| Pseudotsuga | |
|---|---|
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| Pseudotsuga menziesii var.menziesii inAnacortes Community Forest Lands,Washington | |
Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Gymnospermae |
| Division: | Pinophyta |
| Class: | Pinopsida |
| Order: | Pinales |
| Family: | Pinaceae |
| Subfamily: | Laricoideae |
| Genus: | Pseudotsuga Carrière |
| Type species | |
| Pseudotsuga douglasii (Lindl.)Carrière | |
| Species | |
See text | |
| Synonyms | |
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Pseudotsuga (/ˌsjuːdoʊˈtsuːɡə/[1]) is a genus ofevergreenconiferoustrees in the familyPinaceae (subfamilyLaricoideae). Common names for species in the genus includeDouglas fir,Douglas-fir,Douglas tree,Oregon pine andBigcone spruce.Pseudotsuga menziesii (Douglas fir proper) is widespread in western North America and is an important source of timber. The number of species has long been debated, but two in westernNorth America and two to four in easternAsia are commonly acknowledged.[2][3]
Nineteenth-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 inPinus,Picea,Abies,Tsuga, and evenSequoia. Because of their distinctive cones, Douglas firs were finally placed in the new genusPseudotsuga (meaning "false hemlock") by the French botanistCarrière in 1867. The genus name has also been hyphenated asPseudo-tsuga.
The tree takes its English name fromDavid Douglas, theScottishbotanist who first introducedPseudotsuga menziesii into cultivation atScone Palace in 1827.[4] Douglas is known for introducing many native American tree species to Europe. The hyphenated form "Douglas-fir" is used by some to indicate thatPseudotsuga species are not truefirs, which belong to the genusAbies.[5]
Douglas-firs are medium-size to extremely largeevergreentrees, 20–120 metres (70–390 ft) tall (although only coast Douglas-firs reach such great height).[6] Theleaves are flat, soft, linear, 2–4 centimetres (0.8–1.6 in) long, generally resembling those of the firs, occurring singly rather than infascicles; they completely encircle the branches, which can be useful in recognizing the species. The femalecones 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 (it resembles the back half of a mouse, with two feet and a tail).
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Pseudotsuga menziesii var.menziesii has attained heights of 393 feet (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,[7] former chief of the U.S. Forest Service.[8] The volume of that tree was 515 cubic metres (18,190 cu ft). The tallest living individual is the Brummitt (Doerner) Fir inCoos County, Oregon, 99.4 metres (326 ft) tall.[9] Onlycoast redwood[10] andEucalyptus regnans reach greater heights based on current knowledge of living trees: 379 and 331 feet (116 and 101* m), respectively.At Quinault, Washington, is found a collection of the largest Douglas-firs in one area. Quinault Rain Forest hosts most of the top ten known largest Douglas-firs.
As of 2009[update], the largest known Douglas-firs in the world are, by volume:[11]
Phylogeny ofPseudotsuga according to Stull 2021:[12][13]
| Pseudotsuga |
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By far the best-known is the widespread and abundantNorth American speciesPseudotsuga menziesii, a taxonomically complex species[14] divided into two majorvarieties (treated as distinctspecies orsubspecies by some botanists):coast Douglas-fir or "green Douglas-fir", on thePacific coast; andRocky Mountain Douglas-fir or "interior Douglas-fir", in the interior west of the continent. According to some botanists, Rocky Mountain Douglas-fir extends south into Mexico to include allMexican Douglas-fir populations,[15] whereas others have proposed multiple separate species in Mexico[16][17][18] and multiple varieties in the United States. Morphological and genetic evidence suggest that Mexican Douglas-fir should probably be considered a distinct variety withinP. menziesii.[19][20][21]
All of the other species are of restricted range and little-known outside of their respective native environments, where they are often rare and of scattered occurrence in mixed forests; all those have unfavorableconservation status. The taxonomy of the Asian Douglas-firs continues to be disputed,[22] but the most recent taxonomic treatment accepts four species: three Chinese and one Japanese.[2][3] The three Chinese species have been variously considered varieties ofP. sinensis[23] or broken down into additional species and varieties.[24] In the current treatment, the Chinese speciesP. sinensis is further subdivided into two varieties: var.sinensis and var.wilsoniana.
Douglas-firwood 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 homebuiltaircraft such as the RJ.03 IBIS canard. Very often, these aircraft were designed to utilizeSitka spruce, which is becoming increasingly difficult to source in aviation quality grades. Oregon pine is also used inboat building when it is available in long, fairlyknot-free lengths. Most timber now comes from plantation forests in North America which are managed to produce faster growing timber with fewer knots. This timber is generally lighter but weaker. Traditionally, Oregon pine was used inmast building due to its ability to resist bending loads without fracturing. This was based on using older native forest wood with a high number of growth rings per inch. This sort of wood is seldom available new but can be sourced from merchants dealing inrecycled timber. Native Oregon pine is considerably heavier thanSitka spruce, which is about the same weight aswestern red cedar, but with far better bending characteristics than cedar. Large-sized Oregon pine, as used in beams, is inclined to split as it dries, like oak, but this does not reduce its strength.
Douglas-fir is one of the most commonly marketedChristmas tree species in the United States, where they are sold alongside firs likenoble fir andgrand fir. Douglas-fir Christmas trees are usually trimmed to a near perfect cone instead of left to grow naturally like noble and grand firs.[25]
Douglas-firs are used as food plants by thelarvae of someLepidoptera species, includingautumnal moth,bordered white,engrailed moth,pine beauty andturnip moth. ThegelechiidsChionodes abella andChionodes periculella and thetortrix mothCydia illutana have been specifically recorded onP. menziesii.
A CaliforniaNative American myth explains that each three-ended bract is the tail and two tiny legs of amouse that hid inside the scales of the tree's cones during forest fires, and the tree was kind enough to be its enduring sanctuary.
A Douglas-fir species,Pseudotsuga menziesii, is thestate tree ofOregon.
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