240 



CHAPTER V. 



THE NORMAL YIELD. 



UNDER the normal yield is understood that which a normal 

 forest can permanently give. The yield may be annual, or 

 intermittent. Instead of determining the yield for each year, 

 or certain intermittent years, it can be ascertained for a num- 

 ber of years, in which case it is called the periodic yield. 



The yield is composed of the final and intermediate returns. 

 The regulation of the yield deals principally with the former, 

 for reasons which have been explained at p. 175. 



The yield of major produce is further sub-divided according 

 to the different classes of wood, such as timber, fagots, root- 

 wood, &c. In order to bring them into the account, all the 

 different classes of produce are reduced to one common 

 standard, that is, " the solid cubic foot." 



The yield can be determined by area and volume, or by its 

 financial value. 



1. The Yield determinedly Area or Volume, 

 a. Clear Cutting in High Forest. 



(1) The Normal Final Yield is equal to the volume which 

 stands on the oldest age gradation. 



A A 



The normal cutting area is c = or = - - , according as to 



r r + s 



whether the cleared area is at once re-stocked or allowed to lie 

 fallow for s years (see p. 213). The volume standing on c 

 must be equal to the volume of the oldest age gradation in a 

 normal series of age gradations, if it is to give the normal yield. 



The periodic normal coupe is = Xn,or = x u. 



r r+s 



