78 . THE THEORY AND PRACTICE OF WORKING PLANS 



5. BY VOLUME.— BASED ON GROWING STOCK AND INCREMENT. 

 AUSTRIAN FORMULA (KAMERALTAXE). 



(a) Description of Method. — This, and the other so-called 

 " formula methods " (" Vorrats methoden ''), is characterized by 

 the fact that the allowed annual cut is determined, apart from 

 any plan of management, by mathematical calculation based 

 on a formula. The main factors in this calculation are the 

 growing stock and the increment. The aim in regulating the 

 cut is to have the actual growing stock (F) and the actual 

 increment (i) approach the normal forest characterized by a 

 normal growing stock (nV) and a normal increment {ni). The 

 period of time in which the actual growing stock is to be brought 

 to point of normality is taken as the whole rotation. This 

 is to be accompUshed by heavier cutting if the actual growing 

 stock is greater than the normal growing stock, and lighter 

 cutting if the actual growing stock is less than the normal 

 growing stock. 



The normal growing stock is calculated by the formula — 



2 



where i = the actual mean annual increment.* In even-aged 

 stands it can also be calculated from yield tables by the formula 



7ft 



w(a-f^+c+ . . . — ), where a, b, c . . . m are the values 



2 



* Barrington Moore, in an article on " Methods of Regulating the Cut on 

 National Forests," Proceedings of the Society of American Foresters, Vol. VII, 

 No. I, has suggested that: " If, as is almost ahvajs the case, the real gromng 

 stock {Gr) is made up of only merchantable trees, it will be manifestly unfair to 

 compare vAth this real growing stock a normal gro^^'ing stock, which includes the 

 small as well as the large trees. The result would be too small a surplus or too 

 large a deficit. To obtain a more correct surplus or deficit a normal growing 

 stock which includes only the merchantable trees should be used. This can be 



foimd by substituting for R in the expression a quantit)-, R' equal to the 



2 



difference between the age of the merchantable trees and the rotation. For 



example, if the rotation is 200 years, and trees become merchantable at 60 years 



the growing stock of merchantable trees necessary to leave on the area would be 



/X140. , /X200" 



■ mstead of — — — . 



