TABLE WITH SITE CLASSES BASED ON HEIGHT GROWTH 403 



60 feet, following the suggestion of Roth as an example of class C in 

 height classification (Table LV, § 296), and with these guiding 

 points the curves limiting the three classes were drawn by Baur's 

 method. 



6. The yield of all plots in a single site class are then plotted on 

 cross-section paper whose base or horizontal scale is age, and whose 

 vertical scale is volume. From these data, a curve of average yield 



70 80 



90 100 110 120 130 1.40 150 160 170 180 199 

 Age. Years 



Fig. 85. — Curves of yield obtained by averaging the yields of plots whose height 

 " growth has placed them in the same site class. The final curves smooth off 



irregularities in these averages. Second growth Western Yellow Pine, California. 



S. B. Show. 



based on age may be drawn from which the yields for the site class 

 for each decade or five-year period are read. A separate curve is plotted 

 for each site class. The yield table finally shows the average yields 

 based on age for each separate site class. 



