30-Year Results 



By 1965, 30 years after treatment, western larch in the moderately cleaned plot 

 had increased its percentage of the trees in the dominant and codominant crown classes 

 from about 50 to nearly 75 percent- -thereby regaining much of its pretreatment advantage 

 over western white pine (fig. 1). In the heavily cleaned plot, where virtually all 

 larch except very small seedlings had been removed, this species made a surprising 

 comeback and accounted for more than 40 percent of the trees in dominant and codominant 

 crown classes by the time of the 1965 measurement. Reestablishment of lodgepole pine 

 on these cleaned plots was almost nil. Western hemlock and western redcedar made a 

 strong recovery in the understory, especially where the heavy cleaning was done; after 

 only 15 years, these two species totaled more than 7,000 stems there. In the check 

 plot, western larch and lodgepole pine continued to exert complete dominance, and by 

 1965 the western white pine population had been reduced to scattered, suppressed, and 

 declining individuals. 



Posttreatment growth rate of the trees has shown a direct relationship to the 

 intensity of western white pine release. In comparison with the check plot, the accel- 

 eration of diameter increment on released trees resulted in total basal areas that were 

 20 percent higher in the moderately cleaned plot and 40 percent higher in the heavily 

 cleaned plot (fig. 2). Also, height growth of the larger trees was similarly improved 

 (fig. 3). Based on measurements of the tallest 100 trees per acre of each species, 

 white pine at 38 years attained a height of only 13 feet on the check plot compared to 

 46 feet under the moderately cleaned conditions and 54 feet where heavily cleaned. 



500 



250 



500 



1,000 



UNCLEANED (CHECK PLOT) 



MODERATELY CLEANED 



HEAVILY CLEANED 



^1 Dominant and codominant trees 

 I I Intermediate and suppressed trees 



Figure 1 . --Effeot of moderate and heavy cleanings on number of trees per acre ZO 

 after treatment , by Grown class and species ^ Upper West Branch study. 



years 



3 



