ORGAlflSATlOj^ OF SELECTION-WOKKED FORESTS. 185 



The annual outturn of silver fir forests usually varies from 28 

 to 56 cubic feet per acre at high elevations, and from 28 to 98 

 cubic feet where the climate is less rigorous. By comparing the 

 average annual production calculated for the whole forest with 

 the contents of the exploitable tree, the Amdnagiste can test the 

 correctness of his conclusions relative to the yield of the former 

 exploitations, and in any case guard himself against the risk of 

 being mu<!h abov« or below the true figure. Suppose, for instance, 

 that the annual sum of production per acre is about 70 cubic feet, 

 and that the exploitable tree (take it to be a silver fir) measures 2 

 feet in diameter and contains 140 cubic feet on an average ; the yield 

 would thus be half a tree per acre, or, in other words, if the area 

 ef the forest was 509 acres, 250 trees per annum. 



The order and succession of the Selection Fellings are regulated 

 in a very simple manner. Instead of spreading the annual cutting 

 ■over every crop in the forest, the practice has always been, and with 

 good reason, to allow an interval of rest between two consecutive 

 exploitations in any one place. Hence in o^der that these exploita- 

 tions may be reduced to a regular system, it is expedient to fix a 

 periodicity for the Selection Fellings. Thus, for instance, if it is con- 

 sidered advisable to return once in ten years to the same compart- 

 ment, it will be necessary to work through the entire forest in 10 

 years, a. procedure which necessitates the division of the forest into 

 10 portions or coupes. With natural lines, as far as possible, for 

 boundaries, these coupes need not be equal in area. Nevertheleiga 

 any great diflferenee of area is to be deprecated, at the same time 

 ttat the relative extent of the several coupes should be so fixed 

 that their productive capabilities may be appreciably the same. 

 The partition of the forest into such coupes and the determination 

 of the order in which they should be respectively taken up con- 

 stitutes the Working Plan or permanent framework of the Organisa- 

 tion Project. 



Continuing the illustration of the last but one preceding 

 paragraph, suppose the forest to be divided into 10 equal coupes; 

 each coupe would thus contain 50 acres and the annual fellings 

 would remove from it 5 trees per acre every tenth year. If that 

 number was found to be too considerable, if, in other words, 



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