156 ECONOMICS OF FORESTRY. 



of stand that will secure the largest amount of 

 deposit, compatible with the most useful form. 



In general, the volume accretion of trees in full 

 enjoyment of light experiences a constant increase 

 in rate after the adolescent stage, and continues at 

 such rate for a long time, often into old age. 



Of course different soil and climatic conditions, 

 as well as light conditions, influence the rate of 

 growth, and the growth of different species also 

 varies in amount. Here again the interesting law 

 of the lever may be noted, namely, that on good 

 sites the development is, to be sure, more rapid, but 

 the culmination in the rate is also reached more 

 rapidly, and the decline is more rapid. Similarly 

 as regards species : those that start with a rapid 

 growth usually reach their culmination sooner than 

 the slower ones, and are apt to decline more rap- 

 idly in their rate, so that in the end the slow but 

 persistent growers may outgrow the rapid ones in 

 height, diameter, and volume. 



In the forest, as we have seen, the individual 

 trees experience an influence in their development 

 from the shade of their neighbors, and as a result, 

 a differentiation of trees into size classes, dominant 

 and inferior growth takes place, and finally as a 

 consequenceVthe dying off of the latter, the dimi- 

 nution in numbers, which we have already discussed. 

 Both height and diameter, as well as volume growth, 

 of these various tree classes, together with the dim- 

 inution in numbers, must be studied to determine 



