226 THE NORMAL GROWING STOCK. 



The amount of the normal growing stock depends on the 

 length of the rotation ; the higher the latter, the greater the 

 former for one and the same area. 



In calculating the normal growing stock, only the principal 

 part of the woods, which gives the final yield, is taken into 

 account, because, as previously explained, the determination 

 of a sustained yield is, in the first place, based upon the final 

 yield only. 



The normal growing stock can be looked at from the 

 volumetric or the financial point of view. 



1. Calculation of the Normal Growing Stock as regards 

 its Vohinie. 



a. Clear Cutting in High Forest. 



It has already been explained on page 141, that, under the 

 system of clear cutting, the normal growing stock consists of a 

 series of age gradations ranging from years old to ?' — 1 years 

 old, with a difference of one year between the ages of every 

 two succeeding age gradations ; this occurs in a temperate 

 climate, in spring, before the annual increment has been 

 laid on. 



(1.) Calculation from Yield Tables. — If a yield table is 

 available for a forest, which gives the produce standing in it 

 from year to year, the normal growing stock is equal to the 

 sum of all the growing stocks given in that table from the 

 year to the year r — 1 ; that sum would represent the normal 

 growing stock of r units of area for spring. 



If the yield table, and this is generally the case, gives the 

 volumes only from period to period, say for every n years, then 

 the approximate amount of the normal growing stock can be 

 calculated (according to Pressler) by assuming, that the 

 volumes rise within each period of n years according to an 

 aritlnnetical series, that is to say, by adding the same number 

 of cubic feet each year. 



