Western white pine is represented in 18 forest cover types of western North America and Canada. It is the key species in Western White Pine (Society of American Foresters Type 215) (9). In this type, western white pine constitutes a plurality of stocking, but many other species such as grand fir (Abies grandis), subalpine fir (A. lasiocarpa), California red fir (A. magnifica), lodgepole pine (Pinus contorta), ponderosa pine (P. ponderosa), western larch (Larix occidentalis), western redcedar (Thuja plicata), western hemlock (Tsuga heterophylla), Douglas-fir (Pseudotsuga menziesii), Engelmann spruce (Picea engelmannii), and mountain hemlock (Tsuga mertensiana) may also be present. Most often the western white pine component of Type 215 is even aged with an understory containing multi-aged trees of the more shade-tolerant species such as western hemlock and western redcedar. Occasionally, light overstory components of more intolerant species, such as western larch and lodgepole pine, may also be present.
In the 17 other cover types, western white pine is a common component, along with many other species, including Pacific silver fir (Abies amabilis), white fir (A. concolor), noble fir (A. procera), Port-Orford-cedar (Chamaecyparis lawsoniana), incense-cedar (Libocedrus decurrens), Sitka spruce (Picea sitchensis), whitebark pine (Pinus albicaulis), foxtail pine (P. balfouriana), limber pine (P. flexilis), sugar pine (P. lambertiana), Jeffrey pine (P. jeffreyi), Pacific yew (Taxus brevifolia), Pacific madrone (Arbutus menziesii), bigleaf maple (Acer macrophyllum), red alder (Alnus rubra), quaking aspen (Populus tremuloides), and paper birch (Betula papyrifera). These cover types are as follows:
205 Mountain Hemlock
206 Engelmann Spruce-Subalpine Fir
207 Red Fir
210 Interior Douglas-Fir
212 Western Larch
213 Grand Fir
218 Lodgepole Pine
224 Western Hemlock
226 Coastal True Fir-Hemlock
227 Western Redcedar-Western Hemlock
228 Western Redcedar
229 Pacific Douglas-Fir
230 Douglas-Fir-Western Hemlock
231 Port-Orford-Cedar
237 Interior Ponderosa Pine
247 Jeffrey Pine
256 California Mixed Subalpine
In northern Idaho and eastern Washington, the most important habitat types in which western white pine grows are Tsuga heterophylla / Clintonia uniflora, Thuja plicata / Clintonia uniflora, and Abies grandis / Clintonia uniflora (6). Western white pine is a major seral species in the Tsuga heterophylla / Clintonia uniflora habitat type in western Montana and is also present in several others (21). Western white pine is present in several vegetative associations, communities, and zones in western Oregon and Washington but is a major constituent only of the Tsuga heterophylla zone in the Puget Sound area of Washington (5,11,14).
Most of the habitat types, associations, and communities in Washington, Oregon, and the Inland Empire where western white pine grows are strikingly rich in other woody and herbaceous flora (5,6,11,14,21). In contrast, in the Sierra Nevada the vegetation associated with western white pine is characteristically sparse. Shrubs associated with western white pine include huckleberry (Vaccinium spp.), willow (Salix spp.), honeysuckle (Lonicera spp.), wintergreen (Gaultheria spp.), azalea (Rhododendron spp.), prickly currant (Ribes lacustre), sticky currant (R. viscosissimum), Rocky Mountain maple (Acer glabrum), Greenes mountain-ash (Sorbus scopulina), princes-pine (Chimaphila umbellata), snowberry (Symphoricarpos albus), whipplea (Whipplea modesta), ocean-spray (Holodiscus discolor), serviceberry (Amelanchier alnifolia), ninebark (Physocarpus malvaceus), rustyleaf menziesia (Menziesia ferruginea), spirea (Spiraea betulifolia), pachistima (Pachistima myrsinites), and twinflower (Linnaea borealis). Graminoids frequently associated with western white pine include sedge (Carex spp.), woodrush (Luzula spp.), Columbia brome (Bromus vulgaris), pine grass (Calamagrostis rubescens), and nodding trisetum (Trisetum cernuum). Forbs found growing with western white pine include false solomons-seal (Smilacina spp.), twistedstalk (Streptopus spp.), coolwort (Tiarella spp.), violet (Viola spp.), wild ginger (Asarum caudatum), queenscup (Clintonia uniflora), western goldthread (Coptis occidentalis), bunchberry (Cornus canadensis), sweetscented bedstraw (Galium triflorum), white trillium (Trillium ovatum), and Brewers lupine (Lupinus breweri).