REGENERATION RESPONSE 



Assuming that HE's and CE's are events with a poten- 

 tial for causing seedling mortality, there should be a rela- 

 tionship between these events and actual seedhng survival. 

 For the sites in this study, the relationship between HE's 

 and CE's and regeneration success does seem to be strong 

 and consistent. 



Lubrecht 



At Lubrecht, the frequency of HE's and CE's (table 8) 

 suggests that first-year survival should be lower on the 

 clearcut than on the understory removal for the first 2 

 years. Douglas-fir and western larch survival (first year) 

 for the 1979 planting was from to 8 percent (table 8) 

 on the clearcut treatment, and greater than 64 percent on 

 the understory removal treatment where no HE's or CE's 

 were measured (Schmidt 1984). 



Survival for ponderosa pine was greater than for 

 Douglas-fir or western larch at about 50 percent on the 

 clearcut and 96 percent on the understory removal treat- 

 ment. Even though the survival was higher for ponderosa 

 pine, the pattern of survival for all species was consistent 

 vnth the expected pattern, based on HE's and CE's. 



First-year survival for seedlings of all species planted in 

 1980 was higher than for the 1979 planting, which might 

 be expected because the number of HE's and CE's was 

 lower than for 1979. The clearcut had the highest fre- 

 quency of HE's and CE's and much lower survival for 

 western larch than for the understory removal. Survival 

 differences were not as dramatic as the previous year for 

 Douglas-fir. Survival of ponderosa pine was not much dif- 

 ferent for any of the treatments except the close utiliza- 

 tion surface in the clearcut. Overall, for all species in both 

 years, survival was not different between the broadcast 

 burn and close utilization treatment, which is consistent 

 with the pattern of HE's and CE's. 



The frequency of HE's during the growing season seems 

 i' better explain the pattern of survival for western larch 

 than do the CE's. For ponderosa pine, CE's seem to 

 better explain the pattern of survival than the HE's. For 

 Douglas-fir, HE's and CE's seem to be about equal in ex- 

 plaining the survival pattern. These results are consistent 

 with our ideas about the adaptability of these three 

 species. Ponderosa pine is known to be more adapted to 

 hot-dry sites and thus may survive the HE's better than 

 the CE's. Douglas-fir, the intermediate of these species, is 

 better adapted to drier sites than is western larch but not 

 as well as ponderosa pine, thus possibly being equally 

 susceptible to HE's and CE's at Lubrecht. Western larch 

 would be expected to be more sensitive to hot-dry sites. 

 Thus, the mortality would likely be the result of the HE's 

 and related moisture stress before the CE's occurred. 



Coram 



The only two comparisons at Coram that can be made 

 are between the burned surface of the broadcast burn 

 treatment and the litter surface of the close utilization 

 treatment within the clearcut. Seedling survival was high 

 (90 percent) on both treatments for all plantings (Shearer 



Table 8— First-year plantation survival data from Lubrecht for 

 ponderosa pine, Douglas-fir, and western larch con- 

 tainer stock planted on clearcut and understory removal 

 treatments. Broadcast burn and close utilization treat- 

 ments were used in the clearcut. Hot events and cold 

 events for these treatments are shown by year. 



Clearcut 



Broadcast 

 burn^ 



Residue 

 removed^ 



Understory 

 removal 



Species 



(percentage survival) 

 Ponderosa pine 

 Douglas-fir 

 Western larch 



Temperature 

 (percentage days) 



Hot events 



Cold events 



Species 



(percentage survival) 

 Ponderosa pine 

 Douglas-fir 

 Western larch 



Temperature 

 (percentage days) 



Hot events 



Cold events 



1979 



48 

 4 

 4 



37 

 26 



1980 



100 

 52 

 8 



23 

 



28 

 8 

 



19 

 42 



60 

 56 

 16 



17 

 3 



96 

 76 

 64 





 



84 

 72 

 68 











^Surface condition was burned. 

 ^Surface condition was mostly litter. 



1980) of Douglas-fir and Engelmann spruce even though 

 HE's were more frequent on the litter surface. Hot events 

 on the litter surface were nearly as frequent as at 

 Lubrecht, but they were rare on the burned surface after 

 the first year. In both treatments at Coram there was 

 more vegetation and debris to pro\ade protection for seed- 

 lings than at Lubrecht. Germination and survival on the 

 seeded spots were higher on the burned surface than on 

 the litter surface. The HE's likely had minimal effect on 

 survival of germinating seedlings, but insufficient moisture 

 was the major cause of mortality (Shearer 1980). How- 

 ever, moisture was less of a limiting factor at Coram than 

 at Lubrecht. The absence of CE's seems to have benefited 

 seedhng survival at Coram. 



Union Pass 



At Union Pass, seedling survival after 5 years was 

 92 percent on the broadcast burn treatment, 46 percent on 

 the close utilization treatment, and 26 percent on the chip 

 spread treatment in the clearcut (Schmidt 1982). Survival 

 for each of these treatments is more closely related to 

 CE's (table 9). The HE's apparently did not influence sur- 

 \aval. The CE's and survival seem to be related to the 

 topographic position of the treatments in a frost pocket 

 rather than to the surface conditions themselves. Stocking 

 on the seed spots and natural regeneration spots also 

 decreased as the frequency of CE's increased. 



16 



