26 BULLETIN 1495, U. S. DEPARTMENT OF AGRICULTURE 
type is the only one in which the annual rate of loss has been kept 
near 0.2 per cent. The other main forest groups average a lower 
rate of loss than the northern group, though the relation between 
types is substantially the same. 
TaBLE 13.—Acreage burned and size of fire by types and forest groups, 1911-1920, 
general-risk fires 
NORTHERN GROUP OF FORESTS 
w 
Total Size of | Area 
Type teens acreage ee C fires aver- burned 
burned age fire nually 
1,000 
acres Acres |Number|Number|Per cent| Acres |Per cent 
Wiesterniyellow pine@s2= = = a 1, 491 205, 026 1, 051 243 23.1 195 1.38 
IVaxed*coniten =e at see 2 toe eis ee 1, 328 78, 515 1, 037 231 22.3 76 . 59 
WO uplaS HiT S Si se es Sree aE ae es 1, 101 88, 958 602 176 29. 2 148 81 
SRT Se Ree a cree NEE eect ieee arte 341 6, 168 207 30 14.5 30 .18 
BYU ers Sk ee ae ooo rer 1,045 | 159, 981 639 196 30.7 251 5s 
EAST SIDE AND NORTHERN AND SOUTHERN SIERRA GROUPS 
Wiesternyellow: pinei= 22: 2 eee ete 3,063 | 190,721 | 2,039 399 19.6 94 0. 62 
Nixeds conifers ie wants ese A 1, 799 94,210 | 1, 487 290 20. 2 66 B52 
DDOUCTAS SiR eS 2) AES ee Oe 44 374 24 6 25.0 16 . 08 
SSL 3 tess ae a tecg eS SiN Seve Sep As 1, 303 15, 906 544 44 8.1 29 12 
HES TUIS Hee ete eye page Rs gee eel sh 1, 194 118, 026 461 187 40. 6 256 99 
CONCENTRATION OF HAZARD AREAS 
These losses in percentage of area burned, like occurrence of fires, 
are not uniformly distributed over the entire area of each type but 
are concentrated in well-defined zones. For the decade under review 
in many localities in the northern group of forests, over 40 per cent 
of all fires became class C, and the burned acreage was correspondingly 
high. The protection problem is particularly critical on such areas, 
and this is characteristic of the whole northern group of forests. In 
Table 14 are given the results of planimetering these areas of con- 
centration of high hazard on type and hazard maps of the Klamath, 
Trinity, Shasta, and California National Forests. Of the brush and 
chaparral area, 22.9 per cent had over 40 per cent C fires. This is 
the lowest degree of success in protection of any type. It is followed 
TABLE 14.—Concentration of hazard: Areas on which 40 per cent of C fires occurred 
in northern group of forests, 1911-1920 
Total . 
: Area with 40 per 
Types Tepe! cent C fires 
1,000 acres|1,000 acres| Per cent 
Mixed ‘conifer:and: westernsyellowapines = s=2 58) 2 os ee ee 2, 819 373 ae 
TD Yoyb etd YS ih ea gee Pig ne, ed eres edge UO onthe eb te es tage neal eee SSL Sw ee 1, 101 101 9.2 
Hirisuearpine=fir, and valipin ess ss see oe wre ee ON eee eee pele ea ee 671 63 9. 4 
Total timbered sates ees Dee eee a PN ees oe 4, 591 537 iW ar 
BTUSH CHAD ATE Ae scene ee ee aes eee een ee ae ee 1, 303 299 22.9 
Grass:swood Dam dite. sts fees het, er ee a oe oe es Cena eee 353 48 13.6 
Total montimbered st. 222222. 22h Se eee ee eee YES 58 Mais ©, S 1, 656 347 20.9 
A Gy PEs eae oe Ae 5 a ee ee eee 6, 247 884 14.1 
