12 THE THEORY AND PRACTICE OF WORKING PLANS 



stock is the best, most pregnant, numerical expression of sus- 

 tained yield management. To attempt an approach to normal 

 stock conditions in some way, must be the aim of the manager 

 for sustained yield." 



Hunger * has devised a formula for determining normal 

 growing stock in selection forests. Hunger conceives of the nor- 

 mal growing stock as consisting of the reserve left after cutting 

 multipHed by the area, plus one-half the growth which take place 

 on the entire forest for the entire cutting cycle. Expressed as 

 a formula: 



nv= [-reserve for the entire forest; 



2 



where i = the current annual increment on the entire forest and 

 cc = the cutting cycle (period between cuts). 



Example : If for 50 acres i = 5000 board feet, cc = 50 years, 

 that is, I of the 200-year rotation, and reserve = 200,000 board 

 feet, then 



iXcc , 



nv = -f- reserve 



2 



5000X50 , 



= — 4- 200,000 



2 



2^0,000 , 



=~^^— H 200,000 



2 



= 325,000 board feet for the entire 50 acres 



= 6500 board feet per average acre. 



Using the formula nv = — and the same premises nv would 



2 



figure out as 10,000 board feet per acre. 



* Proceedings Society of American Foresters, Vol. X, No. i, pp. 18-21. The 



. 325,000 



example which Munger giv^es on p. 20, is for 50 acres since =6500. 



SO 



