8 



JOURNAI, OF FORESTRY 



in the latter studies the age-height tables are based more on young 

 than on old trees ; with more data for old trees they would probably 

 conform even better to the site class curves here presented : 



The limits for each site class are given by decades in Table 1 : 



Table 1. — Site class limits (age-height) for southern upland hardwoods, with 

 even 20- foot intervals at 100 years. 



The curves and the table read from them are not in terms of any 

 one species, but of all the indicator species measured. While 

 it is evident that the classification does not allow for the specific dif- 

 ferences in growth rate, this is not as serious an objection as might 

 be supposed. Among the interesting points brought out by the curv- 

 ing was the comparative similarity in height growth of the indicator 

 species ; the difference in height between dominant poplars, black oaks, 

 and chestnuts in an even-aged cove stand, for example, or between 

 chestnuts and chestnut oaks in a ridge stand, is relatively small, and 

 is not great enough nor consistent enough to raise, lower, or change 

 the direction of the curves appreciably. Perhaps this is due simply to 

 the relatively wide range in height for a given age allowed for each 

 site; in the six-class series the differences between maximum and 

 minimum height at 50 years is 15 feet, while for the three-class 



