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An oak is a hardwood tree or shrub in the genus Quercus of the beech family. They have spirally arranged leaves, often with lobed edges, and a nut called an acorn, borne within a cup. The genus is widely distributed in the Northern Hemisphere; it includes some 500 species, both deciduous and evergreen. Fossil oaks date back to the Middle Eocene. Molecular phylogeny shows that the genus is divided into Old World and New World clades, but many oak species hybridise freely, making the genus's history difficult to resolve.
Ecologically, oaks are keystone species in habitats from Mediterranean semi-desert to subtropical rainforest. They live in association with many kinds of fungi including truffles. Oaks support more than 950 species of caterpillar, many kinds of gall wasp which form distinctive galls (roundish woody lumps such as the oak apple), and a large number of pests and diseases. Oak leaves and acorns contain enough tannin to be toxic to cattle, but pigs are able to digest them safely. Oak timber is strong and hard, and has found many uses in construction and furniture-making. The bark was traditionally used for tanning leather. Wine barrels are made of oak; these are used for aging alcoholic beverages such as sherry and whisky, giving them a range of flavours, colours, and aromas. The spongy bark of the cork oak is used to make traditional wine bottle corks. Almost a third of oak species are threatened with extinction due to climate change, invasive pests, and habitat loss.
In culture, the oak tree is a symbol of strength and serves as the national tree of many countries. In Indo-European and related religions, the oak is associated with thunder gods. Individual oak trees of cultural significance include the Royal Oak in Britain, the Charter Oak in the United States, and the Guernica Oak in the Basque Country.
EtymologyEdit
The generic name Quercus is Latin for "oak", derived from Proto-Indo-European *kwerkwu-, "oak", which is also the origin of the name "fir", another important or sacred tree in Indo-European culture. The word "cork", for the bark of the cork oak, similarly derives from Quercus.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The common name "oak" is from Old English ac (seen in placenames such as Acton, from ac + tun, "oak village"),<ref>Template:Cite book</ref> which in turn is from Proto-Germanic *aiks, "oak".<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
DescriptionEdit
Oaks are hardwood (dicotyledonous) trees, deciduous or evergreen, with spirally arranged leaves, often with lobate margins; some have serrated leaves or entire leaves with smooth margins. Many deciduous species are marcescent, not dropping dead leaves until spring. In spring, a single oak tree produces both male and female flowers. The staminate (male) flowers are arranged in catkins, while the small pistillate (female) flowers<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> produce an acorn (a kind of nut) contained in a cupule. Each acorn usually contains one seed and takes 6–18 months to mature, depending on the species. The acorns and leaves contain tannic acid,<ref>Template:Cite book</ref> which helps to guard against fungi and insects.<ref>Template:Cite book</ref> There are some 500 extant species of oaks.<ref name=powo>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Trees in the genus are often large and slow-growing; Q. alba can reach an age of 600 years, a diameter of Template:Convert and a height of Template:Convert.<ref name="Core">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The Granit oak in Bulgaria, a Q. robur specimen, has an estimated age of 1,637 years, making it the oldest oak in Europe.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The Wi'aaSal tree, a live oak in the reservation of the Pechanga Band of Indians, California, is at least 1,000 years old, and might be as much as 2,000 years old, which would make it the oldest oak in the US.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Among the smallest oaks is Q. acuta, the Japanese evergreen oak. It forms a bush or small tree to a height of some Template:Convert.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
- Brockwell Oak (9).jpg
Quercus robur habit
- Quercus lusitanica - Köhler–s Medizinal-Pflanzen-253.jpg
Illustration of Q. lusitanica showing staminate (left) and pistillate flowers (right)
