Forests

Douglas-fir

The Douglas-fir (scientific name: Pseudotsuga) is a genus of tree that includes ar least five species found in North America and Asia:

caption Douglas-fir. Yosemite National Park (Mariposa County, California, US) Photographer: Charles Webber

Scientific Classification

Kingdom: Plantae
Phylum:--- Tracheophyta
Class:------ Pinopsida
Order:-------- Pinales
Family:-------- Pinaceae
Genus:--------- Pseudotsuga

caption Japanese Douglas-fir. source: Wikipedia.
caption Cone of Coast Douglas-fir. Source: Peter Stevens/Wikimedia commons
caption Coast Douglas-fir. Source: Walter Siegmund/Wikimedia Commons
caption Japanese douglas-fir. Source: Wikimedia Commons
  • Bigcone Douglas-fir (Pseudotsuga macrocarpa)

  • Coast Douglas-fir (Pseudotsuga menziesii)
    --
    Pseudotsuga menziesii subsp. menziesii – regular Coast Douglas-fir
    -- Pseudotsuga menziesii subsp. glauca – Rocky Mountain Douglas-fir

  • Mexican Douglas-fir (Pseudotsuga lindleyana; included by some within Pseudotsuga menziesii subsp. glauca)

  • Chinese Douglas-fir (Pseudotsuga sinensis)
    --
    Pseudotsuga sinensis var. sinensis – regular Chinese Douglas-fir
    -- Pseudotsuga sinensis var. brevifolia – Short-leaf Chinese Douglas-fir (considered by some to be a separtae species)
    -- Pseudotsuga sinensis
    var. forrestii – Yunnan Douglas-fir (considered by some to be a separate species Pseudotsuga forrestii)
    -- Pseudotsuga sinensis var. gaussenii – Narrow-cone Chinese Douglas-fir
    -- Pseudotsuga sinensis var. wilsoniana – Taiwan Douglas-fir (considered by some to be a separate species Pseudotsuga wilsoniana)

  • Japanese Douglas-fir (Pseudotsuga japonica)

The Douglas-fir is evergreen (has leaves in all seasons) and a conifer (a cone-bearing seed plant that includes such trees as pines, spruces, and firs) with needle-like leaves. The Douglas-fir is a gymnosperm, but is not classified as a true fir taxon, which appellation is reserved for genus Abies.

Possibly the tallest recorded land plant of any species might have been a specimen of P. mensziesii, claimed as 126.5 meters tall, in Lynn Valley at Vancouver, British Columbia, Canada, which tree is no longer living; another specimen of the same species, claimed as a height of 120.0 meters, was recorded in Mineral, Washington. However, neither claim is verified, and (like many old tree measurements) are unlikely to be accurate. The tallest currently known is 99 meters tall.

The conservation status of both Asian species is classified by the IUCN as Vulnerable, chiefly from overharvesting due to high population densities and demand for wood, especially in China. Not only are the North American species considered non-threatened species, but P. menziesii is considered an aggressive species in part of its range, especially in California, where aggressive fire suppression has placed this conifer in a niche that it can out-compete oak species, in locations which are historically oak-dominant woodlands.

The North American members of the genus are strongly associated with the celebration of Christmas, using the tree itself as a major decoration, as well as use of boughs for accent decoration and wreath-making.

Physical Description

The genus level characteristics of this plant taxon include the fact that young trees have conic crowns, with branches appearing branches manifested as whorled. Bark of young individuals is typically smooth with resin blisters, while mature bark exhibits a thick, deeply furrowed, dark brown appearance. Leaf scars are more or less smooth and round, slightly raised above the twig surface on persistent leaf bases. Buds are generally less than fifteen millimeters in length and are fusiform. Young trees often exhibit drooping limber branch architecture.

Leaves are needle-like and are typically persistent for less than eight years. These needles are generally 2.0 to 4.5 centimeters, tapered to a short petiole above a persistent base, generally spreading and flat, with two whitish bands on the lower leaf surface.

Seed cones are drooping, hanging, or suspended from a point of attachment above. These cones are typically pendant, four to twenty cm long, and maturing within the first season; these cones may be persistent or deciduous, and exhibit a stalk less than two cm. Bracts have a more or less exserted form, and are three-toothed or lobed at the tip, without scales. Seeds (including the wings) are normally less than 25 millimeters in size.

Bigcone Douglas-fir

These trees typically grow to 25 meters tall and the trunk to 1.3 meters diameter at breast height (d.b.h).

The bark is reddish brown, aging dark blackish gray, scaly, and longitudinally fissured.

Branchlets are pendulous, reddish brown or pale brown, aging gray-brown, slender, flexible, and slightly pubescent.

Winter buds are reddish brown, ovoid-conical or fusiform-conical, and acute.

Leaves are 2.5-4 cm × ca. 2 mm, with two stomatal bands, abaxial, grayish white, base strongly twisted, apex acute.

