3 Be BULLETIN 1294, U. S. DEPARTMENT OF AGRICULTURE 
This form of damage is always strikingly apparent immediately 
after a fire, for the fire-blackened trees or those with brown foliage 
stand out in strong contrast to the living forest. 
CONTROLLING FACTORS 
In the virgin forests of California, the severity and extent of heat 
killing varies greatly, depending on a wide range of factors. In the 
field study of direct damage to merchantable timber, 15 large fires 
with an aggregate area ol 52,100 acres were carefully cruised long 
enough after the fire so that the amount of fuel and. the extent of 
damage could be accurately related. The facts are given briefly in 
Table 3. 
TABLE 3.—Direct damage to merchantable timber by heat killing 
Oniled | Val 
pear ille alue 
Name of fire and type of cover Area Area, heavily per acre | of loss 
g on total | per acre! 
area 
: Acres Acres Per cent | Board feet 
Ham Station—Bear clover, and brush..-._...______- | 9, 485 310 308 550 $0. 54 
Bear River—Bear clovers:2-. 222. 2200 £8 3 Se Ae 500 7 1.4 38 08 
Slate Mountain—Bear clover .__.__-.__2_--_--2_-s--- 350 Jee oe Abele eee 50 ~10 
Butler Meadows—Some brush_____--______-__-______ 1, 120 18 1.6 230 . 66 
Piloti@reek—Someibrush]2 2. 35 Sa ee eee 380 10 2.6 250 25 
Witte: Eorse——Some -brush®.2 2 ee ee ee 20, 500 2, 300 AT? 1, 590 3. 90 
Howard—-Heavyabrushe 6 aks. Bue Oe ee ee 700 700 100. 0 10, 900 16. 40 
Hoey Heaw,y; -DruShsene eee os eee ee 410 410 100. 0 2, 820 8. 50 
Soda @reck—=El Ca Vey DLUSH 2. 2 ee es Obrien 1, 200 480 40. 0 2, 340 5. 50 
Ferris Creek—Heavy brush___.__._______________--_-- 4, 635 2, 220 47.9 3, 360 6. 90 
WiGeG=— ML GLOPDRUSH sai. en ie eee ape Me ee 2, 000 30 15 220 . 66 
Quincy Junction—Medium brush__________________- 200 30 15.0 2, 100 4. 50 
Moffitt Creek—Medium brush_-_-________.__________- 10, 000 1, 210 12.1 1, 425 2. 90 
Lassen- Walker—Heavy brush__________-________-.__- 220 220 100. 0 3, 350 5. 50 
Boardman Ridge—Medium brush_________________1- 400 40 10:0 1, 390 2. 03 
Average (welghted):.2 122 ese. SRR sieve fe aola| EM sh opal Se 1.8 1, 570 3. 32 
“ABO ea | (ee ae ee ear er mee ercipe nee eee ee CaN 52, 100 
1 Based on the average minimum stumpage prices of the Forest Service for this district, which for the 
five species concerned are: Sugar pine, $2.75; western yellow pine, $1.75; Douglas fir, $0.75; white fir and 
smcense cedar, $0.50. 
By far the most important factor in heat killing is the amount of 
inflammable material on the forest floor, such as litter and duff, and 
the understory ‘of grass, weeds, undergrowth, and reproduction. I 
the individual fires are examined in detail, it is seen that the most 
serious damage has resulted where a large amount of brush was 
present under the timber stand. The least damage was found where 
the inflammable material consisted of needles, twigs, and bear clover.® 
Topography is a factor of great importance. Fires starting near 
the bottom of a slope gather momentum as they travel uphill, and 
the timber on the upper slopes and ridges must bear the brunt of 
the increased intensity of the flames. Gulches and saddles often 
tend to act as funnels for the wind, developing intense heat and 
causing great damage to standing timber. On large plateaus where 
there is no topographic interference to the uninterrupted sweep of 
the wind, fires are often fanned to intense heat over a wide front, 
resulting in heavy damage to timber. 
6 Bear Clover (Chamaebatia foliolosa) is a low-spreading shrub which burns very rapidly, but has only 
a little fuel substance, and therefore burns and retains heat for oniy a short time. 