- 2021-04-22 18 54 32 Male flowers (catkins) on a White Oak within a wooded area in the Franklin Farm section of Oak Hill, Fairfax County, Virginia.jpg
Catkins of Q. alba containing the staminate or 'male' flowers
- Летен дъб - цъфтеж, нови листа.JPG
New leaves and reddish pistillate or 'female' flowers of Q. robur
DistributionEdit
The genus Quercus is native to the Northern Hemisphere and includes deciduous and evergreen species extending from cool temperate to tropical latitudes in the Americas, Asia, Europe, and North Africa. North America has the largest number of oak species, with approximately 160 species in Mexico, of which 109 are endemic, and about 90 in the United States. The second greatest area of oak diversity is China, with approximately 100 species.<ref>Hogan, C. Michael (2012) "Oak" Template:Webarchive. ed. Arthur Dawson. Encyclopedia of Earth. National Council for Science and the Environment. Washington DC</ref>
In the Americas, Quercus is widespread from Vancouver and Nova Scotia in the south of Canada, south to Mexico and across the whole of the eastern United States. It is present in a small area of the west of Cuba; in Mesoamerica it occurs mainly above Template:Convert.<ref name="Nixon 2006"/> The genus crossed the isthmus of Panama when the northern and southern continents came together<ref name="Hooghiemstra 2006">Template:Cite book</ref> and is present as one species, Q. humboldtii, above 1,000 metres in Colombia.<ref name="Nixon 2006">Template:Cite book</ref> The oaks of North America are of many sections (Protobalanus, Lobatae, Ponticae, Quercus, and Virentes) along with related genera such as Notholithocarpus.<ref name="Liu Yang Tian Yang 2023"/>
In the Old World, oaks of section Quercus extend across the whole of Europe including European Russia apart from the far north, and north Africa (north of the Sahara) from Morocco to Libya. In Mediterranean Europe, they are joined by oaks of the sections Cerris and Ilex, which extend across Turkey, the Middle East, Iran, Afghanistan and Pakistan, while section Ponticae is endemic to the western Caucasus in Turkey and Georgia. Oaks of section Cyclobalanopsis extend in a narrow belt along the Himalayas to cover mainland and island Southeast Asia as far as Sumatra, Java, Borneo, and Palawan.<ref name=powo/><ref>Template:Cite journal</ref> Finally, oaks of multiple sections (Cyclobalanopsis, Ilex, Cerris, Quercus and related genera like Lithocarpus and Castanopsis) extend across east Asia including China, Korea, and Japan.<ref name="Liu Yang Tian Yang 2023">Template:Citation</ref>
EvolutionEdit
Fossil historyEdit
Potential records of Quercus have been reported from Late Cretaceous deposits in North America and East Asia. These are not considered definitive, as macrofossils older than the Paleogene, and possibly from before the Eocene are mostly poorly preserved without critical features for certain identification. Amongst the oldest unequivocal records of Quercus are pollen from Austria, dating to the Paleocene-Eocene boundary, around 55 million years ago. The oldest records of Quercus in North America are from Oregon, dating to the Middle Eocene, around 44 million years ago, with the oldest records in Asia from the Middle Eocene of Japan; both forms have affinities to the Cyclobalanopsis group.<ref>Template:Citation</ref>
- Quercus hispanica 20170317.jpg
Quercus × hispanica leaf. Miocene, Lleida, Spain
- Quercus hiholensis acorn UWBM 56470-3 Pigg & Wehr 2002 Plt2 fig16.png
Quercus hiholensis acorn, Langhian age (Middle Miocene), Washington State, US (c. 15 mya)
- Quercus kobatakei leaf (cropped).jpg
Quercus kobatakei leaf. Early Oligocene, Japan
- Early Oligocene oak acorn from Bridge Creek Flora.jpg
Early Oligocene acorn, Oregon, US (33 mya)
External phylogenyEdit
Quercus forms part, or rather two parts, of the Quercoideae subfamily of the Fagaceae, the beech family. Modern molecular phylogenetics suggests the following relationships:<ref name="Manos Cannon Oh 2008">Template:Cite journal</ref><ref name="Xiang Wang Li 2014">Template:Cite journal</ref>
Internal phylogenyEdit
