16 BULLETIN 1495, U. S. DEPARTMENT OF AGRICULTURE 
Up to June 11 the total number of fires is distinctly higher in the 
western yellow pine and mixed conifer types than in the other timber 
types, and this continues to be true during the remainder of June 
and July. In August, however, the rate per 100,000 acres in the 
Douglas fir, sugar pine-fir, and fir types approaches the average of 
25.56 for the combined pine types given in Figure 5. September is 
marked by a decided failing off in number of fires in all types, though 
the danger point is exceeded everywhere. 
In the first 10-day period of October, as the end of the fire season 
is approached, the number of fires in all types except grassland is 
still at or above the danger pomt. In the second 10-day period, 
however, the rate for fir and sugar pine-fir drops so low that the 
season in these types may be considered closed. The third 10-day 
period of October sees the woodland type down to a similar basis 
of an occasional! fire, but the western yellow pine, mixed conifer, 
Douglas fir, chaparral, and brush types must still be pretected. By 
November, only the chaparral type continues in the danger zone, 
and before the end of the month even this is down to a low figure. 
When these figures are summarized (Table 6 and fig. 5), the long- 
est fire season is found to be five and two-thirds months, in the 
chaparral and brush, and the shortest, four months, in the fir and 
sugar pine-fir types. The principal timber types—the western yel- 
low pine, mixed conifer, and Dcuglas fir—have a common season of 
five and one-third months. | 
The limitations of these figures should be clearly recognized. 
They do not mean that in each individual year for each national forest 
the actual fire season is of the indicated length. Their significance 
lies rather in what they show of the relationshtp between the types. 
For example, they show an average lag of three weeks in opening date 
between the western yellow pine and fir types, a fact that can be 
taken into account in placing special-protection men and in making 
allotments. They show that the fire season lasts three weeks longer 
in the pine types than in the fir and sugar pine-fir types, a fact that 
also can be reckoned on. ‘The actual opening and closing dates for 
a particular year may vary considerably from the dates given in Table 
6, depending principally upon the prevalence or absence of rain. 
TasBLE 6.—Average length of fire seasons by types 1 
Length | 
: : : : Length 
Opening | Closing Opening | Closing : 
Type Type in 
date date ER date date Tanithe 
Western yellow pine_| May 20 | Oct. 31 5i4all Grasses s pees eee June 10} Oct. 20 414 
Mixed conifer_________ Peo (oye ee eS Gos se 54 | Chaparraléss 222) 2s May 20 | Nov. 10 524 
Douglas fir es ETc Koya eee | a dof 544 Woodlands: 22 222 June 10] Oct. 20 414 
Sugar pine-fir________ June 10 {| Oct. 10 4 Brushe se sess Swe ee May 10] Oct. 31 5% 
Riiremep iss ic anaes aide 2 [ee dos: | 4 
1 Basis: Occurrence of fires at rate exceeding one fire to 100,000 acres per 10 days, 12 timbered forests. 
A point of considerable significance is that the opening date is the 
same for all the timber types comprising the bulk of the forest areas— 
western yellow pine, mixed conifer, and Douglas fir. To provide 
protection only for the western yellow pine type, as has sometimes 
been done, thus appears to be an unsound practice, overlooking the 
possibility of danger to the other types, 
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