Landscape patterns of pre-logging forest conditions in western Oregon

Using historical maps and tools provided by GIS, the spatial patterns ofpre-logging forest conditions were quantified for three landscapes in westernOregon. The spatial coincidence between forest patches and topographicfeatures was determined for slope gradient, aspect, elevation, and distancefrom streams. Pre-logging and current forest compositions were compared.
The pre-logging landscape was dominated by old growth conifer withless than 10% consisting of early seral disturbance patches. Fire patchesdiffered in size and shape between the Oregon Coast Range and the OregonCascade Range provinces. The size and variability of fire patches was larger inthe Cascades, with shorter mean distances between fire patches and smallerperimeter to area ratios compared to fire patches in the Coast Range. Meanfire return intervals ranged from 170 to 292 years for the Oregon Coast Range.The most frequent patch size, regardless of patch type and study area, rangedfrom 100 to 999 ha. Forest patch types varied predictably by topographicfeature for instance: fewer fire patches occurred on cool, moist aspects whilemore occurred on hot, dry, aspects. More burn area and less old growthconifer than expected occurred within 4000 m of major rivers. Late seralforest cover has declined dramatically across all three landscapes since 1933.