ROLE OF FIRE IN CALIFORNIA PINE FORESTS 23 
TABLE 10.—Cwumulative risk to incense cedar from dry rot 
[From U.S. Dept. Agric. Bulletin 871, ‘‘The Dry Rot of Incense Cedar,’’ by J. S. Boyce} 
| 
Basis Percentage of injury 
Average Dry rot | Severe ~ Infec- 
Age class age Trees volume oa Cull Hos 
Sones | vena Number | Per cent | Per cent | Per cent | Per cent 
OO VGHRSHe reset ee re 4 1 0 0 0 0 
41 to 80 years. -~-22.=-1-+ SPE Se 2 ESO. 60 51 1 0 4 6 
SISCOreey Cals 25> = IE oe Se 105 185 3 3 20 38 
121 to 160 years - _-_-- eee eee ee we 2 141 284 4 2 29 46 
161 \to.200 years—~ - .-4 =. 2: aS eS eae 180 233 10 | 12 42 61 
ANON AAO CALS Sn eens ene re er ee as 223 118 22 30 61 i 
DEMONS CRESS?< SR ee Se eee ee 259 94 44 52 79 83 
Ze bia) Seah GENS SEES Sa ee eee 296 49 | 62 67 88 92 
PALO DOURMCRES rb oe eS eee 334 19 | 67 79 90 90 
SEISLO ADO VORTS sia) ber SN oe est 37 4 82 75 100 100 
AUIBLOISAULY CRBS. oe eh aaa oe Sede coe 436 2 | 5 0 100 100 
Cy Te BOREAS RS ee dea OS [=~ 7 Sheers |e ck ~ ea ee Oona a otsevee 
EGO ODS ee es ae ee | 172 |---------- 15 17 42 56 
This study further showed that of 1,075 typical trees dissected and 
examined 60.1 per cent had fire scars. On fully half of these trees 
the scars had not healed over. Of 656 trees infected with dry rot 
67.1 per cent had been infected through fire scars. The importance 
of these wounds as a point of entrance for the fungus is illustrated 
by the fact that 67 per cent of all trees with fire scars were infected. 
Of the cases which resulted in serious cull, defined by Boyce as loss 
of one-third or more of merchantable volume, fire was responsible for 
the entrance of the fungus in 84 percent. Thus all other causes com- 
bined resulted in only 16 per cent of the instances of serious cull. 
The tendency to decay through new fire scars or through old wounds 
enlarged by fire is likely to be more serious in the older stands than 
it is in young stands, as the studies already cited show; for, although 
infection of trees may take place at a comparatively early age, serious 
destruction of the heart wood seldom appears at an age below 160 
years. 
_ While the actual amount of loss from decay induced by fire is not 
given by either author quoted, it is clearly shown that fire is the prin- 
cipal indirect oe causing cull in white fir and incense cedar in the 
virgin forest. This is of special interest in view of the fact that these 
two trees, which form an appreciable part of the timber stand in the 
ine region of California, have come to be classed as inferior both by 
umbermen and by foresters, and not because of inferior technical 
loge of the wood, but rather because of the greater frequency of 
cull. 
The relation of decay to fire injuries is not, however, of signifi- 
cance only for the species regarded as inferior. Fire scars on the 
more valuable pine are an important source of infection, and though 
the degree of decay here is very much less than in white fir and 
incense cedar, in one typical instance in western yellow pine it has 
amounted to a cull of 1.7 per cent, due to rot directly traceable to 
fire scars. Table 11 shows a similar case. This table gives the 
actual commercial loss of volume from sie for all five of the prin- 
cipal species, as this appeared on extensive Government timber sales. 
