. Table 5— Hot events (percentage of possible days) for the overstory treatments at several study 

 sites. Data represent the May through October period for 1 to 7 years after treatment. 

 Data for the litter surfaces on the clearcut were used when they were available. If not, 

 data from the burned surface were used. 



Years after treatment 

 Overstory 



Study site treatment 1 2 3 4 5 6 7 



Percentage of possible days 



Lubrecht 



Uncut 



1 







2 













Understory removal 

























Shelterwood 



14 



16 



25 













Clearcut 



28 



37 



23 











Coram 



Uncut 



2 





















Clearcut 



36 



27 



23 



29 



29 



6 



1 



Union Pass 



Uncut 





















Clearcut 













65 





In summary, the clearcut treatment on the Lubrecht site 

 creates conditions with a high potential for seedling mor- 

 tality due to high and low temperatures. The shelterwood 

 treatment had a high potential due to high temperatures 

 but not to low temperatures. The residual stand canopy in 

 the shelterwood is open enough to let incident radiation 

 warm the surface, yet it is dense enough to hold heat in at 

 night, slowing radiational cooling. Maximum and minimum 

 temperatures in the understory and uncut treatments 

 typically are not high enough or low enough for potential 

 seedling mortality. Figure 5 shows the maximum and 

 minimum temperature relationships for each treatment on 

 a typical summer day. 



Other Sites— Only data for the clearcut and uncut treat- 

 ments are available on the other two sites. Data from the 

 Coram and Union Pass study sites also demonstrate that 

 clearcutting results in significantly warmer and colder sur- 

 face temperatures. Data on HE's at Coram and Union 

 Pass (table 5) are comparable to the results observed at 

 Lubrecht. The potential for seedling mortality (due to high 

 temperatures) is quite high on the clearcut and low in the 

 uncut stand. The frequency of HE's is high (65 percent) at 

 Union Pass; only data for the month of July are available. 

 Logging significantly increased the potential for seedling 

 mortality at Coram and Union Pass. 



MAX 



MIN 



133°F 



CLEARCUT 



SHEL TERWOOD 



UNCUT 



UNDERSTORY 

 REMOVAL 



Figure 5 — Daily maximum and minimum surface temperatures (°F) by overstory treat- 

 ment at Lubrectit, August 29, 1978. 



8 