Molecular techniques for phylogenetic analysis show that the genus Quercus consisted of Old World and New World clades.<ref name=":0"/><ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> The entire genome of Quercus robur (the pedunculate oak) has been sequenced,<ref>Template:Cite journal</ref> revealing an array of mutations that may underlie the evolution of longevity and disease resistance in oaks.<ref>Template:Cite journal</ref> In addition, hundreds of oak species have been compared (at RAD-seq loci), allowing a detailed phylogeny to be constructed. However, the high signal of introgressive hybridization (the transfer of genetic material by repeated backcrossing with hybrid offspring) in the genus has made it difficult to resolve an unambiguous, unitary history of oaks. The phylogeny from Hipp et al. 2019 is:<ref>Template:Cite journal</ref>
TaxonomyEdit
Taxonomic historyEdit
The genus Quercus was circumscribed by Carl Linnaeus in the first edition of his 1753 Species Plantarum.<ref>Template:Cite journal</ref> He described 15 species within the new genus, providing type specimens for 10 of these, and giving names but no types for Q. cerris, Q. coccifera, Q. ilex, Q. smilax, and Q. suber.<ref>Template:Cite journal</ref> He chose Q. robur, the pedunculate oak, as the type species for the genus.<ref>Template:Cite journal</ref>
A 2017 classification of Quercus, based on multiple molecular phylogenetic studies, divided the genus into two subgenera and eight sections:<ref name=DenkGrimManoDeng17>Template:Citation</ref>
- Subgenus Quercus – the New World clade (or high-latitude clade), mostly native to North America
- Section Lobatae Loudon – North American red oaks
- Section Protobalanus (Trelease) O.Schwarz – North American intermediate oaks
- Section Ponticae Stef. – with a disjunct distribution between western Eurasia and western North America
- Section Virentes Loudon – American southern live oaks
- Section Quercus – white oaks from North America and Eurasia
- Subgenus Cerris Oerst. – the Old World clade (or mid-latitude clade), exclusively native to Eurasia
- Section Cyclobalanopsis Oerst. – cycle-cup oaks of East Asia
- Section Cerris Dumort. – cerris oaks of subtropical and temperate Eurasia and North Africa
- Section Ilex Loudon – ilex oaks of tropical and subtropical Eurasia and North Africa
The subgenus division supports the evolutionary diversification of oaks among two distinct clades: the Old World clade (subgenus Cerris), including oaks that diversified in Eurasia; and the New World clade (subgenus Quercus), oaks that diversified mainly in the Americas.<ref name=":0">Template:Cite journal</ref><ref name="Manos Hipp 2021">Template:Cite journal</ref>
Subgenus QuercusEdit
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- Sect. Lobatae (synonym Erythrobalanus), the red oaks of North America, Central America and northern South America. Styles are long; the acorns mature in 18 months and taste very bitter. The inside of the acorn shell appears woolly. The actual nut is encased in a thin, clinging, papery skin. The leaves typically have sharp lobe tips, with spiny bristles at the lobe.<ref name=DenkGrimManoDeng17/>
- Sect. Protobalanus, the canyon live oak and its relatives, in the southwestern United States and northwest Mexico. Styles are short; the acorns mature in 18 months and taste very bitter. The inside of the acorn shell appears woolly. The leaves typically have sharp lobe tips, with bristles at the lobe tip.<ref name=DenkGrimManoDeng17/>
- Sect. Ponticae, a disjunct including just two species. Styles are short, and the acorns mature in 12 months. The leaves have large stipules, high secondary veins, and are highly toothed.<ref name=DenkGrimManoDeng17/>
- Sect. Virentes, the southern live oaks of the Americas. Styles are short, and the acorns mature in 12 months. The leaves are evergreen or subevergreen.<ref name=DenkGrimManoDeng17/>
- Sect. Quercus (synonyms Lepidobalanus and Leucobalanus), the white oaks of Europe, Asia and North America. Trees or shrubs that produce nuts, specifically acorns, as fruits. Acorns mature in one year for annual trees and two years for biannual trees. Acorn is encapsulated by a spiny cupule as characterized by the family Fagaceae. Flowers in the Quercus genera produce one flower per node, with three or six styles, as well as three or six ovaries, respectively. The leaves mostly lack a bristle on their lobe tips, which are usually rounded. The type species is Quercus robur.<ref name=DenkGrimManoDeng17/><ref>Template:Cite book</ref>
Subgenus CerrisEdit
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The type species is Quercus cerris.
