44 Forestry Quarterly 



Growing stock and increment must be determined by some 

 measure common to both, to be determined by the parties con- 

 cerned. Muret advocates the use of basal area for estimating the 

 yield, rather than the estimate of the actual cubic contents since 

 the cubic contents varies in exact proportion with the basal area. 



Calculation of Grozvth (Increment) : Rests on the comparison 

 of two consecutive reconnaissances. This should be found sep- 

 arately for each compartment of the forest. Account must be 

 taken of the number of trees passing from one class to the next 

 above during the period between inventories. This is found 

 by comparison of the number of trees in each class at each recon- 

 naissance with that of the same class at the preceding recon- 

 naissance. The difference in volume between successive inven- 

 tories, for each diameter class, divided by the number of years 

 between the inventories, gives the periodic annual increment for 

 each class. The whole volume divided by the number of years 

 in the period, gives the average rate of growth of the whole forest 

 for the period. 



Regulation of Yield: One cannot establish a sustained annual 

 yield by this method until the beginning of the second period. 

 The more frequently inventories are taken, the more accurately 

 can this yield be determined. 



"The sustained and annual yield will fix and will justify": 1. 

 Whether the cuttings ought to cover all the increment, more than 

 the increment, or less than the increment; 2. How and where the 

 allowed cut ought to be distributed among the different classes, 

 and what proportion of the old, medium, and young trees it should 

 contain. 



Summing Up: After each period, sum up the results obtained 

 from the different divisions, in a table. This will keep an exact 

 account of what has been done and what should be done. 



There are three unknown quantities in its application, which 

 experience should endeavor to settle : 



1. To conserve the material on the ground, we estimate in gen- 

 eral the gross yield at 300 to 350 cubic meters per hectare (4,200 

 to 5,000 cubic feet per acre). We should not go below this, but 

 seek to increase it. 



2. The most favorable distribution among the different classes 

 of the whole, according to M. Gurnaud is 50 per cent, in the old 



