56 BULLETIN 1294, U. S. DEPARTMENT OF AGRICULTURE 
second fire fed on and partially consumed some of these down trees, 
the resultant intense heat killing the standing trees against which 
they had lodged. Where the down trees had fallen among young 
trees the latter were wiped out. This area,in this manner, again 
proves the principle that one fire paves the way for more destruction 
by subsequent fires. | 
Table 21 gives the data on damage to mature timber for both fires. 
The first noteworthy feature is that the loss from burning down is 
greater in the second fire than in the first. In other words, repeated 
hght surface fires over a given area continue the process of attrition 
or even accelerate it. , 
TABLE 21.—Damage to merchantable timber 
[Snake Lake experimental light burning area. First fire, 105 acres; second fire, 126 acres] 
{ 
| 
Loss in trees, by species 
Nature of damage | 
Western 
yellow pine Sugar pine 
fir cedar 
ee ee eee ee 
BURNED DOWN 
No.| Bd.ft. | No.| Bd.ft. | No.| Bd. ft. | No.| Bd.ft. | No.| Bd. ft. 
irstfire! 2-4: £2 5 Gees: 5 | 13,190} 1 120 | '3ib: 6,010.) -O | 282 tse 3 7 
Seconacfire:=- = 755s Tare 5 | 17,740} 5 | 14,980] 7] 9,120; 1 170 | 6 1, 790 
Total 22 toi es 10 | 30,930} 6 | 15, 100-| 10 | 15,130 |. 1 170} 9} 2,560 
HEAT KILLED 
Second fire only_._____-_-- pas N70} <Osi eee Fie 1 | 100) 2:9 WSs oe 6 | 1,360 
BSESEMING == =e ee eee EN 5 4,240 | 38 | 70,600] 3 3, 440 2} 3,800 Oe ee 
Secorid. fires! s2_ - 2. fe hiss: 11} 6, 680) 17} 32,520 | 2 )|- 1, 930 | 64 * 8450-1) Ot see 
Totals eee 4. | Ma 10, 920 "55 (103, 120 5 | 5, 370 arg D2 COU et Oa eset ete 
TOTAL KILLED i ae SS ee 
Pirstfire> 2.94. !s - SSS -3 10 | 17,430 | 39 | 70,720] 6 |. 9,450] 2] 3,800] 3 770} 60 | 102,170 
Second rests. ae 18 | 24, 590 | 22 | 47, 500 | 10 | 11,150} 7 8,620 | 12} 3,150] 69} 95,010 
16 | 20,600 | 9} 12,420) 15} 3,920 } 129 | 197,180 
i 
! 
| 
AVERAGE KILLED PER ACRE | | | 
| 
Higifre ise of toby fe is 9166 f]- Pst yO78) | -sechey rs BO3}- 245-4 RO nietcs 972 
Second fire.-...2:-------- = 195 |---| 377 |---| 89 fens) 68 f=} 25 754 
PS ee ear eS ——= SS ee SS | | —— = ——S 
Average £. f°. a 182 |_| S12 /---) 89) SAL) AT 854 
} | i 
Another important feature is that direct heat killing did not result 
from the first fire but from the second, occurring where trees burned 
down in 1919 lodged against standing living trees and were consumed 
in the 1920 fire. ‘The actual amount of loss from heat killing is not 
particularly striking. It does, however, point to the conclusion that 
some damage of this sort is to be expected if surface fires run over 
an area repeatedly. 
‘The serious loss from insect attacks, induced by the two fires, has 
already been noted in connection with that subject, as have the 
enlargement of fire scars and the formation of new ones. The direct 
loss to merchantable timber from all causes has averaged about 900 
board feet per acre for the two burns. 
er ee 
