OTHER POSSIBLE BASES FOR SITE QUALITIES 



387 



Site qualities, whether three or five in number, must be adapted 

 to the range of actual yields of the species to be measured. Different 

 species require a different range of site factors. The conifers thrive 

 in soils too poor for hardwoods; hence quality I for pines may be quality 

 II for oaks. 



The adoption of a common standard of site index for species with the 

 same range of soil requirements is desirable. One suggestion is to 

 classify the trees of the country into groups, based on their total growth 

 in height at a definite age. This principle is illustrated by the follow- 

 ing table, in which four site classes are made for each group, based 

 on even gradations of total height for dominant trees of the same age. 



TABLE LX 



Standards of Site Classification Based on the Height of Tree at 100 Years 



A standardization of this character serves the double purpose of 

 coordinating the j-ield tables for species of similar growi:h habits, and 

 furnishing the simplest basis for site classification during forest survey. 



297. Other Possible Bases for Site Qualities. Medwiedew's Method. A 

 method of site classification suggested by Medwiedew, a Russian, and applied by 

 Hanzlik to Douglas fir is as follows : 



A site factor is calculated by the formula, 



Site factor = 



cXh 



when c= basal area on the average acre; 

 /i = average height of stand; 

 n = age of stand. 



These so-called site factors may then be grouped to represent different site 

 qualities, all factors falling between certain limits indicating quality I, etc. This 

 basis is not consistent as an indication of site, since it is nothihg but the mean annual 

 growth of the stand in a different form. If / = form factor, then, c/i/= total cubic 



chf 

 volume, and — = mean annual growth of stand. As mean annual growth varies 



n 

 with age as well as site, it cannot be substituted for either volume or height as an 

 absolute basis of classification. 



