From Wikipedia, the free encyclopedia.
Pseudotsuga menziesii var. menziesii is the botanical name for the Coast variety of the Douglas-fir.
Coast Douglas-fir grows from west-central British Columbia southward to central California. In Oregon and Washington its range is continuous from the Cascades west to the Pacific Ocean. It is the most dominant tree species in the Pacific Northwest, occurring in nearly all forest series, from near sea level along the coast to above 1,500 m (5,000 feet) in the Cascades. It competes well on most parent materials, aspects, and slopes. Pure stands are common north of the Umpqua River in Oregon. In California, it is found in the Klamath and Coast ranges as far south as the Santa Cruz Mountains, and in the Sierra Nevada as far south as the Yosemite region.
Coast Douglas-fir is a large, coniferous, evergreen tree. Adapted to a moist, mild climate, it grows bigger and more rapidly than the inland variety. Trees 75 m (250 feet) or more in height and 150-180 cm (5-6 feet) in diameter are common in old-growth stands. These trees commonly live more than 500 years and occasionally more than 1,000 years. Old individuals typically have a narrow, cylindric crown beginning 20-40 m (65-130 feet) above a branch-free bole. Self-pruning is generally slow and trees retain their lower limbs for a long period. Young, open-grown trees typically have branches near the ground. It often takes 70-80 years for the bole to be clear to a height of 5 m (17 feet) and 100 years to be clear to a height of 10 m (33 feet). In wet coastal forests, nearly every surface of old-growth coast Douglas-fir is covered by epiphytic mosses and lichens.
This tree's rooting habit is not particularly deep. The roots of young coast Douglas-fir tend to be shallower than roots of the same aged ponderosa pine, sugar pine, or incense-cedar. Some roots are commonly found in organic soil layers or near the mineral soil surface. The bark on young individuals is thin, smooth, gray, and contains numerous resin blisters. On mature trees the bark is thick (10-30 cm / 4-12 inches) and corky. Foliage consists of yellowish-green, 2.5 cm (1 inch) long needles spirally arranged around the branchlets. Pendent, 5-10 cm (2-4 inches) long cones are located primarily in the upper crown.
Appreciable seed production begins at 20-30 years in open-grown coast Douglas-fir. Seed production is irregular; over a 5-7 year period, stands usually produce one heavy crop, a few light or medium crops, and one crop failure. Even during heavy seed crop years, only about 25 percent of trees in closed stands produce an appreciable number of cones. Each cone contains around 25 to 50 seeds. Seed size varies; average number of cleaned seeds varies from 70,000-88,000/kg (32,000-40,000 per pound). Seeds from the northern portion of coast Douglas-fir's range tend to be larger than seed from the south.
Shrub associates in the central and northern part of coast Douglas-fir's range include vine maple (Acer circinatum), salal (Gaultheria spp.), Pacific rhododendron (Rhododendron macrophyllum), Oregon grape (Mahonia aquifolium), red huckleberry (Vaccinium parvifolium), and salmonberry (Rubus spectabilis). In the drier, southern portion of its range shrub associates include California hazel (Corylus cornuta var. californica), oceanspray (Holodiscus discolor), creeping snowberry (Symphoricarpos mollis), western poison-oak (Toxicodendron diversilobum), ceanothus (Ceanothus spp.), and manzanita (Arctospaphylos spp.).
Coast Douglas-fir is one of the worlds best timber producers and yields more timber than any other tree in North America. The wood is used for dimensional lumber, timbers, pilings, and plywood. Creosote-soaked pilings and decking are used in marine structures. The wood is also made into railroad ties, mine timbers, house logs, posts and poles, flooring, veneer, pulp, and furniture. Coast Douglas-fir is used extensively in landscaping. It is planted as a specimen tree or in mass screenings. It is also a popular Christmas tree.
Coast Douglas-fir seedlings are not a preferred browse of black-tailed deer or wapiti, but can be an important food source for these animals during the winter when other preferred forages are lacking. Douglas-fir seeds are an extremely important food for small mammals. Mice, voles, shrews, and chipmunks consumed an estimated 65 percent of a Douglas-fir seed crop following dispersal in western Oregon. The seeds are also important in the diets of the Pine Siskin, Song Sparrow, Golden-crowned Sparrow, White-crowned Sparrow, Red Crossbill, Dark-eyed Junco, and Purple Finch.
The Douglas squirrel harvests and caches great quantities of Douglas-fir cones for later use. They also eat mature pollen cones, developing inner bark, terminal shoots, and tender young needles.
Mature or "old-growth" coast Douglas-fir is the primary habitat of the Red tree vole and the Spotted Owl. Home range requirements for breeding pairs of spotted owls are at least 400 ha (1,000 acres) of old-growth. Red tree voles may also be found in immature forests if Douglas-fir is a significant component. This animal nests almost exclusively in the foliage of Douglas-fir trees. Nests are located 2-50 m (6-160 feet) above the ground. The red vole's diet consists chiefly of coast Douglas-fir needles.
In many areas coast Douglas-fir needles are a staple in the spring diet of Blue Grouse. In the winter, porcupines primarily eat the inner bark of young conifers, especially Douglas-fir. Douglas-fir snags are abundant in forests older than 100-150 years and provide cavity-nesting habitat for numerous forest birds.