Fire Episodes in the Inland Northwest (1540-1940) Based on Fire History Data
USDA Forest Service, Intermountain Research Station, General Technical Report INT-GTR-370, 17 pp.
Information from fire history studies in the northwestern United States was used to identify and map "fire episodes" (5 year periods) when fire records were most abundant. Episodes of widespread landscape-scale fires occurred at average intervals of 12 years. Mean annual acreage burned was calculated based on estimated areas of historical vegetation types with their associated fire intervals from the fire history studies. An average of about 6 million acres of forest and grass and shrubland burned annually within the 200 million acre Columbia River Basin study region, and especially active fire years probably burned twice this much area. For comparison, the largest known fire years since 1900 have each burned 2 million to 3 million acres in this region. We also compare the occurrence of regional fire episodes to drought cycles defined by tree-ring studies.
Barrett, Stephen W.; Arno, Stephen F.; and Menakis, James P., "Fire Episodes in the Inland Northwest (1540-1940) Based on Fire History Data" (1997). The Bark Beetles, Fuels, and Fire Bibliography. Paper 43.