Forest fire history of Desolation Peak, Washington

Abstract

Forests in the vicinity of Desolation Peak, Washington, are of special ecological interest because of their transitional nature between coastal and interior forest types. The area is west of the Cascade Mountain crest but in the rainshadow of mountains farther to the west. Fire return intervals were hypothesized to be shorter than typical for coastal forest types, such as those dominated by western hemlock and Pacific silver fir, and longer than typical for interior forest types, such as ponderosa pine, owing to the close juxtaposition of these types at Desolation Peak. Seven forest community types were defined, and a 400-year fire history was developed for this 3500-ha area. The average natural fire rotation was 100 years; this varied by a factor of two by century and by topographic aspect. Forest types typical of coastal regions, such as Douglas-fir, – western hemlock and mountain hemlock – Pacific silver fir, had mean fire return intervals (108–137 years) much lower than in other western Washington areas. The most interior forest type, ponderosa pine – Douglas-fir, had a higher mean fire return interval (52 years) than reported for similar forest types east of the Cascades. Historically, fire has created structural and landscape diversity on Desolation Peak and may be an important process in the maintenance of such diversity into the future.