Historic fires in the central western Cascades, Oregon

The history of fire between 1850 and 1977 in a portion of theWillamette National Forest in the central Western Cascades of Oregon wasdocumented using historical sources. Three types of records wereavailable: (1) records and writings not primarily concerned with firebut yielding information about fire in context with human activities,(2) descriptive accounts of fires prior to 1910, and (3) statisticalreports generated by the U.S. Forest Service from 1910 to the present.Corresponding to each type of record, this study was divided into threetime periods: pre-1850, 1850-1909, and 1910-1977.
Information about the pre-1850 period was drawn from reconstruc-tions of aboriginal forest use by anthropologists, archaeologists, andenthnographers. Although four groups of aboriginal people inhabitedareas within or adjacent to the study area, evidence is lacking forintentional Indian burning in the central Western Cascades. Unintentional burning from untended or abandoned campfires is probable.Coupled with naturally occurring lightning-caused fires, these fires were ample ignition to maintain an age class of 125 years or older inthe forests of the central Western Cascades.
Information about fires occurring between 1350 and 1909 came from avariety of historic sources. All chronicled fires were attributed to man. Many man-caused fires were related to specific human activities,including road building, sheep grazing, and camping. As human use increased, the numbers of fires increased. Conflicts in use occurredbecause of the threat of fire. Some activities, such as mining andrailroading, were not causes of fire in the central Western Cascades.Lightning was not regarded as a cause of forest fires until after 1900.
Fire records for the period from 1910 to 1977 were generated by theU.S. Forest Service. These records exist in various forms includingfire maps, summary tables, and individual fire reports. Almost 60percent of all recorded fires from 1910 to 1977 were lightning caused. While lightning ignited more fires, they were usually small and occurredin mid-summer. Man-caused fires although fewer, were larger and occurredthroughout the fire season. An increase in the number of fires is paralleled by an increase in forest use.
Two maps were constructed to illustrate the spatial distribution ofman-caused and lightning-caused fires. Lightning-caused fires appear tobe unevenly distributed over the landscape. Three areas exhibit a lowincidence of lightning-caused fires. Lightning fires occur at higherelevations, where fuel accumulations are less, and tend to remain small.Man-caused fires exhibit a definite pattern corresponding with land-use.These fires tend to follow major transportation routes which are generally at lower elevations. Man-caused fires, ignited at lower elevations,have more chance to spread and become large fires.