454 COORDINATION OP FOREST SURVEY 



350. Stand Table by Diameters for Poles and Saplings: When 

 Required. When diameter is definitely substituted for age and area, 

 the growth of the forest for a period of from ten to twenty years into 

 the future will include not only the increase on existing merchantable 

 trees, but the volume of all young trees which grow during the period 

 to a size which brings them into the merchantable class (§ 277). 



The number of diameter classes which will become merchantable 

 will be determined by the length of the period and the rate of growth 

 in diameter. At a rate of 1 inch in five years, trees now 4 inches below 

 the minimum diameter will reach the required size in 20 years. 



In order to predict the growth of the stand for this period, the number 

 of trees of each diameter class included in the group which will mature 

 within the period must be recorded during the forest survey. Either 

 all of the trees of these sizes must be calipered or counted, and the 

 average diameter approximated, or these sizes may be calipered on a 

 part of the area, distributed mechanically to obtain an average for the 

 whole. This again indicates the need for correlation of the method 

 to be used in predicting growth with the timber survey, before the latter 

 is undertaken. 



References 



Coordination of Growth Studies, Reconnaissance and Regulation of Yield on National 

 Forests, H. H. Chapman, Proc. Soc. Am. Foresters, Vol. VIII, 1913, p. 317. 