- Sect. Cyclobalanopsis, the ring-cupped oaks of eastern and southeastern Asia. These are evergreen trees growing Template:Convert tall. They are distinct from subgenus Quercus in that they have acorns with distinctive cups bearing concrescent rings of scales; they commonly also have densely clustered acorns, though this does not apply to all of the species. Species of Cyclobalanopsis are common in the evergreen subtropical laurel forests, which extend from southern Japan, southern Korea, and Taiwan across southern China and northern Indochina to the eastern Himalayas, in association with trees of the genus Castanopsis and the laurel family (Lauraceae).<ref name=DenkGrimManoDeng17/>
- Sect. Cerris, the Turkey oak and its relatives of Europe and Asia. Styles are long; acorns mature in 18 months and taste very bitter. The inside of the acorn's shell is hairless. Its leaves typically have sharp lobe tips, with bristles at the lobe tip.<ref name=DenkGrimManoDeng17/>
- Sect. Ilex, the Ilex oak and its relatives of Eurasia and northern Africa. Styles are medium-long; acorns mature in 12–24 months, appearing hairy on the inside. The leaves are evergreen, with bristle-like extensions on the teeth.<ref name=DenkGrimManoDeng17/>
EcologyEdit
Oaks are keystone species in a wide range of habitats from Mediterranean semi-desert to subtropical rainforest. They are important components of hardwood forests; some species grow in associations with members of the Ericaceae in oak–heath forests.<ref>The Natural Communities of Virginia Classification of Ecological Community Groups (Version 2.3), Virginia Department of Conservation and Recreation, 2010 Template:Webarchive. Dcr.virginia.gov. Retrieved 2011-12-10.</ref><ref>Schafale, M. P. and A. S. Weakley. 1990. Classification of the natural communities of North Carolina: third approximation. North Carolina Natural Heritage Program, North Carolina Division of Parks and Recreation.</ref> Several kinds of truffles, including two well-known varieties – black Périgord truffle<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> and the white Piedmont truffle<ref name=r13>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> – have symbiotic relationships with oak trees. Similarly, many other fungi, such as Ramaria flavosaponaria, associate with oaks.<ref name="Nirschl">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="Petersen">Template:Cite journal</ref>
Oaks support more than 950 species of caterpillars, an important food source for many birds.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Mature oak trees shed widely varying numbers of acorns (known collectively as mast) annually, with large quantities in mast years. This may be a predator satiation strategy, increasing the chance that some acorns will survive to germination.<ref name="Bogdziewicz Marino Bonal Zwolak 2018 pp. 2575–2582">Template:Cite journal</ref>
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Animals including squirrels<ref name="Steele Yi 2020">Template:Cite journal</ref> and jays – Eurasian jays in the Old World, blue jays in North America – feed on acorns, and are important agents of seed dispersal as they carry the acorns away and bury many of them as food stores.<ref name="Mitrus Szabo 2020">Template:Cite journal</ref><ref name="Enroth 2022">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="Bossema 1979">Template:Cite journal</ref> However, some species of squirrel selectively excise the embryos from the acorns that they store, meaning that the food store lasts longer and that the acorns will never germinate.<ref name="Steele Yi 2020"/>
HybridisationEdit
Interspecific hybridization is quite common among oaks, but usually between species within the same section only,<ref>Template:Cite journal</ref> and most common in the white oak group. White oaks cannot discriminate against pollination by other species in the same section. Because they are wind pollinated and have weak internal barriers to hybridization, hybridization produces functional seeds and fertile hybrid offspring. Ecological stresses, especially near habitat margins, can also cause a breakdown of mate recognition as well as a reduction of male function (pollen quantity and quality) in one parent species.<ref>Template:Cite journal</ref><ref>Template:Cite book</ref>
Frequent hybridization among oaks has consequences for oak populations around the world; most notably, hybridization has produced large populations of hybrids with much introgression and the evolution of new species.<ref name=r2>Template:Cite journal</ref> Introgression has caused different species in the same populations to share up to 50% of their genetic information.<ref name=r3>Template:Cite journal</ref> As a result, genetic data often does not differentiate between clearly morphologically distinct species, but instead differentiates populations.<ref name=r4>Template:Cite journal</ref> The maintenance of particular loci for adaptation to ecological niches may explain the retention of species identity despite significant gene flow.<ref>Template:Cite journal</ref>
