28 BULLETIN 1294, U. S. DEPARTMENT OF AGRICULTURE 
Table 14, taken from this area, illustrate this relative resistance of the 
principal species to light fires. In short, the western yellow pine is 
found to be the most fire-resistant species, cedar and ne highly sus- 
ceptible, and sugar pine probably close to western yellow pine in its 
resistance. The relative order of the species is found to be similar 
to that for mature timber in resistance to crown injury. 
TABLE 14.—Relative susceptibility to fire injury of different species of young 
growth less than 4 inches in diameter 
[White Horse fire, 1920, Modoc National Forest] 
Total killed Total alive 
Species (basis) 
Westen. yellow. pine: 2224 — pet ya Se Ce 485 363 75 122 25 
Sugar pine. |. (Peprd -oy i 74t - bc et cect Vo ee > 5 4 80 1 20 
WihiLedhin sa Pee Seti ear ee ipa staan 126 123 98 3 2 
Inycense’cedarss 2s the) Sebi Saye ees 54 54 100 0 0 
A-similar study, the Castle Rock light burning, was started in 1911 
in the Shasta National Forest and continued for several years. On 
this area Douglas fir is the associated species in place of white fir. 
The results of the investigation showed western yellow pine to be the 
least susceptible, incense cedar the most susceptible, and Douglas fir 
intermediate. It is noteworthy that these results are in line with 
the results obtained by the California Forestry Committee (6) in 
their hundred per cent survey ot light burning on the Moffitt Creek 
area in the Klamath National Forest, as shown in Table 15. 
TABLE 15.—Relative susceptibility of young growth to fire injury 
[Strip, 2.6 acres; Moffitt Creek light-burning area, Klamath National Forest; burn of June, 1922] 
Surviving trees, by height groups 
Species | = 
14 to 3 feet | 4to6feet | 7 toS8feet | Over 8 feet Total 
No. | P.ct.| No. | P.ct.| No. | P.ct.|° No. | P.ct.| No. | P.ct. 
Western vyellowapines= 2-2) eos ee 215] 1.9] 184] 3.3 33 | 12,1 62 | 42.0} 494 8.1 
St ParspIne at. eras 2S as Dee Ae | See ee y fel ER ae ee el ee ee foe CRE 6 5.0 
I OUP LAS shite aos ee a ge Nc ae ae ete 1a eee oe ee eee eer 4 | 25.0 24 4.2 
Incense cedars 1362 52) be ee te 148 Se. © OAL oad Soles aires: 6 }. 16.7 | ~211 1.4 
Total, all'speciess j. h ae nee tae S19) | ds 248 | 3.3 367} live 72 | 38.9 | 735 6.0 
EFFECT OF FIRE ON FOREST COMPOSITION 
The investigations of Hoffman (10) and others have shown that 
fire has been the dominant factor in the Douglas fir and western 
white pine regions in controlling the present composition of the vir- 
gin forests. Douglas fir and white pine, the intolerant species in 
their respective regions, are perpetuated in the mixed virgin forests 
by the elimination of the other species through crown fires. If the 
forest were allowed to develop uninterrupted by fire, it would finally 
consist of the tolerant hemlock, cedar, and white fir, which are able 
to reproduce in the shade of the old forest. Douglas fir and western 
white pine would be relegated to very minor positions in the stand. 
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