402 



NORMAL YIELD TABLES FOR EVEN-AGED STANDS 



4. Divide the space between the maximum and minimum curves, on 

 each ordinate, into arbitrary spaces of equal magnitude, corresponding 

 to the number of site classes established, and connect the points so found 

 by curves. 



5. The numbered plots whose height falls in each division of the 

 chart are assigned to the indicated site quality. Owing to variables 

 affecting yield, some of the plots in a lower site class may exceed the 

 growth of plots whose site class is better. 



30 



10 50 



Age, yeaxs 



60 



70 



Fig. 84. — Method of separating plots into three site qualities based on the height 

 attained by dominant trees in the stand, plotted on age of stand. Jack Pine, 

 Minnesota. 



The height of dominant trees on 131 plots of jack pine, plotted on 

 the basis of age, is shown in Fig. 84. By this method (Baur's), the 

 positions of the maximum and minimum curves determine that of the 

 curves separating the site qualities. One or two plots with abnormally 

 rapid or slow growth must not be permitted to influence unduly the 

 position of these outer curves. With height, the true position of the 

 boundary curves can be found with greater certainty than if volume is 

 used originally as the basis of classification. In this figure, the average 

 heights of qualities I, II and III at 100 years were taken as 90, 75 and 



