THE THEORY AND PRACTICE OF WORKING PLANS 



91 



the majority of American forests, especially to those where, 

 as in virgin forests, the actual growing stock is far in excess 

 of the normal growing stock and a reduction to normal is of 

 prime importance. 



Summary and Comparison of the " Formula Methods " 

 The " formula methods," or, more properly, the " growing 

 stock methods " (" vorratsmethoden "), for there are other 

 methods employing formulae to determine the cut, all aim 

 to have the actual growing stock approach the normal. This is 

 secured by a purely mathematical ratio of increment and growing 

 stock, whereas, oftentimes, the character of the stands and other 

 conditions of management which do not admit of mathematical 

 expression are of more importance. 



In combination with a careful cutting plan (distribution of 

 cut) the Heyer formula serves as a useful determinator in irreg- 

 ular, uneven-aged forests. It is better than the other formulae 

 for the reasons already detailed under (c) " Value and Appli- 

 cation," although the other formulas will serve as a useful 

 check. The superiority of the Heyer formula is still further 

 evident when the results of the examples based on identical 

 premises are compared: 



* See explanation under No. 5: (a) " Description of Method " and {b) " Ex- 

 ample " of Austrian formula. 



