of the season the greatest percentage of the fires 

 caused by man is Class A. Fifty-seven percent of 

 the fires occur in May and June — a month 

 earlier than for lightning fires; land-clearing op- 

 erations are a major reason for this early peak- 

 load. Only a few fires occur in October and 

 November, but a larger percentage of them 

 reaches Class E size because the entire detection 

 and control force has been drastically reduced 

 by this time. 



Acreage burned. — The record of actual acre- 

 age burned in each month (fig. 55) shows clearly 

 that the small number of Class E fires during 

 May, June, and July accounts for most of the 

 total amount. Seventy-three percent of all acre- 

 age burned by lightning fires occurs in June. 

 Seventy percent of all acreage burned by man- 

 caused fires occurs in May. Lightning fires con- 

 tinue to burn much larger acreages in July than 

 do man-caused fires; in fact, July lightning fires 

 burn almost the same acreage as man-caused 

 fires do in May. 



Yearly Variation in Fire Frequency and Size 



For the 9-season period studied, the gener- 

 alization could be made that as the total number 

 of fires increased, the number of Class E fires 

 also increased, and the number of Class A fires 

 decreased. This relationship is partly due to 

 overloading of the fire control organization and 

 partly due to many fires reaching such large size 

 that no effective suppression action could be 

 taken. The percentage of the Class B, C, and D 

 fires does not vary greatly from year to year; 

 the main difference in percentage is between 

 Class A and Class E fires (fig. 56). The area- 

 burned-per-fire record for 1957 — the worst year 

 — and 1955 — the easiest year (fig. 46) — falls 

 within this number-size class relationship. 



Distribution of Fires 



Fire control strategy cannot be planned 

 properly without first knowing where and when 

 fires are most likely to occur. Bases must be 

 established and personnel deployed and shifted 

 according to this knowledge. Data from the anal- 



ysis of fires from 1950 through 1958 were insuf- 

 ficient to make detailed occurrence isograms for 

 individual years or for separate size classes; 

 however, figures 57 and 58 show the number of 

 man-caused fires and lightning fires per million 

 acres for this period. 



Most man-caused fires burn near population 

 centers and along the primary highways connect- 

 ing these principal cities (fig. 57). Exceptions to 

 this general rule are such towns as Tanana and 

 Fort Yukon. No roads go near these towns, but 

 in Alaska they are still centers of population or 

 distribution points. 



Distribution of lightning fires (fig. 58) ap- 

 pears somewhat similar to that for man-caused 

 fires in respect to their apparent concentrations 

 near the larger towns and along the primary 

 highways — particularly around Fairbanks, Tana- 

 cross, and the connecting road. Other apparent 

 centers of lightning fire frequency are near Kot- 

 zebue, Galena, McGrath, and between Eagle 

 and Central along the Canadian border. The 

 scatter of fires was so great that this table at 

 best could show only an approximation. 



If complete detection coverage were pos- 

 sible, the lightning fire isogram might appear 

 considerably different. Over the past many 

 years, detection and reporting have been almost 

 entirely by such volunteers as airplane pilots, 

 travelers, local residents, and miners. We now 

 know that many lightning fires occur in areas 

 for which the isogram indicates a low frequency. 

 Some of these fires burn large areas, and some 

 may combine with other fires and appear as 

 only one for reporting purposes. Others burn 

 and die out without being reported. Many fires 

 do not spread beyond a very small size, and 

 their existence is never known. Better detection 

 and better reporting methods will no doubt 

 change the pattern of the lightning fire isogram 

 during the next few years. More information 

 pertaining to fire distribution according to size 

 class and distance from headquarters appears 

 in chapter 8. 



65 



