100 



80 



60 



40 



20 



WESTERN 

 WHITE PINE 



WESTERN 

 REDCEDAR 



GRAND FIR 



WESTERN 

 HEMLOCK 



^1 Over 0.5 inch d.b.h. 

 { I Under 0.5 inch d.b.h. 



10 20 30 10 20 30 10 20 30 

 YEARS SINCE STUDY BEGAN 



10 20 30 



Figure 5. — Percentages of all trees in the dheck 'plots that were more than or less than 

 0.5 inch d.b.h. at 10-year intervals, by species. Lower Sands Creek study. 



Western redcedar was poorly represented on these plots initially, and remained so. For 

 the first 10 years after measurements were begun, sufficient light was transmitted 

 through the overstory trees to permit moderate growth of the young trees. Thereafter, 

 increasing shade reduced the height increment of all species to insignificant amounts 

 (fig. 6). 



On the area that received release and cleaning treatments, the numbers of western 

 white pine and western redcedar that had been left remained about the same for the first 

 10 years, but western hemlock and grand fir again showed up in striking numbers (fig. 7). 

 It is probable that much of this apparent reinvasion resulted from seedlings that had 

 been ignored during the cleaning operation. By the end of the 30-year period of study, 

 western hemlock and grand fir comprised 2,000 of the 2,900 trees per acre then present, 

 although few reached a position of dominance. 



Based on heights of the best trees of each species, western white pine responded 

 very well to the preferential cleaning treatment and grew more than twice as fast as 

 its associates (fig. 6). Western redcedar was unable to exploit its initial advantage, 

 barely managing to keep pace with grand fir and western hemlock. 



9 