Seed cones are greenish yellow when immature, ripening to dull brown, ovoid-cylindric, and 9-18 × 4-6 cm in size.

Seed scales at middle of cones are broadly cuneate-flabellate, thick, transversely convex, and 2-2.5 × 3-3.5 cm in size, often resinous, puberulent when young, soon glabrous, and faintly striate abaxially.

Bracts are exserted (protrude), not reflexed, and lingulate (shaped like a tongue), with the cusp longer than lateral lobes.

Seeds are brown, ovoid-conical, 1-1.2 cm × ca. 6 mm in size; the wing pale brown, obovate, and 1-1.4 cm in size.

Coast Douglas-fir

These trees typically grow to 100 meters tall and the trunk to 4 meters diameter at breast height (d.b.h.) in native range. The Rocky Mountain subspecies is smaller, rarely over 40 meters tall and 1.5 meters diameter.

The bark is dark gray-brown or blackish green, smooth, with resin blisters, aging rough and scaly with deep longitudinal fissures.

Branchlets are initially light yellow, becoming red-brown when dry, slightly pubescent.

Leaves are dark green adaxially in the Coast subspecies, glaucous in the Rocky Mountain subspecies; they are linear, 1.5-3.0 cm × 1-2 mm in size, and have two stomatal bands, abaxial, gray-white, apex obtuse or acuminate.

Seed cones are brown, glossy, ellipsoid-ovoid, and 5-11 × 3-4 cm in size; the Rocky Mountain subspecies has smaller cones, 4-7 cm long.

Seed scales are approximately rhombic, 2-2.5 × 2-2.5 cm in size, as long as or longer than wide.

Bracts are exserted, longer than seed scales, cusp straight or reflexed, 6-10 mm in size, tapering at apex, with lateral lobes, denticulate at margin.

Mexican Douglas-fir

This tree is similar in form to the Rocky Mountain Douglas-fir, but is genetically distinct. It is a smaller tree, 25-35 meters tall, with leaves green adaxially and with two dull grayish stomatal bands abaxially.

Chinese Douglas-fir

These trees grow to 50 meters tall and the trunk to 1 meters diameter at breast height (d.b.h).

The bark is gray or dark gray, irregularly and thickly scaly.

Branchlets are initially pale yellow or yellowish gray, aging gray, usually glabrous or slightly pubescent on main branchlets and densely pubescent on lateral branchlets.

Leaves are pectinately arranged (like the teeth of a comb ), linear and  typically 2-2.5 cm × about 2 mm in size, with abaxial stomatal bands, whitish or gray-green, base broadly cuneate, and apex emarginate.

Seed cones are pale purple, glaucous, maturing purplish brown, ovoid to ellipsoid- or conical-ovoid, and 3.5-8 × 2-4.5 cm in size.

Seed scales at the middle of the cones semiorbicular, flabellate, or reniform, 2.5-3 × 3.2-4.5 (-5) cm, rusty brown pubescent abaxially, base broadly cuneate or almost truncate, concave at sides.

Bracts are reflexed, cusp narrowly triangular, about 3 mm in size, and apex obtuse.

Seeds are irregularly brown spotted abaxially, triangular-ovoid, slightly depressed, densely rusty brown pubescent adaxially; and, wing obliquely ovate or semitrullate.

Pollination occurs in April, with seed maturity October-November.

Range

Bigcone Douglas-fir (Pseudotsuga macrocarpa)

United States - California, at 200-2400 m elevation. Habitat slopes, cliffs, and canyons, in chaparral and mixed conifer forests. The northernmost stands of the species, in Kern County, are about 35 kilometers east of the closest approach of Coast Douglas-fir. USDA hardiness zone 8.

It is a common species in the Coulter pine-Hardwood phase of California mixed conifer forests, typically found on steep north-facing slopes and in ravines, i.e., sites with relatively low fire frequency. At the lowest elevations (c. 1100 m) it occurs as scattered individuals 15-30 m tall above a closed canopy of Canyon Live Oak. At higher elevations (c. 1500 m) it becomes much more abundant (80-190 trees/ha) in a mixed Douglas-fir - oak canopy. Although often codominant with Bigcone Pine and Canyon Live Oak, it is typically found on relatively more mesic sites with lower fire frequency. Not surprisingly, then, it is also found in riparian habitats as a codominant with mesic hardwood species such as Bigleaf Maple and Western balsam poplar.

Coast Douglas-fir (Pseudotsuga menziesii)

Canada - British Columbia and Alberta

United States - Washington, Oregon, California, Idaho, Montana, Wyoming, Nevada, Utah, Colorado, Arizona, New Mexico, and Texas.

