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." 



Munger * has devised a formula for determining normal 

 growing stock in selection forests. Munger 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= h 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 ^ = 5000 board feet, cc = 5o years, 

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

 feet, then 



tXcc . 



nv = -f reserve 



2 



5000X50 , 



= ^ + 200,000 



2 



2t;0,000 , 



=-^2_J — + 200,000 



2 



= 325,000 board feet for the entire 50 acres 

 = 6500 board feet per average acre. 



Using the formula wz;=— and the same premises wz^ 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 gives on p. 20, is for 50 acres since = 6500. 