The Fagaceae, or beech family, to which the oaks belong, is a slowly-evolving clade compared to other angiosperms,<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> and the patterns of hybridization and introgression in Quercus pose a significant challenge to the concept of a species as a group of "actually or potentially interbreeding populations which are reproductively isolated from other such groups."<ref name="Raven 2005"/> By this definition, many species of Quercus would be lumped together according to their geographic and ecological habitat, despite clear distinctions in morphology and genetic data.<ref name="Raven 2005">Template:Cite book</ref>
Diseases and pestsEdit
Oaks are affected by a large number of pests and diseases. For instance, Q. robur and Q. petraea in Britain host 423 insect species.<ref name="Kennedy Southwood 1984">Template:Cite journal</ref> This diversity includes 106 macro-moths, 83 micro-moths, 67 beetles, 53 cynipoidean wasps, 38 heteropteran bugs, 21 auchenorrhynchan bugs, 17 sawflies, and 15 aphids.<ref name="Kennedy Southwood 1984"/> The insect numbers are seasonal: in spring, chewing insects such as caterpillars become numerous, followed by insects with sucking mouthparts such as aphids, then by leaf miners, and finally by gall wasps such as Neuroterus.<ref>Template:Cite journal</ref> Several powdery mildews affect oak species. In Europe, the species Erysiphe alphitoides is the most common.<ref>Template:Cite journal</ref> It reduces the ability of leaves to photosynthesize, and infected leaves are shed early.<ref name="Hajji Dreyer 2009">Template:Cite journal</ref> Another significant threat, the oak processionary moth (Thaumetopoea processionea), has emerged in the UK since 2006. The caterpillars of this species defoliate the trees and are hazardous to human health; their bodies are covered with poisonous hairs which can cause rashes and respiratory problems.<ref name=forestry>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> A little-understood disease of mature oaks, acute oak decline, has affected the UK since 2009.<ref>Template:Cite news</ref> In California, goldspotted oak borer (Agrilus auroguttatus) has destroyed many oak trees,<ref name="Coleman 2008">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> while sudden oak death, caused by the oomycete pathogen Phytophthora ramorum, has devastated oaks in California and Oregon, and is present in Europe.<ref name="Scientific Societies 2008">Template:Cite journal</ref> Japanese oak wilt, caused by the fungus Raffaelea quercivora, has rapidly killed trees across Japan.<ref name="Kuroda Yamada 1996">Template:Cite journal</ref>
Gall communitiesEdit
Many galls are found on oak leaves, buds, flowers, and roots. Examples are oak artichoke gall, oak marble gall, oak apple gall, knopper gall, and spangle gall. These galls are the handiwork of tiny wasps from the Cynipidae. In a complex ecological relationship, these gall wasps become hosts to parasitoid wasps—primarily from the order Chalcidoidea—which lay their larvae inside the gall wasps, ultimately leading to the hosts' demise. Additionally, inquilines live commensally within the galls without harming the gall wasps.<ref>Template:Cite journal</ref>
- Gallrazorback.jpg
Oak apple gall on Quercus garryana
- Oak apples on oak leaf and in cross section.JPG
Oak apples on oak leaf
- Biorhiza pallida male.jpg
Biorhiza pallida male, the cause of oak apple galls
ToxicityEdit
The leaves and acorns of oaks are poisonous to livestock, including cattle and horses, if eaten in large amounts, due to the toxin tannic acid, which causes kidney damage and gastroenteritis.<ref>Template:Cite journal</ref><ref name="Smith Naylor Knowles Mair 2014">Template:Cite journal</ref> An exception is the domestic pig, which, under the right conditions, may be fed entirely on acorns,<ref>Cappai, Maria Grazia, et al. "Pigs use endogenous proline to cope with acorn (Quercus pubescens Willd.) combined diets high in hydrolysable tannins." Livestock Science 155.2-3 (2013): 316–322.</ref> and has traditionally been pastured in oak woodlands (such as the Spanish dehesa<ref>Joffre, R; Rambal, S.; Ratte, J.P. (1999). "The dehesa system of southern Spain and Portugal as a natural ecosystem mimic," Journal of Agroforestry 45(1-3): 57-79.</ref> and the English system of pannage).<ref>Template:Cite book</ref> Humans can eat acorns after leaching out the tannins in water.<ref>Template:Citation</ref>
UsesEdit
TimberEdit
