Douglas fir

Appearance

Coast Douglas fir is currently the second-tallest conifer in the world . Extant coast Douglas fir trees 60–75 m or more in height and 1.5–2 m in diameter are common in old growth stands, and maximum heights of 100–120 m and diameters up to 4.5–6 m have been documented. The tallest living specimen is the "Doerner Fir", previously known as the Brummit Fir, 99.4 m tall, at East Fork Brummit Creek in Coos County, Oregon, the stoutest is the "Queets Fir", 4.85 m in diameter, in the Queets River valley of Olympic National Park in Washington. Douglas firs commonly live more than 500 years and occasionally more than 1,000 years.




The bark on young trees is thin, smooth, gray, and contains numerous resin blisters. On mature trees, it is thick and corky. The shoots are brown to olive-green, turning gray-brown with age, smooth, though not as smooth as fir shoots, and finely pubescent with short, dark hairs. The buds are a very distinctive, narrow, conic shape, 4–8 mm long, with red-brown bud scales. The leaves are spirally arranged, but slightly twisted at the base to lie flattish on either side of the shoot, needle-like, 2–3.5 cm long, green above with no stomata, and with two whitish stomatal bands below. Unlike the Rocky Mountain Douglas fir, coast Douglas fir foliage has a noticeable sweet fruity-resinous scent, particularly if crushed.

The mature female seed cones are pendent, 5–8 cm long, 2–3 cm broad when closed, opening to 4 cm broad. They are produced in spring, green at first, maturing orange-brown in the autumn 6–7 months later. The seeds are 5–6 mm long and 3–4 mm broad, with a 12–15-mm wing. The male cones are 2–3 cm long, dispersing yellow pollen in spring.

In forest conditions, old individuals typically have a narrow, cylindric crown beginning 20–40 m above a branch-free trunk. Self-pruning is generally slow and trees retain their lower limbs for a long period. Young, open-grown trees typically have branches down to near ground level. It often takes 70–80 years for the trunk to be clear to a height of 5 m and 100 years to be clear to a height of 10 m .

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% 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 to 88/g . Seeds from the northern portion of its range tend to be larger than seeds from the south.

Naming

The common name honors David Douglas, a Scottish botanist and collector who first reported the extraordinary nature and potential of the species. The common name is misleading since it is not a true fir, i.e., not a member of the genus ''Abies''. For this reason the name is often written as Douglas-fir .

The specific epithet, ''menziesii'', is after Archibald Menzies, a Scottish physician and rival naturalist to David Douglas. Menzies first documented the tree on Vancouver Island in 1791. Colloquially, the species is also known simply as Doug-fir or as Douglas pine .

Distribution

One variety, coast Douglas fir , grows in the coastal regions, from west-central British Columbia southward to central California. In Oregon and Washington, its range is continuous from the eastern edge of the Cascades west to the Pacific Coast Ranges and Pacific Ocean. In California, it is found in the Klamath and California Coast Ranges as far south as the Santa Lucia Range, with a small stand as far south as the Purisima Hills in Santa Barbara County. In the Sierra Nevada, it ranges as far south as the Yosemite region. It occurs from near sea level along the coast to 1,800 m above sea level in the California Mountains.

Further inland, coast Douglas fir is replaced by another variety, Rocky Mountain or interior Douglas fir . Interior Douglas fir intergrades with coast Douglas fir in the Cascades of northern Washington and southern British Columbia, and from there ranges northward to central British Columbia and southeastward to the Mexican border, becoming increasingly disjunct as latitude decreases and its altitudinal limits increase. Mexican Douglas fir , which ranges as far south as Oaxaca, is often considered part of ''P. menziesii''.

