200 



3 



g 150 



100 



50 



BURNED 



^ / 



CHIPS 



UNCUT 



50 



u 

 u 



(k: 40-1 

 O 



LJ 

 Q, 



Q. 



LJ 30 



< 



a 



2 



Z 



20- 



10 



B 



/ ,'V'> ^NCUT 



' 11. \ V' 



chips'/ 



1 — I 



5 10 



JULY DAY 



-T- 

 15 



20 



Figure 11— (A) Maximum daily temperatures on 

 burned, ctiips, and untreated surfaces. Litter 

 surface is same as burned. (B) Minimum daily 

 temperatures on untreated, burned, litter, and 

 chip surfaces. Data are from Union Pass in July 

 1979. Burned, litter, and chip surfaces are in the 

 clearcut. Horizontal line for maximum tempera- 

 tures (A) is at 133 °F, a seedling survival 

 threshold. 



Figure 12 — Minimum temperatures at 

 Union Pass on July 10, 1979. The lower 

 row of numbers represents surface 

 temperatures: the upper row represents 

 temperatures at 2 inches above the 

 surface. 



In summary, the results for Union Pass are consistent 

 with those at Lubrecht for the burned and Htter surfaces. 

 Vegetation development for the two treatments is also 

 similar to that at Lubrecht, except slower. Even after 



6 years, ground coverage of vegetation was low (less than 

 25 percent) on both treatments. 



The difference in results for maximum temperatures 

 on the burned and litter surfaces between Coram and 

 Lubrecht can be explained by observations about the pre- 

 treatment vegetation, subsequent vegetation development, 

 and severity of the burns. At Coram the burn was not as 

 hot as the burn at Lubrecht because of the differences in 

 duff moisture (Artley and others 1978; Steele 1980). This 

 situation, coupled with habitat type differences, promoted 

 rapid postburn vegetation development at Coram. By mid- 

 summer of the first year after burning at Coram, a good 

 ground cover of grasses and forbs existed that was quite 

 effective in shading the surface. At Lubrecht the litter 

 surface of the close utilization treatment was disturbed 

 more by ground skidding, which stimulated resprouting 

 and provided conditions for colonization of weeds. At 

 Coram, where a skyline yarder was used, understory 

 vegetation was disturbed differently on the close utiliza- 

 tion treatment where the litter surface was measured. 

 Branches and tops of shrubs and herbs were broken and 

 mashed but not severely damaged. As a result, resprout- 

 ing and regrowth were not stimulated enough to cause 

 rapid growth response, yet coverage was enough to pro- 

 vide a significant number of shaded spots for seedlings. 



Comparison With Expected Results— Other published 

 results reveal some inconsistencies between burned and 

 unburned surfaces. Fowler and Helvey (1981) did not find 

 any differences between temperatures on the burned pile, 

 broadcast-burned scarified surfaces, and the unburned sur- 

 faces on a clearcut in northeastern Oregon. Ahlgren (1981) 

 reports that burned surfaces were warmer for the first 



7 years than were unburned surfaces. After 8 years 

 burned surfaces became cooler, a trend that was attrib- 

 uted to gradual development of shrubs. Our results seem 

 to be consistent with Ahlgren's observation of vegetation 

 development. Temperatures of burned and litter surfaces 

 were similar (both maximums and minimums), yet the 

 amount of vegetation cover and the rate at which it 

 developed significantly modified the differences. 



13 



