43 

 (2) L'amage to Merchantable Timber thru Heat Killing 



Heat killing is the form of damage resulting from 

 crown fires. Although crown fires are uncommon' in the 

 coniferous forests of the Sierra region, they have been 

 known to occur, causing considerable damage over exten- 

 sive areas. Thus, in September 1917. 5^0 acres were 

 burned on the Shasta National I'^orest (Howard Fire) on 

 250 acres of which the timber was entirely destroyed. 

 Also, in the Palm Creed Fire in l897. on the Grater Nat- 

 ional Forest in Oregon, a crown fire killed all but a 

 few scattered trees on an area of over 8OO acres. This 

 occurred in a pine-fir forest similar to those of Nor- 

 thern Galifornift. 8, B. Show in making ^ study of five 

 typical fires (mentioned above) found that 3^ of "the 

 total area observed had been heavily burned by local 

 or general crown fires. The loss by heat killing on 

 the areas thus heavily burned, averaged 8,530 board feet 

 per acre, and had a stumpage value of $13. 5i P^r acre. 



While genuine crown fires seldom occur, intense 

 local burning is common'. Southern and western slopes 

 dry./more quickly than other exposures, as do also the 

 heads of draws. It is here that light surface fires 

 often flare up suddenly and destroy large trees. West- 

 ern yellow pine and sugar pine suffer less from heat 

 killing than do the firs, cedara and western white pine. 

 This is due to the fact that the bark is relatively 

 thicker, the base of the crown is higher, the foliage 