The coastal subspecies menziesii occurs from central British Columbia south along the Pacific Coast for about 2,200 km to latitude 34° 44'. USDA hardiness zone 7. The interior subspecies glauca (Rocky Mountain Douglas-fir) is found along the Rocky Mountains from British Columbia to northern Mexico, where it merges in an as-yet undetermined area into the closely related species of Mexican Douglas-fir. USDA hardiness zone 4.

Mexican Douglas-fir (Pseudotsuga lindleyana)

Mexico - Sierra Madre Occidental, Sierra Madre Oriental, and rare in the Sierra Madre del Sur, south to Oaxaca, where two small populations were recently discovered on Peña Prieta in the San Felipe Mts just north of Oaxaca City, and on Cerro Quiexobra 110 km SE of Oaxaca City, this at 16°22'N, the southernmost locality for the whole genus. The type locality is near Pachuca, Hidalgo, about 80 km NE of Mexico City.

Usually on north-facing slopes or high valleys, at 2300-3300 m, in moist conifer or mixed forests with high summer rainfall and dry winters. USDA hardiness zone 8.

Japanese Douglas-fir (Pseudotsuga japonica) Japan - Honshu (Kii Peninsula) and Shikoku (Kochi Prefecture) In temperate forests at 500-1100 m elevation

Chinese Douglas-fir (Pseudotsuga sinensis)

China - south Anhui, north Fujian, north Guizhou, west Hubei, northwest Hunan, northeast Jiangxi, south Shaanxi, SE Sichuan, central and northeast Yunnan, and Zhejiang all var. sinensis. Found at elevations of 600-2800(-3300) m in China, usually in evergreen broadleaf forests

Taiwan (var. wilsoniana). In Taiwan, var. wilsoniana is scarce, scattered in the island at altitudes of 800-2500 m, usually mixing with other trees . It is reported at 1400 to 2500 m in (a) broadleaf forest, (b) mixed Hemlock, Cypress, Pine and Fagaceae forest; and (c) exposed rocky slopes.

A substantial subpopulation is protected in Lin'an County, Zhejiang, China.

Pseudotsuga brevifolia - Guizhou and southwest Guangxi, typically scattered on south-facing slopes and mountain tops, on calcareous (limestone) and rocky soils at approx. 1300 m elevation.

Pseudotsuga forrestii - Yunnan, where it is found in the mountains at 2400-3300 m elevation

 Source: Pseudotsuga, The Gymnosper Database (original sources removed). and IUCN, Red List

Economic Importance for Humans

caption Coast Douglas-fir. source: wikimedia Commons.

Coast Douglas-fir is a most important timber tree, valued in both the Old and New worlds. The two intergrading varieties are sympatric in southern British Columbia and northeastern Washington. it was used by Westerners for telephone poles and railway ties among many other uses. Today, Douglas-fir is also grown for Christmas trees.

Ethnobotanic:

  • Douglas-fir needles were made into a tea and drank by Isleta Puebloans in New Mexico to cure rheumatism.

  • Douglas-fir resin was used by the Shasta in northern California to poultice cuts and the Yuki along the California coast used a decoction from spring buds to treat venereal diseases.

  • The Sinkyone of California made Douglas-fir bark tea which eased colds and stomach ailments.

  • The Kayenta Navaho of Arizona used the tree to treat stomach disease and headaches, although what part of the plant was used is not known. Also, historically the Kayenta Navajo ground part of tree with a certain rock and mixed it with corn seeds to insure a good crop.

  • The Pueblo people used the wood to construction dwellings while the twigs were worn on various parts of dancers' costumes. Prayer sticks made of Douglas-fir wood were excavated from archeological sites in New Mexico dating back to the Anasazi.

  • The White Mountain Apache used the pitch of this conifer as gum and applied it to water jugs to make them watertight. Douglas-fir roots were used in California Indian basketry.

Bigcone Douglas-fir is a tree of scattered occurrence and of no concern for timber, but is valuable for esthetics and watershed protection.

Threats & Conservation Status

Bigcone Douglas-fir (Pseudotsuga macrocarpa) Lower Risk/near threatened
Coast Douglas-fir (Pseudotsuga menziesii) Least concern
Japanese Douglas-fir (Pseudotsuga japonica) Vulnerable
Chinese Douglas-fir (Pseudotsuga sinensis) Vulnerable - The timber is extracted extensively throughout the species' range but most thoroughly in accessible areas. Trees are also being lost through habitat destruction for expanding agricultural activities. In Taiwan the forest is being extensively cleared for apple and peach orchards. The timber is extracted extensively throughout the species' range but most thoroughly in accessible areas.

 Source:  Conifer Specialist Group 1998. Pseudotsuga sinensis. In: IUCN 2011. IUCN Red List of Threatened Species.

Further Reading

 

Glossary

Citation

Life, E. (2013). Douglas-fir . Retrieved from http://www.eoearth.org/view/article/51cbf26d7896bb431f6a945b

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