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 Pseudotsuga menziesii var. menziesii in Anacortes Community Forest Lands, Washington | ||||||||||||
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Douglas-fir is the English name applied in common to evergreen coniferous trees of the genus Pseudotsuga (pronounced /ˌsjuːdoʊˈtsuːɡə/)[1] in the family Pinaceae. There are five species, two in western North America, one in Mexico, and two in eastern Asia. 19th Century botanists had problems in classifying Douglas-firs due to the species' similarity to various other conifers better known at the time; they have at times been classified in Pinus, Picea, Abies, Tsuga, and even Sequoia. Because of its distinctive cones, Douglas-firs were finally placed in the new genus Pseudotsuga (meaning "false Tsuga") by the French botanist Carrière in 1867. The genus name has also been hyphenated as Pseudo-tsuga.
The common name honours David Douglas, the Scottish botanist who first introduced P. menziesii into cultivation in 1826. Douglas is known for introducing many North American native conifers to Europe. The hyphen in the name indicates that Douglas-firs are not true firs, not being members of the genus Abies.[2]
Douglas-firs are medium-size to large or very large evergreen trees, 20-120 m tall. The leaves are flat and linear, generally resembling those of the firs. The female cones are pendulous, with persistent scales (unlike true firs), and are distinctive in having a long tridentine (three-pointed) bract that protrudes prominently above each scale.
Douglas-firs are used as food plants by the larvae of some Lepidoptera species including Autumnal Moth, Bordered White, The Engrailed, Pine Beauty, Turnip Moth, and the gelechiids Chionodes abella and Chionodes periculella which have both been recorded on P. menziesii.
A California Native American myth explains that each of the three-ended bracts are a tail and two tiny legs of the mice who hid inside the scales of the tree's cones during forest fires, and the tree was kind enough to be the enduring sanctuary for them.
Species and varieties
By far the best-known is the very widespread and abundant North American species Pseudotsuga menziesii, a taxonomically complex species[3] divided into two major varieties (treated as distinct species or subspecies by some botanists): Coast Douglas-fir or "Green Douglas-fir", on the Pacific coast; and Rocky Mountain Douglas-fir or "Interior Douglas-fir", in the interior west of the continent extending as far inland as Calgary, Alberta[4]. Some botanists divide the latter in turn into two varieties, "Blue Douglas-fir" or "Colorado Douglas-fir" (var. glauca) in the southern Rocky Mountains, and "Gray Douglas-fir" or "Fraser River Douglas-fir" (var. caesia) in the northern Rocky Mountains. The species as a whole is generally known as simply "Douglas-fir", or as "Common Douglas-fir"; other less widely used names include "Oregon Douglas-fir", "Douglas Tree", and "Oregon Pine". It is the state tree of Oregon.
Coast Douglas-fir has attained heights of 393 ft (120 m). That was the estimated height of the tallest conifer ever well-documented, the Mineral Tree (Mineral, Washington), measured in 1924 by Dr. Richard E. McArdle[5], former chief of the U.S. Forest Service[6]. The volume of that tree was 515 cubic metres (18,190 cu ft). The tallest living individual is the Brummitt (Doerner) Fir in Coos County, Oregon, 99.4 metres (326 ft) tall[7]. Only Coast Redwood[8] reach greater heights based on current knowledge of living trees. At Quinault, Washington, is found a collection of the largest Douglas Firs in one area. Quinault Rain Forest hosts the most of the top ten known largest Douglas Firs.
All of the other species are of restricted range and little-known outside of their respective native environments, and even there are often rare and only of very scattered occurrence in mixed forests; all those are listed as being of unfavourable conservation status.
- North America
- Coast Douglas-fir, Pseudotsuga menziesii var. menziesii
- Rocky Mountain Douglas-fir, Pseudotsuga menziesii var. glauca
- Mexican Douglas-fir, Pseudotsuga lindleyana
- Bigcone Douglas-fir, Pseudotsuga macrocarpa
- Asia
- Japanese Douglas-fir, Pseudotsuga japonica
- Chinese Douglas-fir, Pseudotsuga sinensis var. sinensis
- Narrow-cone Chinese Douglas-fir, Pseudotsuga sinensis var. gaussenii
- Short-leaf Chinese Douglas-fir, Pseudotsuga sinensis var. brevifolia
- Yunnan Douglas-fir, Pseudotsuga sinensis var. forrestii
- Taiwan Douglas-fir, Pseudotsuga sinensis var. wilsoniana
Uses
Douglas-fir wood is used for structural applications that are required to withstand high loads. It is used extensively in the construction industry. Other examples include its use for homebuilt aircraft such as the RJ.03 IBIS canard. Very often, these aircraft were designed to utilize Sitka spruce, which is becoming increasingly difficult to source in aviation quality grades.
Douglas-fir is the most commonly marketed Christmas tree species in the United States, where they are sold along with firs like Noble Fir and Grand Fir. Douglas-fir Christmas trees are usually trimmed to a near perfect cone instead of left to grow naturally like Noble and Grand firs.[9]
Diseases
Douglas-fir is attacked by a number of fungal diseases.
See also
References
- ^ Sunset Western Garden Book, 1995:606–607
- ^ Little, E. L. (1953). Check List of native and naturalized trees of the United States (including Alaska). Washington D.C.: U.S. Department of Agriculture. USDA Agricultural Handbook 41.
- ^ Li, Peng; W. T. Adams (1989). "Rangewide patterns of allozyme variation in Douglas-fir". Canad. J. Forest Res. 19: 149–161. doi:.
- ^ Edworthy Park - Calgary, Alberta - Wikipedia Entries on Waymarking.com
- ^ Forest Giants of the World Past and Present by Al Carder 1995, pg. 3-4.
- ^ USFS History-Forest History Society[1]
- ^ Gymnosperm Database: Pseudotsuga menziesii var. menziesii (2006)
- ^ "Sequoia sempervirens". The Gymnosperm Database. http://www.conifers.org/cu/se/index.htm. Retrieved on 2009-02-01.
- ^ National Christmas Tree Assoc http://www.christmastree.org/trees/douglas.cfm
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