LODGEPOLE PINE 



LEADER ELONGATION (CM) 



1975 1976 1977 197B 



GROWING SEASON 



PONDEROSA PINE 



LEADER ELONGATION (CM) 



1975 1976 1977 1978 



GROWING SEASON 



DOUGLAS - FIR 



LEADER ELONGATION (CM) 



4-FT SCALP 11 " 

 10 - 



J-FT SCALP 9 " 



7 - 



6 - 



5 - 



1975 1976 1977 1978 



GROWING SEASON 



Figure 6.— Leader elongation for species and site 

 treatments during the first four growing seasons. 



Frost Damage 



A severe frost in June of 1976 did not directly cause 

 mortality in this study, but frost was credited with 

 preventing 19 percent of the Douglas-fir seedlings from 



Figure 7.— Grouse Creek study site in 1984 

 after 10 growing seasons. 



making leader growth during the second growing season. 

 Of the Douglas-fir seedlings, 22 percent in both 2-ft and 

 4-ft (0.61- and 1.2-m) scalps and 14 percent in dozer 

 strips were frost damaged severely enough to prevent 

 leader growth. The extent of frost damage to Douglas-fir 

 on the three aspects was similar. This frost damage may 

 have reduced the fifth-year mean heights of Douglas-fir, 

 but had minimal effects on the comparison of site treat- 

 ments. The frost had no apparent effect on the two pine 

 species. 



DISCUSSION AND CONCLUSIONS 



There is a contradiction on a site like Grouse Creek 

 where we have potential for high timber productivity yet 

 regeneration is so extremely difficult. This seemingly 

 illogical situation can be explained by two factors 

 (Running 1982): (1) the microclimate changes when a site 

 is clearcut, and (2) physiologically, mature trees are more 

 tolerant of temperature and moisture extremes than are 

 young seedlings. Since clearcutting, elk sedge has 

 expanded to use most of the available summertime mois- 

 ture resource, considered to be the major limiting plant 

 growth factor on the site. So, to allow tree seedlings a 

 share of the moisture, the elk sedge coverage must be 

 decreased. 



Lodgepole and ponderosa pine responded more to the 

 larger scalps than did Douglas-fir. Height growth on the 

 4-ft (1.2-m) scalps and dozer strips was superior to that 

 on the 2-ft (0.61-m) scalps for both pines, but the differ- 

 ences in height growth for Douglas-fir were not statisti- 

 cally significant. At the end of the study the differences 

 in height growth on the three site preparations were 

 widening at an increasing rate for the pines. The growth 

 rate for Douglas-fir on the dozer strips was increasing at 

 a slightly faster rate than on the 4-ft and 24t scalps. 



The chances of seedling survival were higher on the 

 dozer strips and 4-ft scalps than on the 2-ft scalps for all 

 three species. 



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