Height growth of subalpine fir was influenced by degree 

 of overstory removal and several other variables. Trees 

 grew best when all the overstory was removed but grew 

 least in the control and partial removal. Increasing basal 

 area change and prerelease diameter growth also resulted 

 in better height growth (figs. 1, 3). We did not detect a 

 significant influence of budworm on subalpine fir height 

 growth (table 3). This was the strongest height growth 

 model; even so, the CD was only 0.27. 



Diameter Growth 



Models for predicting 12-year postrelease diameter 

 growth were much stronger than for height growth and 

 showed the release from competition. Ten-year radial 

 growth preceding treatment (fig. 4), d.b.h. at time of treat- 

 ment, and degree of overstory removal were significant in 

 the model developed for Douglas-fir (table 4) and the CD 

 was 0.53, far larger than for the height growth model of 

 this species. Larger, faster-growing trees where all the 

 overstory was removed grew best. Budworm had no de- 

 tectable influence. 



Posttreatment diameter growth of Engelmann spruce 

 increased with increasing prerelease radial growth and 

 degree of overstory removal (table 4, fig. 4). We did not 

 detect any influence of basal area change, budworm, or 

 other variables tested. The CD for spruce was 0.45, also 

 much larger than for the height growth model. 



Diameter growth of subalpine fir responded positively 

 to increasing basal area change and 10-year prerelease 

 radial growth (table 4, fig. 4). The coefficient of multiple 

 determination was 0.50. Oddly enough, trees with 

 smaller crown ratios responded better than those with 

 larger crown ratios. Degree of overstory removal had no 

 influence on diameter growth. Again, budworm did not 

 significantly influence postrelease diameter growth of this 

 species. 



Mortality 



Chi-square tests indicated that cutting type and species 

 significantly influenced postharvest mortality (table 5). 

 The interaction was nonsignificant. Percent mortality for 

 all species combined, since the study began in 1973, was 

 nearly the same — 13 to 14 percent — among the complete 

 overstory removal and control treatments (table 6). In the 

 partial removal, however, mortality was substantially 

 greater — about 25 percent. Among species, mortality was 

 highest for Douglas-fir at 22 percent but about 13 percent 

 for the subalpine fir and spruce. Average mortality over 

 all species and treatments was about 16 percent for the 

 12-year period, or 1.3 percent per year. 



Table 3 — Regression equations predicting natural log of 1 1-year post release height growth of Douglas-fir, 

 Engelmann spruce, and subalpine fir 



Variable Coefficient T Probability 



Douglas-fir 



Basal area change 

 10-year radial growth 

 WSB defoliation 

 Intercept 

 R-square 



Error mean square 



F for regression (Probability) 



Basal area change 

 10-year radial growth 

 WSB defoliation 

 Intercept 

 R-square 



Error mean square 



F for regression (Probability) 



10-year radial growth 

 Basal area change 

 Overstory removal 1 

 Overstory removal 2 

 Overstory removal 3 

 Intercept 

 R-square 



Error mean square 



F for regression (Probability) 



0.210 

 6 437 

 -.012 

 -.498 



0.20 

 1.83 

 11.11(0) 



Engelmann Spruce 



3.972 



-.171 



5.562 

 .187 



-.372 

 .692 

 .445 



-.826 



0.15 

 2.37 

 12.37(0) 



Subalpine Fir 



0.27 

 1.82 

 15.85 



2.81 

 5.10 

 -2.69 

 -2.02 



3.38 

 -60 



6.96 

 2.35 



-1.16 

 2.37 

 1.34 



-5.13 



0.006 

 



.008 

 .050 



0.001 

 .545 



.020 

 .248 

 .019 

 .182 



6 



