The rugged relief of the far north creates a steep climatic gradient that confines the forest to a narrow coastal strip. Each zone supports distinct associations of dominant species. Sitka spruce and western and mountain hemlock dominate the subpolar zone. Sitka spruce, western red cedar, and western hemlock characterize the perhumid zone. Douglas-fir joins these species as a dominant in the seasonal zone.
Coast redwood distinguishes the redwood zone.
Map based on technical analysis by Andrew P. Mitchell, Randall H. Hagenstein, Lisa J. Lackey, and Marko Z. Muellner.