A GENERALIZED YIELD TABLE 389 



make allowances accordingly in predicting yields. The per cent of 

 full stocking increases with age, so that stands which are understocked 

 in youth, in number of trees per acre, often close together later on 

 in life, and have equal final yields with stands which were well stocked 

 from the beginning, as has been shown by Carter to be the case with 

 white pine. The possible application of the table to uneven-aged stands 

 would involve the determination of its average economic age, or gen- 

 eral age-class, and the density of stocking, present and future, of the 

 main crown cover trees. 



It is believed that the making of complete yield tables, such as include 

 a large number of factors (number of trees, average diameter breast- 

 high, average crown width, separate for dominant and subordinate 

 parts of the stand, etc.) and a thorough analysis of these factors, 

 should open up new possibilities of application. In predicting the yield 

 of an understocked stand it would be useful to see to what age in the 

 yield table the number of main-stand trees it has per acre would cor- 

 respond. By subtracting from this age the present average economic 

 age of the stand a useful figure could be secured by which to gauge 

 the time necessary to elapse before the stand would reach the yields 

 and stocking given in the table. This should, if possible, be checked 

 by consideration of the present average diameter and crown area of 

 the stand, and the average diameter and crown area given in the yield 

 table for different numbers of main stand trees per acre when well 

 stocked. 



In conclusion it seems to the writer that the importance of yield 

 tables for well-stocked regular stands has been greatly underestimated, 

 and that the subject has not been given the position of relative im- 

 portance it should have had in comparison with other forest investiga- 

 tions. Yield tables are. in the writer's opinion, a matter of such im- 

 portance that they could well be given first consideration in forest 

 research for an extended period ; for is it not obviously important to 

 forestry' development to secure land to be set aside for growing of 

 timber? And how can classification of lands for timber growing be 

 fully justified if it is not known what it is possible to produce on all 

 dififerent classes of land under forest management and on any par- 

 ticular parcel of it that comes up for consideration ? 



