Steele, Brian M.; Cooper, Stephen V. Predicting site index and height for selected tree 

 species of northern Idaho. Research Paper INT-365. Ogden, UT; U.S. Department of 

 Agriculture, Forest Service, Intermountain Research Station; 1986. 16 p. 



Forests in northern Idaho are capable of supporting as many as 1 different tree 

 species on a given site. Comparing site indexes of species across a variety of sites is 

 one method of assessing which species to favor in stand management. From plots 

 across the spectrum of forest environments, site indexes (50-year index age) of species 

 pairs (26 combinations of a possible 36 total combinations for nine species) were shown 

 by regression analysis to be linearly related. Site index values of one species were able 

 to explain between 33 and 85 percent of the variation in the site index of associated 

 species. Because land managers are interested in more than comparative heights at an 

 arbitrary index age, we developed equations for predicting the height of species A from 

 the predictor variables, site index of associated species, and the age of species A. 

 Graphical solutions of these equations and site index curves are provided for those with- 

 out ready access to mathematical solutions. 



KEYWORDS: site index predictions, height growth predictions, northern Idaho 



