201 : M M I M M U U \ i : 1 



20 40 60 80 100 120 140 160 180 

 AGE OF PREDICTED SPECIES, YRS 



Figure 16.— Western larch at site 

 index 50 is used to project the 

 heights of Douglas-fir, 

 Engelmann spruce, grand fir, 

 lodgepole pine, and western 

 white pine; heights of the 

 associated species are projected 

 over their sampled age ranges. 



40 60 80 100 120 140 160 180 200 



AGE OF PREDICTED SPECIES, YRS 



Figure 17.— Western larch at site 

 index 70 is used to project the 

 heights of Douglas-fir, 

 Engelmann spruce, grand fir, 

 lodgepole pine, and western 

 white pine; heights of the 

 associated species are projected 

 over their sampled age ranges. 



H 

 U. 



I-' 



I 



o 



LU 

 I 



Q 

 LLI 

 1- 



Q 

 Ul 



oc 



Q. 



140 

 120 

 100 



7^ 80 



60 













































































































































































































































































































Lv 



















































































































































































D 



F 







































































































































































































































































































































































































































































































































































































































































































f ! 



























































J 























































40 60 80 100 120 140 160 180 

 AGE OF PREDICTED SPECIES, YRS 



Figure 18.— Western white pine 

 is used to project the heights of 

 Douglas-fir and western larch; 

 heights of the associated 

 species are projected over their 

 sampled age ranges. 



200 



with our projection of Douglas-fir height growth gener- 

 ated from observed Engelmann spruce site index. 

 Despite the better statistics for Engelmann spruce than 

 for western larch equations (table 3), comparison of 

 figures 19a to 19b shows Engelmann spruce site index 

 values to be poorer predictors of Douglas-fir height 

 growth. There is a greater discrepancy between the 

 predicted Douglas-fir height growth curve and the 

 "actual" Douglas-fir height growth curve of Monserud 

 when using Engelmann spruce as a predictor than when 

 using western larch. 



Site index and height projection comparisons are 

 useful tools in choosing the best species for a site. Other 

 factors such as stocking, timber value, optimum rotation 

 age, susceptibilty to insect attack, and disease resistance 

 must also be considered. For instance, although western 

 white pine and grand fir are generally projected to be 

 the fastest growing species on a given site, the land 

 manager may favor the relatively slower growing 

 Douglas-fir or western larch because of the susceptiblity 

 of western white pine to blister rust and the lower 

 timber value and higher disease risk of grand fir. 



10 



