The rain forests are just one type of forest found in the Olympic Mountains. Franklin and Dyrness set out 5 forest zones: Sitka spruce, western hemlock, silver fir, mountain hemlock, and subalpine parkland. Other authors include a sixth, Douglas-fir zone. Different plant associations are typical of one or more forest zones. For instance, the rain forest plant association described above is a member of the Sitka spruce forest zone.