Basal Area 



All thinned plots showed greater basal area increment than the unthinned plots (tables 3 

 and 4). Basal area relations closely parallel those of diameter growth. This similarity of 

 growth is not unexpected because basal area is a function of diameter. The thinned plot on the 

 Pattee Canyon area grew about 56 percent more basal area in 27 years than the unthinned plots , 

 while the West Fork thinned plots averaged 35 percent more basal area increment than the 

 unthinned plot during the 10-year growth period. 



Height 



Larch height growth responded to thinning only in the extremely overstocked stands in 

 Pattee Canyon (table 4). The trees on the thinned plot added 48 percent more height during an 

 11 -year growth period than did those on the dense unthinned checks. On the other hand, trees 

 on the thinned plots (1-4) in the moderately overstocked West Fork stand did not show more 

 height growth than those on the check plot (5). Although the rate of height growth varied some- 

 what in the four thinned plots, no significant trend appeared. 



In contrast to western larch, lodgepole pine crop trees in the West Fork plots responded 

 significantly to thinning by a reduction in height growth. Lodgepole pine crop trees in the 

 thinned plots average 30 percent less height increment than those in the unthinned plots (table 6). 

 The response agrees with findings in an earlier lodgepole pine study. 



Table 6. --Mean 10-year height growth of western larch 

 and lodgepole pine on West Fork 



Treatment 

 and 

 plot number 



EH4 (1) 



EH4 (2) 



Crown (3) 



Crown (4) 



Unthinned (5) 



Feet 



11.7 

 9.7 



11.4 

 8.9 



10.7 



Lodgepole 

 pine 



Feet 



8.9 

 6.6 

 5.8 

 7.5 

 10.3 



Cubic -Foot Volume 



Cubic-foot volume increment increased following thinning in both studies. This increase 

 was much more obvious in the more densely stocked Pattee Canyon area. Trees on the thinned 

 plot grew from a volume 23 percent smaller than the average of those on the check plots in 1932 

 after thinning, to a 19-percent greater volume than the trees on the check plots in 1960 (table 2). 

 The volume increase on the West Fork thinned plots is much more subtle, since the smaller 

 initial total crop -tree volumes on the thinned plots have only approached the crop -tree volume 

 on the unthinned plot during the 10-year growth period. Two of the thinned plots now have about 



^Tackle, D. , and R. C. Shearer. Strip -thinning by bulldozer in a young lodgepole pine 

 stand. Mont. Acad. Sci. Proc. 19: 142-148. 1959. 



9 