Oak timber is a strong and hard wood with many uses, such as for furniture, floors, building frames, and veneers.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The wood of Quercus cerris (the Turkey oak) has better mechanical properties than those of the white oaks Q. petraea and Q. robur; the heartwood and sapwood have similar mechanical properties.<ref>Merela, Maks, and Katarina Čufar. "Density and mechanical properties of oak sapwood versus heartwood in three different oak species". Drvna industrija 64.4 (2013): 323–334.</ref> Of the North American red oaks, the northern red oak, Quercus rubra, is highly prized for lumber.<ref>Aldrich, Preston R., et al. "Whole-tree silvic identifications and the microsatellite genetic structure of a red oak species complex in an Indiana old-growth forest." Canadian Journal of Forest Research 33.11 (2003): 2228–2237.</ref><ref>Template:EFloras</ref> The wood is resistant to insect and fungal attack.<ref>Thaler, Nejc; Humar, Miha. "Performance of oak, beech and spruce beams after more than 100 years in service". International Biodeterioration & Biodegradation 85 (2013): 305–310.</ref>
Wood from Q. robur and Q. petraea was used in Europe for shipbuilding, especially of naval men of war, until the 19th century.<ref>Template:Cite book</ref> In hill states of India such as Uttarakhand, along with being used for fuelwood and timber, oak wood is used for agricultural implements, while the leaves serve as fodder for livestock during lean periods.<ref>Kala, C.P. (2004). Studies on the indigenous knowledge, practices, and traditional uses of forest products by human societies in Uttarakhand state of India. GBPIHED, Almora, India</ref><ref>Kala, C.P. (2010). Medicinal Plants of Uttarakhand: Diversity Livelihood and Conservation. BioTech Books, Delhi, Template:ISBN.</ref>
Other traditional productsEdit
Oak bark, with its high tannin content, was traditionally used in the Old World for tanning leather.<ref>Clarkson, L. A. "The English bark trade, 1660–1830" The Agricultural History Review 22.2 (1974): 136–152. Template:JSTOR</ref> Oak galls were used for centuries as a main ingredient in iron gall ink for manuscripts, harvested at a specific time of year.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> In Korea, sawtooth oak bark is used to make shingles for traditional roof construction.<ref name="Jeon 2016">Template:Cite book</ref> The dried bark of the white oak was used in traditional medical preparations; its tannic acid content made it astringent and antiseptic.<ref>Henkel, Alice. American medicinal barks. No. 139. US Government Printing Office, 1909.</ref> Acorns have been ground to make a flour,<ref>Szabłowska, Emilia; Tańska, Małgorzata. "Acorn flour properties depending on the production method and laboratory baking test results: A review." Comprehensive Reviews in Food Science and Food Safety 20.1 (2021): 980-1008.</ref> and roasted for acorn coffee.<ref>Template:Cite journal</ref>
CulinaryEdit
Barrels for aging wines, sherry, and spirits such as brandy and Scotch whisky are made from oak, with single barrel malt whiskies fetching a premium.<ref name="Piggott 2003">Piggott, John R.; Conner, John M. "Whiskies." Fermented beverage production. Boston, Massachusetts: Springer, 2003. 239–262.</ref> The use of oak in wine adds a range of flavours. Oak barrels, which may be charred before use, contribute to their contents' colour, taste, and aroma, imparting a desirable oaky vanillin flavour. A dilemma for wine producers is to choose between French and American oakwoods. French oaks (Quercus robur, Q. petraea) give greater refinement and are chosen for the best, most expensive wines. American oak contributes greater texture and resistance to ageing, but produces a more powerful bouquet.<ref>Pérez-Prieto, Luis J., et al. "Extraction and formation dynamic of oak-related volatile compounds from different volume barrels to wine and their behavior during bottle storage." Journal of Agricultural and Food Chemistry 51.18 (2003): 5444–5449.</ref><ref>Perez‐Prieto, Luis Javier, et al. "Oak‐matured wines: influence of the characteristics of the barrel on wine colour and sensory characteristics." Journal of the Science of Food and Agriculture 83.14 (2003): 1445–1450.</ref>
Oak wood chips are used for smoking foods such as fish, meat, and cheese.<ref name="Varlet Prost Serot 2007">Template:Cite journal</ref><ref>Template:Cite journal</ref> In Japan, Children's Day is celebrated with Template:Transliteration rice cakes, filled with a sweet red bean paste, and wrapped in a Template:Transliteration oak leaf.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The bark of the cork oak is used to produce cork stoppers for wine bottles. This species grows around the Mediterranean Sea; Portugal, Spain, Algeria, and Morocco produce most of the world's supply.<ref name="Amorim">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
