96 



THE THEORY AND PRACTICE OF WORKING PLANS 



Table of Estimates 



Medium Trees 



Old Trees 



From the table we find the actual proportion of old and 

 medium trees to be: 



Old trees = 1,800,000 M. feet 

 Medium trees = 200,000 ^l. feet 



Total, 2.000,000 ]M. feet 



The normal proportion should be: 



Old trees, 2,000,000X1 = 1,250,000 

 Medium trees, 2, ooo,oooX 8= 750,000 



But the normal growing stock over the whole area, consider- 

 ing half of the area stocked with 30-inch trees, should be 1.120,000 

 M. This should be di\ided between the two groups as follows: 



Old trees, 1,120,000X5= 700,000 M. 

 Medium trees, i,i2o,oooX|= 420,000 M. 



1,120,000 M. 



Hence although there is a surplus of 1,800,000 — 700,000 = 

 1,100,000 M. feet of old trees, there is a deficit of 420,000 — 

 200,000= 220,000 M. in the medium trees. If all the old trees 

 were cut during the first third of the rotation the growing 

 stock would be depleted. Therefore 220,000 M. feet will be 

 taken from the lower diameters of the large trees, chiefly from 

 the more valuable species, and added to the medium trees. 



