United States Department of Agriculture

Characteristics of Remnant Old-growth Forests in the Northern Coast Range of Oregon and Comparison to Surrounding Landscapes United States Department of Agriculture

Publisher Marketing: Old-growth forests provide unique habitat features and landscape functions compared to younger stands. The goals of many forest management plans in the Pacific Northwest include increasing the area of late-successional and old-growth forests. The goal of this study was to describe existing old-growth forests in the northern Oregon Coast Range that might serve as examples of desired future conditions and developmental pathways. In addition, the abundance of specific stand attributes associated with old-growth stands was estimated from regional inventory data. Most of the old-growth stands had experienced moderately severe disturbances during their development resulting in mid- and understory trees belonging to cohorts younger than those of overstory trees. Most of the stands had the full complement of old-growth attributes (large shade-intolerant trees, shadetolerant trees, snags, and down wood), although the dead wood attributes tended to be less abundant in drier stand types. Thresholds for at least four of the five old-growth attributes were met on 7 percent of the inventory plots on federal lands, but on only 0.4 percent of the inventory plots on nonfederal lands. Shade-intolerant trees in particular were low in abundance in mature stands of intermediate diameter class (10 to 30 in). Large-diameter class stands (>30 in) were more abundant near the coast than near the Willamette Valley margin. Results suggest that although old-growth forests can develop along multiple pathways, stand composition and productivity constrain development such that expecting all late-successional stands to have the full complement of old-growth attributes may not be realistic.