l82 ECONOMICS OF FORESTRY. 



satisfactory results, when on poorer soils more 

 individuals must be kept on the acre. The ques- 

 tion of the proper number of trees to be allowed 

 to grow per acre at different ages is one of the 

 most difficult, on which practitioners differ widely. 

 In general, however, the practitioner has recog- 

 nized 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 

 order 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 mate- 

 rial removed in the thinnings is salable, a much 

 larger total product 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 util- 

 ized in thinnings amounts to 25 per cent and more 

 of the final harvest yield. 



