THE THEORY AND PRACTICE OF WORKING PLANS 



99 



annual cut as found above is multiplied by half of the felling 

 period. In order to allow for mortality this number is raised 

 by multiplying by 



/Mortality per cent\ 



The growing stock thus found is compared with the actual 

 growing stock to find whether there is a surplus or deficit. The 

 annual cut is allotted accordingly, distributing this surplus 

 or deficit over a certain period according to the proportion of 

 lower classes and reproduction. 



The area check is applied by prescribing the order of the 

 fellings through the different subdivisions of the working unit 

 A table is drawn up showing for each year the subdivision on 

 which the cut is to be located and number of trees to be removed. 



(b) Example. — 



Total Growing Stock 

 Class 



Rotation = 150 years 

 Felling period = 15 years 



From a table showing per cent of each class, reaching Class I, 

 and the per cent of Class I surviving fifteen years, the following 

 calculation is made: Average annual cut 



_ (i3,i78X.95) + (ii,366X.83) + (i9,77oX.66) + (42,577 

 i5o+¥- 

 X.50) + (ii7,59oX .30) + (215,667 X. 10) 



i5o+¥- 

 _ 12,519+9472 + 13,180+21,288+35,277 + 21,567 



^ 113,303 _ 

 157-5 



157-5 

 719 trees per annum. 



