At its southern extent, the zone narrows again, confined to the fog belt not by mountains but by moisture. 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.
The coast redwood zone was also mapped, based on a data layer of vegetation cover types of California. The resulting data layer, combined with the coastal western hemlock biogeoclimatic zone data for British Columbia and the redwood zone for California, represents the probable pre-European settlement distribution of coastal temperate rain forest. They have been heavily harvested, particularly in the southern third of the bioregion. In Map 8, mature coastal forests that have not been extensively logged or disturbed by other development appear green. Other areas within the bioregion, shown in gold, consist of undis turbed bog, muskeg, and high-elevation rain forest.