FRENCH FIR MANAGEMENT IN THE VOSGES 545 



Such would be, then, for the forest under consideration, the normal 

 type ; it is toward this type that the cutting must tend to bring the stand. 



According to inventories on 15,000 hectares of Vosges fir stands, 

 Liocourt found a constant ratio of 1.4 between the number of trees of 

 two bordering diameter classes. 



The material is then minimum at the time. If the cycle adopted for 

 the return of the felling is five years, the average material per hectare 



will then be 239 c. m., increased by the growth during — years, or 



during 2^ years ; it will attain then about 265 cubic meters and include 

 399 trees or, in round figures, 400. One can determine if all the fir 

 stands belonging to private owners have this average volume per 

 hectare. 



In the Vosges, on 20,000 hectares of native forests, where this entire 

 stand has been measured (20 cm. and over), the average volume per 

 hectare is, on an overage, 317 cubic meters, and varies from 196 to 390 

 cubic meters. 



3. Yield 



If the stand is normal, one can obtain the yield by applying the 

 method proposed by Burel, formerly conservator at Epinal. This yield 

 comprises trees rendered available each year by their passage to the 

 higher age class. 



The 219 trees of 15 cm. require 12 years to pass wholly into the 20 

 cm. class, and this class must be represented by 123 trees ; one can 

 dispose in 12 years of the difference, namely, 219-123 = 96 trees of 



20 cm., or per year — =8, and so on. Table 3 gives the results with 



the application of the volume and price. 



• Tabi,e 3. — Yield Calculation 



353 -39-04 16.36 10.65 139-84 



To get the rate of return corresponding to a gross revenue of 139.84 



francs (or in round numbers 140 francs), it is necessary to subtract the 



