FOREST .MANAGEMENT. 33 



Charles liefer i*\etl)od 



Bv cutting the actual annual increment, the growing stock is left 

 undisturbed. In order to convert the actual growing stock into a normal 

 growing stock, it is necessary to decrease the annual cut if the normal 

 growing stock is larger than the actual growing stock; and to increase the 

 cut if the normal growing stock is smaller than the actual growing stock. 

 Heyer expresses this idea by the formula: The annual possibility (P) is 

 equal to the sum (5) of the expected average increments diminished by 

 the nth part of the difference existing between the normal growing stock 

 (Ng) and the actual growing stock (Ag). 



Ng-AG 



P = S- 



n 



" u " is the number of years forming the installation period. 



The field work in this method is timestaking; especially so under the 

 selection system or group system when the actual growing stock can be 

 ascertained only by complete valuation surveys. On the other hand, 

 the method prevents any over-cutting or any under-cutting of the forest, 

 and shows clearly how much of the revenue obtained is, in fact, net revenue 

 and not capital withdrawn; or, how much of the revenue is left latent, 

 being used to increase the original growing stock. This method is well 

 adapted for irregular forests. The method requires : 



i. A detailed description of compartments giving the normal and actual 

 volume, and the normal and actual increment for each compartment. 



2. A statement showing the normal growing stock, the actual growing 

 stock, and the total increment for the period of installation. 



3. A statement enumerating the compartments in which the possibility 

 is to be cut. 



No particular stress is put on reaching a normal gradation of age classes. 



Hondesfyagen Aetljod 



Hr.ndeshagen assumes that the ratio existing between the increment 

 and growing stock is constant. With the help of yield tables, he ascertains 

 the ratio existing between normal increment and normal growing stock 



