152 ECONOMICS OF FORESTRY. 



under control of man. With the knowledge of the 

 light requirements and with the judicious use of 

 the axe, the forester is enabled to stimulate or 

 suppress one species or another, and to direct in 

 quantitative and qualitative development the prog- 

 ress of his crop, and finally to secure the regen- 

 eration of entire forest growths with species that 

 to him are most useful. 



Not only is the composition largely a result of 

 changes in light conditions, but the amount of pro- 

 duction ceteris paribus is a function of the light, for 

 the amount of foliage which the single tree can 

 exhibit to the influence of light predicates the 

 amount of wood it produces during the season, 

 provided that food supplies are. accessible. 



The whole art of forestry, in its technical as 

 well as in its financial results, is based upon the 

 knowledge and application of the laws of accre- 

 tion. Just as the manner in which composition 

 and numbers arrange themselves is a result of 

 recognizable laws of development, so the growth 

 of the individual tree as well as the growth of the 

 whole stand of trees in quantity and form is sub- 

 ject to laws which can be formulated. The math- 

 ematics of forest growth, developed by forest men- 

 suration,^ reveal not only how, but how much, trees 



1 The measurements to establish the progress of development 

 are based upon the fact that trees grow annually in length at their 

 tips by addition of shoots, and in circumference by the superposi- 

 tion of a layer of wood over those of former years, which in a 



