DETAILS OF THE METHOD 91 



1. Decide on the length of rotation. This has influence on 

 the possible growth and on the number of age classes which 

 should be represented. 



2. Determine the mean annual growth per acre.* 



3. Ascertain the proportion of the area occupied by each 

 age class.* 



4. If each age class occupies its right proportion of the 

 area the annual cut is equal to the mean annual growth. 



5. If the age classes are not represented in the right pro- 

 portion decide what relation the amount cut for the next 

 few years or for the next cutting cycle shall bear to the mean 

 annual growth. 



6. The amount to be cut having been determined select 

 enough trees to give this amount from the older age classes 

 on the basis of their silvicultural condition, considering par- 

 ticularly such points as individual health, rate of growth and 

 seed-bearing value. On the whole the oldest trees would be 

 removed but opportunity is afiforded for taking out poor 

 individuals of younger age, and of leaving certain thrifty 

 trees of older age. 



The age of standing mature trees cannot be secured directly 

 without cutting or boring into them. As this is unpracticable 

 diameter is taken as the best indication of age and the trees 



selection method success in maintaining its typical form of forest is associated 

 so much more intimately with proper regulation than in the case of methods 

 producing evenaged stands, that brief mention is warranted. In fact regulation 

 either on an annual or relatively short period basis is essential to silvicultural 

 success under the selection method. 



* It is recognized that determining for an unevenaged stand, either the 

 mean annual growth per acre, or the proportion of the area occupied by indi- 

 vidual age classes is a mensuration problem as yet without completely satis- 

 factory solution. However, both problems can be answered within Umits of 

 accuracy which should furnish sufficient control for governing the cut. An 

 attempt to elaborate methods of attacking these mensuration problems is 

 considered out of place here. 



