Trees and Shrubs. William Clark's journal sketch of Salal Lewis & Clark Journals. The Sitka spruce vegetation zone forms a narrow band along the northwest coast from northern California to southeastern Alaska. The mild, wet maritime climate and rich soils create ideal growth conditions for conifers, resulting in climax spruce-hemlock forests of magnificent size and lush biodiversity. Sitka spruce (Picea sitchensis) is the dominant conifer in the park's forests. Western hemlock (Tsuga heterophylla), western redcedar (Thuja plicata), Douglas fir (Pseudotsuga menziesii), red alder (Alnus rubra), cascara (Rhamnus frangula), red elderberry (Sambucus racemosa) and several willow species are the common subdominant trees. Salal (Gaultheria shallon), huckleberries (Vaccinium spp), seven fern species, and a large number of mosses, liverworts, and lichens share the forest understory.