ALLOTMENT DURING A ROTATION. 247 



Making the calculation for the middle of the growing season, 

 summer : 



Summer, G old = ^, 



( & 



r _Ixr 



'"''new Q 



The quantity I is equal to the total increment of all grada- 

 tions laid on in one year, or the increment laid on \>y one age 

 gradation in course of a whole rotation. Hence the following 

 conclusions may be drawn : 



(1) The annual increment of a series of age gradations is 



equal to the volume of the oldest age gradation. 



(2) The total increment laid on during a rotation is equal to 



twice the normal growing stock, calculated for the 

 middle of summer. 



(3) Calculated for the middle of summer, the total increment 



laid on during one rotation is equalty divided between 

 the old and new growing stock. 



(4) The growing stock must increase, if less than the normal 



increment is removed, and vice versa. 



Example : 



Area of forest = 100 acres. 



Rotation =100 years. 



Data those contained in the table at page 190. 



Calculation made with Mean Annual Increment : 



Annual increment of one age gradation = 55*8 cubic feet. 



,, ,, ,, all gradations = 55'8xlOO = 5580 

 Total increment of all gradations during one rotation 



-5580x100 = 558,000 



Increment laid on by old growing stock = - - -- = 279,000 



new 



lew 



What has been said above holds also good, if the current 



