THE THEORY AND PRACTICE OF WORKING PLANS 13 



Hunger's formula is undoubtedly well adapted for selec- 

 tion forest. 



Fischer * has suggested the following modification of the 

 formula for normal growing stock when applied to reproduction 

 cuttings : 



wi'= (initial gr. stock+final gr. stock) X—^ — — 



2 



X.5. 



The last figure varying according to the crown density. 



For example: A pine forest which contains, on one acre, 

 14,600 board feet at rotation age (i6o years) is cut by shelter- 

 wood method so that 66 per cent of the volume is removed 

 during a twenty-year period of reproduction, whereby the density 

 is reduced to .5. Substituting: 



• wz; = (14,600-1-4818) X — X. 5 

 2 



= i9,4i8XioX.5 



= i94,i8oX.5 



, 20 

 = 97,090 for • — years 

 2 



= 9709 board feet for any one year, per acre. 

 By formula: 



. ^14,600 

 . i6oX^*^^- — • 

 n 160 , , . 



nv = — = = 7300 board feet per acre. 



Strzeleckis proposed f to figure nv = -(V--\--Vr] where 



2\ 2 2 / 



I'- = volume at I rotation age and TV = volume at rotation age. 



* Allgemeine Forst- unci Jagd-Zeitung, ilarch, 1914, pp. 100-102, briefed 

 For. Quart., Vol. XII, No. 2, pp. 279-280. 



t .\llgemeine Forst- und Jagd-Zeitung, 1S84, p. 88, p. 316. 



