NOTES. 



461 



ner produces the same amount of wood material in weight, no 

 matter what the species. The volumes would then vary in- 

 versely as the specific gravity or weight of the woods, or 



v l : v 2 = - : -, which is also borne out by the results of the 



S l S 2 



German measurements. 



P. 159. Yield Tables. A picture of the progress of a wood- 

 crop is gained from the study of the so-called yield tables, 

 which give the contents of the dominant growth of fully 

 stocked stands in lo-year periods. For each species and dif- 

 ference in sdil and climate this must necessarily vary, hence 

 normal yield tables are classified into five site classes. In re- 

 ality there is rarely such a full stand to be found as the yield 

 tables give ; they represent the attainable maxima, serving as 

 a standard of comparison. 



The following tables refer to first-class sites, and show the 

 difference in production between shade-enduring fir and spruce 

 and the light-needing pine. An approximation to a statement 

 of saw material in board measure can, for the older age classes, 

 be obtained by multiplying cubic contents by 2 to 3. Only 

 the timber wood (over 3-inch) is stated, and the amount of 

 material to be derived in thinnings, which represents from 20 

 to 40 per cent of the final harvest, is omitted. 



YIELD TABLE OF FIR, SITE CLASS I. 



