Retrospective analysis of forest landscape patterns in western Oregon

Using historical vegetation maps from the 1930s and a geographic infor-mation system, we quantified the spatial patterns of prelogging forest conditions inwestern Oregon. Specifically, we measured the composition and spatial distribution offorest patches and determined fire patch characteristics for three landscape study areas.The spatial coincidence between forest patches and topographic features was evaluatedfor slope gradient, aspect, elevation, and distance from streams. The prelogging land-scapes of western Oregon were dominated by old-growth conifer with lesser amounts ofmid- and early seral forest. Fire patches differed in size and shape between the OregonCoast Range and the Oregon Cascades Range physiographic provinces. Fire patch sizeand variability were greater in the Cascades Range, with shorter mean distances betweenfire patches and smaller perimeter-to-area ratios compared to fire patches in the CoastRange. Forest patch types varied predictably by topographic feature. For instance, fewerfire patches occurred on cool, moist aspects, while more occurred on hot, dry, aspects.More burn area and less old-growth conifer than expected occurred within 4,000 m ofmajor rivers. Assessing historical forest landscape patterns is useful for understandingdisturbance regimes and the ecosystem processes that are associated with them.
Index terms: fire disturbance, historical forest conditions, landscape patterns, westernOregon