FOREST COMMISSIONERS REPORT. 



109 



Table 9. — Yield per acre of pure paper birch stands of average density. 



QUALITY 1. 



Although the total stem volume is given in Table 9, the low- 

 est measurement taken in the sample trees was at 43/2 feet, and 

 the disregard of butt swelling makes the yield conservative. 

 The yield in cubic feet was reduced to cords by dividing by 96, 

 as previously explained. To reduce the total yield to mer- 

 chantable volume the figures given would have to be reduced 

 in general from 20 per cent to 30 per cent. The annual rate 

 of growth in volume for the whole stand, as shown in Table 9, 

 is less than the rate of growth of individual trees shown in 

 Table 2. This is largely due to the fact that in measuring the 

 individual trees the very smallest were not included, while in 

 measuring the stand even the smallest, suppressed trees were 

 measured whether they were merchantable or not. After 

 twenty years of age the rate of growth in quality i stands is 

 less than that in quality 2, although their actual volume growth 

 continues to be considerably greater. This is due to their 

 quicker growth in early youth and to their greater volume at 

 all ages throughout the life of the stand. 



