D.B.H. 



Figure 1 . — Hypothesis: total monoterpene percentage of lodgepole pine phloem dry weight, as a 

 function of d.b.h., phloenn thickness, and average radial growth. 



The July 31 monoterpene percent of phloem dry weight in 

 trees ranged from 0.03 to 1 .1 percent. Almost 40 percent of the 

 variance (R^ = 0.39) about the mean of 0.238 was explained by 

 the regression of monoterpene percent on the strongly interact- 

 ing independent variables, phloem thickness, growth, and 

 tree diameter (fig. 1). 



The unexpected bell-shaped effect over d.b.h. is somewhat 

 deceptive because there is a rather strong correlation between 

 phloem and d.b.h. The d.b.h. effect is better characterized by 

 the monoterpene trace over the d.b.h. -phloem line of correlation 

 (fig. 2). There it can be seen that monoterpene content reaches 



a maximum at about 13 inches (33 cm) and, although the trend 

 is slightly down thereafter, content at 20 inches (51 cm) still 

 exceeds that for 8-inches (20 cm) trees. 



Component monoterpenes were explored with much the 

 same results as for the monoterpene sum. So, the mathemati- 

 cal form for the sum was adopted for the components and was 

 scaled to the data for each component using weighted (1/Y^ '') 

 least squares (fig. 3). The coefficients for component models 

 were subsequently adjusted to equal, in sum, that for the all- 

 component model. As a result, contents for the sum of compo- 

 nents equal that of the all-monoterpene model at all combina- 

 tions of d.b.h., phloem, and growth. 



4 



