnings is salable, a much larger total produce is in the end secured 

 from the acre, for many of the trees which were removed and utilized 

 would have died, fallen, and decayed in the natural struggle for existence. 



In German forest management the amount utilized in thinnings 

 amounts to 25 per cent, and more of the final harvest yield. 



