divided by tree height at the poorest aspect. For example, an amplitude of 

 1.82 for advance lodgepole pine means that trees will be 1.82 times taller at 

 the optimum aspect of 31 degrees than they are at the poorest aspect of 211 

 degrees. 



Heights of Subsequent Regeneration — The calculation of heights for 

 subsequent regeneration begins by determining the number of years from 

 the last disturbance to seedling germination. Coefficients for these WeibuU 

 distributions are given in appendix B, table 17. Important variables are the 

 number of years since last disturbance, spruce budworm defoliation after 

 harvest, and species. 



Figure 12 shows cumulative Weibull distributions for the number of years 

 of delay to seedling germination for plots 2-7, 8-12, and 13-20 years since 

 disturbance. The species illustrated is grand fir with no budworm defoliation. 



Equations for predicting heights of subsequent best trees are given in appen- 

 dix B, table 18. A total of 9,239 subsequent best trees were used in these 

 analyses. As with advance regeneration, the most important independent 

 variable is tree age. 



Spruce budworm defoliation history was not important for predicting height 

 of host species. This finding agrees with Carlson (1988), who found that 

 height growth of subsequent regeneration in even-age stands was not affected 

 by spruce budworm and defoliation was light, even though adjacent overstory 

 host trees were moderately to heavily defoliated. 



Increasing residual overstory density reduced heights for all species. Shade- 

 intolerant species, such as ponderosa pine and lodgepole pine, had large 



1.0 H 



A 



B 



0.0- 







5 



10 



15 



20 



Delay to Germination (years) 



Figure 12 — Weibull cumulative frequency distributions for delay to 

 germination for subsequent grand fir regeneration. Curve A is for 

 2-7 years time since disturbance, curve B for 8-1 2 years, and 

 curve C for 13-20 years. 



22 



