Close comparison of the tables reveals that certain combinations of di- 

 ameter and age show higher predicted growth on poor sites than on good. This 

 apparent paradox exists for two reasons: First, small trees of an advanced age 

 normally are not found on good sites. If present, they are suppressed or dam- 

 aged and their current growth rate is slow. The same size trees of similar 

 age on a poor site are likely to be average trees maintaining reasonably good 

 growth. Second, large trees of a young age are not normally found on poor 

 sites. If present, they are unusually thrifty trees, probably open-grown and 

 increasing in diameter faster than the average tree for that site . On the 

 other hand, that same combination of age and size on a good site could rea- 

 sonably be an average tree adding only average growth. It is evident, then, 

 that comparisons of individual tree growth between sites is meaningless until 

 actual measurements of dominant and codominant trees from different sites are 

 entered in the table and the growth predictions derived. 



Use of the tables requires knowledge of the age and diameters of the 

 trees in question together with the broad site classification. Site can be 

 read from figure 1 by entering the average height and age of a few dominant 

 and codominant trees from the area . 



yl6E CVeors) 



Figure 1 .--Height of dominant and codominant trees of average breast- 

 high diameter by site groups. (After Meyer, Walter H. 1938. Yield 

 of even-aged stands of ponderosa pine. U. S. Dept. Agr . Tech. Bui. 

 603, 60 pp . , illus .) 



2 



