COMPUTING VOLUMES IN PERIOD ALLOTMENT 

 By T. S. Woolsey, Jr., M.F. 



New Haven, Conn. 



In Europe it is customary to calculate the volumes to be cut after 

 allotment to periods by carrying the yield to the middle of the period. 

 For example in compartment 1 in the interesting illustration given by 

 Schlich, ^ the present age of the stand is 80. The timber is held over two 

 periods of 20 years each and cut during the third period, or at an average 

 age of 130 years. To compute the volume to be cut in this case it is 

 merely necessary to multiply the acreage of the compartment by the 

 yield table result for 130 years for the same quality of soil. (In practice 

 this is reduced to the actual per cent of stocking.) Quite a few of the 

 profession in the United States have been accustomed to compute the 

 aggregate stand at 120 years (in the case cited) and then add to this 

 figure half the difference between the yield table figure at the beginning 

 and at the end of the period. This involves two distinct steps, so a 

 longer time is consvimed than when figuring simply to the middle of 

 the period. One writer- has introduced the innovation of merely 

 computing the volume to the initial year of the period, thus ignoring the 

 growth. While this method is obviously inaccurate , yet in the case cited 

 no harm was done, because unusually short periods had been chosen 

 (10 years each) and the figures, obviously tentative and approximate, 

 aimed at being conservative. 



In an interesting article, H. H. Chapman, writing on the "Regulation 

 of Yield on National Forests,"* says: 



"Then, depending on its acreage and volume, a second arbitrary 

 period for cutting this age class is assigned to it, and one-half the possible 

 growth or decay during this period of exploitation is added or subtracted. 

 The possible annual cut is found as before by dividing this final total 

 by the length of the period." (The italics are mine.) Since in the 

 method quoted it has been customary to recognize four age classes or 

 groups (with four periods) it is evident that four periods of no uniform 

 length might vary considerably. With a rotation of, say, 120 years, 



1 Schlich 's Manual of Forestry (Fourth Edition), Vol. Ill, p. 387. 

 - Department of Agriculture Bulletin 234, by D. T. Mason, February 12, 1915. 

 Table 19, p. 37. 



5 Proceedings Society of American Foresters, Vol. VIII, p. 225. 



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