SHELTER-WOOD COMPARTMENT SYSTEM. 



229 



on by all age gradation during one year, the above formula 

 may be written thus : — 



This is the growing calculated for autumn. For spring it is 



G 



IX 



~^, and for the middle of summer (r„ = 



IX r 



The growing stock calculated according to this formula is 

 larger than that calculated from yield tables for short, and 

 smaller for high rotations. The subjoined table shows 

 this. 



h. Sheltcr-trood Coiii/iaiimenf Sijstem. 



The normal growing stock is the same as for the clear 

 cutting system, provided the regeneration cuttings are so 

 arranged, that one-half are made before the year r, and the 

 other half after it. Strictly speaking, this is only correct, if 

 the timber in the regeneration class is removed in annually 

 equal quantities, and if regeneration takes place in the middle 

 of the period. In reality, this does only rarely occur, but the 

 deviations compensate each other in the long run ; anyhow a 

 more accurate determination is practically impossible. 



