THE NORMAL GROWING STOCK 



101 



The Normal Growing Stock. Occasionally, 

 for scientific purposes, it is desired to find out what 

 should be the normal growing stock upon an area 

 which is in proper working rotation, or, in other words, 

 what amount of timber should such an area perpetually 

 "carry," supposing that the amount felled annually 

 exactly equalled a year's growth of timber over the 

 whole area. 



This amount (just after a felling) may be calculated 

 from yield tables by the author's formula. Thus for 

 every acre of normal forest (under any particular crop) 

 felled annually as a final crop, if the number of years 

 between each period in the yield table is the same- 

 Let G = the normal growing stock. 



Vi, V 2 , V s , etc., the volume of timber at the 

 1st, 2nd, and 3rd periods, and so on, 

 up to " p " periods, 

 p = the last period at the end of the rotation. 



CIo, CI 3 , CI 4 , etc. = the current annual increment at 



the 2nd, 3rd, and 4th periods, 

 etc., and so on up to "p" 

 periods. 



N = the number of years between 

 each period. 



Then 



+CI,) 



But if the number of years between each period 

 varies 



Let N 2 , N 8 , N 4 = the number of years respectively 

 between the 1st and 2nd periods, the 2nd and 3rd, the 

 3rd and 4th, and so on, up to " p " periods. 



Then 



G = 



+ N 2 x Na^l x CI 2 J + j(N 3 V 2 ) + N 3 x ^1 x CI 3 } + 



The Normal Annual Yield. The normal annual 

 yield in volume of timber which any normally stocked 

 area under any particular crop is capable of yielding is, 

 for every acre of normal forest felled annually, equal 

 to the average annual increment multiplied by the 

 number of years in the rotation. This amount includes 

 the volume of all thinnings besides the one acre of 

 mature timber felled as a final crop. 



Forest Systems. It will be observed that the 

 foregoing tables refer only to crops grown in high 



