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Abstract

Fire History of Pseudotsuga menziesii and Abies grandis Stands in the Blue Mountains of Oregon and Washington
by K. Maruoka (University of Washington)

Fifteen sites in the Blue Mountains of Oregon and Washington were sampled to survey fire frequency in stands ranging from Pseudotsuga menziesii associations to dry Abies grandis associations. Current stand structure at 80% of the sites consists of an overstory dominated by ponderosa pine, with Douglas-fir and grand fir the understory dominants. Pulses of establishment of Douglas-fir and grand fir occurred after the last recorded fire at 53% of the sites, while establishment pulses occurred amidst years of recorded fires at 47% of the sites. Patchiness in fire severity and fire spread, variable regeneration patterns, and sampling design may have influenced the interpretation of current stand structure in the context of fire. Fire scar analyses reveal high variability in fire return intervals. Mean fire return intervals at each site range from 9.9 years to 49.0 years. Individual fire return intervals range from 2 years to 119 years, but may be highly subject to sampling limitations. Fire frequency variability could not be linked between sites to physical or geographic gradients.