ROLE OF FIRE IN CALIFORNIA PINE FORESTS 29 
_ The influence of fire in the California pine region, in interrupting 
the normal development of the forest and in perpetuating the intol- 
erant species through its selective action, is fundamentally the same 
as in the Pacific Northwest, though the species are different. The 
result in California is attained not by occasional catastrophes, as in 
the Northwest, but by the gradual diminution of the tolerant white 
fir and incense cedar, which are easily killed by fire. The intolerant 
pines, with their ability to resist fire, are established under conditions 
unfavorable to their competitors. 
Sumilar manifestations of the importance of recurring surface fires 
in controlling the composition of forests are plainly evident in many 
parts of the western yellow pine belt on the western flanks of the 
Sierras. Since fire protection became effective, white fir and incense 
cedar are appearing in increasing proportion in what, from a mere 
tally of mature timber, would seem to be a western yellow pine 
type. 
; Awhoieli in the study of plant environment little weight has been 
given to fire, even in an uninterrupted state of nature, it has, in the 
California pine region, been a primary force in determining the suc- 
cession of forest types. 
TABLE 16.—Changes in type as a result of protection against fire, as shown by 
comparisons of merchantable stands and advance reproduction 
{as Merchantable | Advance reproduc- 
eee stand tion 
} 
Lassen National Forest: Acres Per cent Acres Per cent 
Wiestennoyellowapitiess <> seso= 6 os = ree ee 199; 600823 22-225. 127, 500 64 
Ip ee eee eee pee ae ee ws oe ee a es YY Le ee 2. S008 ete ae 1115, 000 | 351 
Hod senolespin Geetacetege as ee Pk RE G7 500k | 2 ane 6, 500 100 
ESEUIS Hares wk oe ecm ch nem tere heen ace eS nl eh ST AS LOR OO 8 | er | | Ota SeReS ae 
Plumas National Forest: 
WWesteminvellome pines se slots hs AS | ee ro | a ee 9.9 
PSSDLSE UDR OIRIYSES we See mann c DASE a eee a ae ees ee ee) ee ih Up | Sees Sa 2 | 5 
DUS eat eens eee Fe ee eee |eeee eee {Ss (Peet en en 2a 25. 2 
Miniteies s tee eet cele ret ori tel) oe afec) ed. 18oreiee a 20.8 
BICGHSE ICEL let ee ae es BI hg ek |e 5 2 Ne besa aie ete 39. 1 
(Basis, 51.2 acres.) 
Tahce National Forest: | 
Wicshoriiey Gllovy pinle=sssstys eer y ss tee bower et os aloes. (Galt 4323 hae 36 
TLE WA Ee oe ea te a eee tees Dee pcs seen 64 
(Basis, 10 acres.) 
1 Fifty per cent or more fir in reproduction determines fir type. 4 - 
2 Percentages by number of trees. Percentages by volume of merchantable timber are, for these species, 
reading down: 35, 17, 23, 15, and 12. 
THE PROCESS OF ATTRITION 
The most significant relation between fire damage and site quality 
has been referred to as attrition, that important but often unnoticed 
process that has been going on for centuries in the virgin forest. On 
such a burn as the Ham Station fire, mentioned in connection with 
Table 4, not only was a certain percentage stripped of timber, but 
this area as a whole is reverting to brush, and the brush will in turn 
.< 
® 
erage f, Napa) 
increase the intensity of subsequent fires. Another example already 
mentioned is the Howard fire, which occurred on an area the fire 
history of which is known with a reasonable degree of certainty. 
“This area has been subject for many years to repeated forest fires 
