Response of residual trees in relation to tree size. --Stand structure and size and vigor 

 of trees influence stand growth. In this study, growth response was related to initial tree size. 

 Table 2 shows that an Engelmann spruce tree 8.1 inches d.b.h. at logging reached 10 inches 

 d.b.h.--a 1.9-inch increase in diameter- -in 30 years. On the other hand, a 20.6-inch tree at 

 time of logging grew to 25 inches in 30 years --a 4.4-inch diameter increase. Thus a prepon- 

 derance of large trees in the residual stands helps to develop good stand growth. The same 

 relationship is shown for subalpine fir in table 3 . 



Response of residual trees in relation to tree vigor . --A preponderance of good and fair 

 vigor trees also influenced the diameter growth of the residual trees (table 4). More than two- 

 thirds of the spruce trees in the cutover stand showed fair to good vigor. Differences between 

 mean growth for vigor classes were significant at the 1 -percent level. Further, a covariance 

 analysis showed that the regression coefficients of 5-year diameter increment on crown length 

 were significantly different among dominance classes. Vigor classes used in the field were 

 based upon a vigor classification developed previously for western larch and Douglas -fir 

 trees. ^ Since bark characteristics shown in the classification did not apply, they were not used; 

 however, all other criteria were applied and proved useful in classifying the Engelmann spruce 

 and subalpine fir trees. 



Table 2 . - - Diameter breast high outside bark of Engelmann spruce trees 

 30 years before logging and at 5 -year intervals after logging ^ 



30 years : 

 before : 







Years after logging 







logging : 







5 



: 10 : 15 : 20 : 



25 



: 30 2 



Inches 



7.4 



8.1 



8.2 



8.4 



9.0 



9.4 



9.6 



10 



8.1 



8.9 



9.0 



9.3 



9.9 



10.3 



10.5 



11 



8.7 



9.8 



9.9 



10.2 



10.8 



11.2 



11.5 



^? 



9.3 



10.6 



10.7 



11.1 



11.7 



12.2 



12.5 



13 



10.0 



11.4 



11.6 



12.0 



12.6 



13.1 



13.5 



14 



10.6 



12.3 



12.5 



12.9 



13.5 



14.0 



14.4 



15 



11.3 



13.1 



13.3 



13.8 



14.4 



14.9 



15.4 



16 



11.9 



13.9 



14.2 



14.6 



15.3 



15.9 



16.4 



17 



12.6 



14.8 



15.0 



15.5 



16.2 



16.8 



17.4 



18 



13.2 



15.6 



15.9 



16.4 



17.0 



17.7 



18.3 



19 



13.8 



16.4 



16.8 



17.3 



17.9 



18.6 



19.3 



20 



14.5 



17.3 



17.6 



18.2 



18.8 



19.5 



20.3 



21 



15.1 



18.1 



18.5 



19.1 



19.7 



20.4 



21.3 



22 



15.8 



18.9 



19.3 



20.0 



20.6 



21.4 



22.2 



23 



16.4 



19.8 



20.2 



20.8 



21.5 



22.3 



23.3 



24 



17.1 



20.6 



21.0 



21.7 



22.4 



23.2 



24.2 



25 



17.7 



21.4 



21.9 



22.6 



23.3 



24.1 



25.2 



26 



18.4 



22.2 



22.7 



23.5 



24.2 



25.0 



26.1 



27 



(See footnotes at end of table, page 6) 



^ Roe, Arthur L. A preliminary classification of tree vigor for western larch and 

 Douglas -fir trees in western Montana. U.S. Forest Serv. , North. Rocky Mountain Forest & 

 Range Expt. Sta. Res. Note 66, 6 pp. , illus. 1948. 



5 



