322 Forestry Quarterly. 



the total yield in cubic feet, as related to age, as the criterion 

 of quality.* Another method is to use heights instead of volumes. 

 This method is based on the experience that the height of an 

 even-aged stand is a reliable index of the quality of site and it 

 has been proved that the classification of sample plots by this 

 method and by that of total volume leads to practically the same 

 results. 



Since Lodgepole pine in this region occurs in remarkably pure 

 and nearly even-aged stands of fairly uniform density, it was 

 safe and a reasonable assumption that, in determining the site 

 quality of stands' in which the measured trees grew, the D. B. H. 

 in inches of the individual tree could be substituted for the aver- 

 age age of the stand ; the total height of the individual tree could 

 be substituted for the average height of the stand. This allows 

 the site qualities to be determined by the use of curves plotted on 

 D. B. H. in inches and the total height of the tree in feet in the 

 following manner : 



All measurements were tabulated by inch diameter classes' and 

 two- foot height classes in a semi-final table, to determine the num- 

 ber of trees of each class. 



The diameters were then plotted as abscissae on a rectangular 

 system of co-ordinates and the height in feet as' ordinates. Be- 

 side each point plotted the number of trees of that class was noted. 

 The comet-shaped band of plotted points was carefully scrutinized 

 and those which represented abnormally high or unusually low 

 trees for a specified diameter class were thrown out. Then a 

 curve was carefully drawn through the average maximum points, 

 which represented the maximum heights for all diameters of 

 trees of site quality I, and a curve through the minimum points 

 represented the minimum heights for each diameter of site quality 

 III trees. Then the ordinates, on each vertical diameter line, 

 were divided into three equal parts and curves drawn through 

 the two points of division. These curves, therefore, bounded 

 the data for each site and indicated the maximum and minimum 

 heights' for the three site qualities. Curves were finally drawn 

 through the centers of each of the three bands and the average 

 heights for each were read off and tabulated in the volume table. 



♦Graves' "Forest Mensuration," pp. 325-326. 

 Schenck's "Forest Mensuration," pp. 60-61. 

 Schenck's "Forest Management," pp. 16-17. 

 Schlich, Volume III, pp. 102-104. 



