30 



SITE INDEX 



20 



10 



BO 

 70 



60 



50 

 40 



10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 



AGE 



Figure 59 — Quadratic mean diameter vs. age for western larch precommercial 

 thinning to 250 trees per acre at 20 years and commercial thinning from above 

 to 100 trees per acre at 50 years in Inland Northwest forests. 



30 r 



SITE INDEX 



10 



80 



70 



60 



50 

 40 



10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 



AGE 



Figure 60 — Quadratic mean diameter vs. age for western larch precommercial 

 thinning to 250 trees per acre at 20 years and commercial thinning to 100 trees per 

 acre at 50 years such that the mean d.b.h. before and after thinning is the same. 



50 



