100 THE THEORY AND PRACTICE OF WORKING PLANS 



The growing stock of Class I trees, which there should always 

 be, is therefore 719 XVX 1-025 = 5532. 



Since there are 13,178 Class I trees, a surplus of 13,178 — 

 5532 = 7646 trees exists. 



The cut for the period over which it is desired to distribute 

 the surplus will be: The present Class I trees, plus the total 

 number of trees reaching Class I in the period, minus the 

 growing stock, all divided by the period. 



A modification may be made by calculating the annual cut 

 on the basis of only the upper classes (the first three or four) 

 instead of on all classes. The sum of these classes is then 

 divided by the number of years which the lowest class used 

 will take to become Class I instead of by the rotation. 



(c) Value and Application. — Practically the only place 

 where the single tree method is used is in India. There it is 

 used almost to the exclusion of all other methods. It is par- 

 ticularly well adapted to mixed tropical forests in which only 

 one or two of the many species found is merchantable. 



The disadvantages of the method are its lack of elasticity, 

 its complexity, and liability to error; it also requires as many 

 data as better methods. Hence it should be used only in excep- 

 tional cases.* ' (f^^^ 



12. BY VOLUME.— BASED ON DIAMETER CLASSES. DIAMETER- 

 CLASS METHOD (HUFNAGL). 



(a) Description of Method. — Variation I. For uneven-aged 

 (selection) forests the cut can be determined if all stands or 



trees more than - years old are known and their increment. 



2 



This presupposes the fixation of the rotation age. By means 

 of ring-counts on stumps of average diameter or from other 



* An attempt to modify this method for application in the United States 

 was made by Walter J. Morrill in an article " Method for Regulating the Yield 

 in Selection Forests," For. Quart., Vol. XI, No. i, pp. 21-27. This method, 

 while rather ingenious, is not of great practical importance since it rests on the 

 very dubious basis of average crown spread. 