Habitat

The rooting habit of coast Douglas fir is not particularly deep, with the roots tending to be shallower than those of same-aged ponderosa pine, sugar pine, or California incense-cedar, though deeper than Sitka spruce. Some roots are commonly found in organic soil layers or near the mineral soil surface. However, Douglas fir exhibits considerable morphological plasticity, and on drier sites coast Douglas fir will generate deeper taproots. Interior Douglas fir exhibits even greater plasticity, occurring in stands of interior temperate rainforest in British Columbia, as well as at the edge of semi-arid sagebrush steppe throughout much of its range, where it generates even deeper taproots than coast Douglas fir is capable.


Douglas fir snags are abundant in forests older than 100–150 years and provide cavity-nesting habitat for numerous forest birds. Mature or "old-growth" Douglas fir forest 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 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 metres above the ground. The red vole's diet consists chiefly of Douglas fir needles. A parasitic plant sometimes utilizing ''P. menziesii'' is Douglas-fir dwarf mistletoe .

Its seedlings are not a preferred browse of black-tailed deer and elk , but can be an important food source for these animals during the winter when other preferred forages are lacking. In many areas, Douglas fir needles are a staple in the spring diet of blue grouse . In the winter, New World porcupines primarily eat the inner bark of young conifers, among which they prefer Douglas fir.

The leaves are also used by the woolly conifer aphid ''Adelges cooleyi''; this 0.5 mm long sap-sucking insect is conspicuous on the undersides of the leaves by the small white "fluff spots" of protective wax that it produces. It is often present in large numbers, and can cause the foliage to turn yellowish from the damage in causes. Exceptionally, trees may be partially defoliated by it, but the damage is rarely this severe. Among Lepidoptera, apart from some that feed on ''Pseudotsuga'' in general the gelechiid moths ''Chionodes abella'' and ''C. periculella'' as well as the cone scale-eating tortrix moth ''Cydia illutana'' have been recorded specifically on ''P. menziesii''.


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 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. The seeds are also important in the diets of several seed-eating birds. These include most importantly American sparrows  – dark-eyed junco , song sparrow , golden-crowned sparrow and white-crowned sparrow  – and true finches  – pine siskin , purple finch , and the Douglas fir red crossbill which is uniquely adapted to foraging for ''P. menziesii'' seeds.

The coast Douglas fir variety is the dominant tree west of the Cascade Mountains in the Pacific Northwest, occurring in nearly all forest types, competes well on most parent materials, aspects, and slopes. Adapted to a moist, mild climate, it grows larger and faster than Rocky Mountain Douglas fir. Associated trees include western hemlock, Sitka spruce, sugar pine, western white pine, ponderosa pine, grand fir, coast redwood, western redcedar, California incense-cedar, Lawson's cypress, tanoak, bigleaf maple and several others. Pure stands are also common, particularly north of the Umpqua River in Oregon.

Shrub associates in the central and northern part of coast Douglas fir's range include vine maple , salal , Pacific rhododendron , Oregon-grape , red huckleberry , and salmonberry . In the drier, southern portion of its range shrub associates include California hazel , oceanspray , creeping snowberry , western poison-oak , ceanothus , and manzanita . In wet coastal forests, nearly every surface of old-growth coast Douglas fir is covered by epiphytic mosses and lichens.

Poriol is a flavanone, a type of flavonoid, produced by ''P. menziesii'' in reaction to infection by ''Poria weirii''.

Uses

Douglas fir is one of the world's 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 treated pilings and decking are used in marine structures. The wood is also made into railroad ties, mine timbers, house logs, posts and poles, fencing, flooring, pulp, and furniture. 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.

This plant has ornamental value in large parks and gardens, and has gained the Royal Horticultural Society's Award of Garden Merit.

Away from its native area, it is also extensively used in forestry as a plantation tree for timber in Europe, New Zealand, Chile and elsewhere. It is also naturalised throughout Europe, Argentina and Chile , and in New Zealand sometimes to the extent of becoming an invasive species subject to control measures.

The buds have been used to flavor eau de vie, a clear, colorless fruit brandy.

Native Hawaiians built ''waʻ kaulua'' from coast Douglas fir logs that had drifted ashore.