Acorns of various oak species have been used as food for millennia, in Asia, Europe, the Middle East, North Africa, and among the native peoples of North America. In North Africa, acorns have been pressed to make acorn oil: the oil content can be as high as 30%. Oaks have also been used as fodder, both leaves and acorns being fed to livestock such as pigs. Given their high tannin content, acorns have often been leached to remove tannins before use as fodder.<ref>Template:Cite journal</ref>
- Sherry cellar, Solera system, 2003.jpg
Sherry maturing in oak barrels
- Cork oak trunk section.jpg
A cross section of the trunk of a cork oak, Quercus suber, showing the thick spongy bark used for making wine bottle corks
- Kashiwa-mochi.jpg
Kashiwa-mochi rice cake wrapped in oak leaf, Japan
ConservationEdit
An estimated 31% of the world's oak species are threatened with extinction, while 41% of oak species are considered to be of conservation concern. The countries with the highest numbers of threatened oak species (as of 2020) are China with 36 species, Mexico with 32 species, Vietnam with 20 species, and the US with 16 species. Leading causes are climate change and invasive pests in the US, and deforestation and urbanization in Asia.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Template:Citation</ref> In the Himalayan region of India, oak forests are being invaded by pine trees due to global warming. The associated pine forest species may cross frontiers and integrate into the oak forests.<ref>Kala, C.P. (2012). Biodiversity, communities and climate change. Teri Publications, New Delhi, Template:ISBN.</ref> Over the past 200 years, large areas of oak forest in the highlands of Mexico, Central America, and the northern Andes have been cleared for coffee plantations and cattle ranching. There is a continuing threat to these forests from exploitation for timber, fuelwood, and charcoal.<ref>Kappelle, M. (2006). "Neotropical montane oak forests: overview and outlook", pp 449–467 in: Kappelle, M. (ed.). Ecology and conservation of neotropical montane oak forests. Ecological Studies No. 185. Springer-Verlag, Berlin, {{#invoke:doi|main}} Template:ISBN.</ref> In the US, entire oak ecosystems have declined due to a combination of factors thought to include fire suppression, increased consumption of acorns by growing mammal populations, herbivory of seedlings, and introduced pests.<ref>Lorimer, C.G. (2003) Editorial: The decline of oak forests Template:Webarchive. American Institute of Biological Sciences.</ref> However, disturbance-tolerant oaks may have benefited from grazers like bison, and suffered when the bison were removed following European colonization.<ref name="Hitchmough Vera 2002">Template:Cite journal</ref><ref>Template:Cite book</ref>
CultureEdit
SymbolsEdit
The oak is a widely used symbol of strength and endurance.<ref name="Leroy Plomion Kremer 2019">Template:Cite journal</ref> It is the national tree of many countries,<ref name="Venables 2012"/> including the US,<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Bulgaria, Croatia, Cyprus (golden oak), Estonia, France, Germany, Moldova, Jordan, Latvia, Lithuania, Poland, Romania, Serbia, and Wales.<ref name="Venables 2012">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Ireland's fifth-largest city, Derry, is named for the tree, from Template:Irish place name.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Oak branches are displayed on some German coins, both of the former Deutsche Mark and the euro.<ref>Template:Cite book</ref> Oak leaves symbolize rank in armed forces including those of the United States. Arrangements of oak leaves, acorns, and sprigs indicate different branches of the United States Navy staff corps officers.<ref name="Websters Online Dictionary">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The oak tree is used as a symbol by several political parties and organisations. It is the symbol of the Conservative Party in the United Kingdom,<ref>Template:Cite news</ref> and formerly of the Progressive Democrats in Ireland.<ref name=r9>Coalition Government 1989 To 1992. progressivedemocrats.ie</ref>
ReligionEdit
The prehistoric Indo-European tribes worshipped the oak and connected it with a thunder god, and this tradition descended to many classical cultures. In Greek mythology, the oak is the tree sacred to Zeus, king of the gods. In Zeus's oracle in Dodona, Epirus, the sacred oak was the centerpiece of the precinct, and the priests would divine the pronouncements of the god by interpreting the rustling of the oak's leaves.<ref>Frazer, James George (1922). The Golden Bough. Chapter XV: The Worship of the Oak. Template:Webarchive</ref> Mortals who destroyed such trees were said to be punished by the gods since the ancient Greeks believed beings called hamadryads inhabited them.<ref name="Bell1790">Template:Cite book</ref> In Norse and Baltic mythology, the oak was sacred to the thunder gods Thor and Perkūnas respectively.<ref>Template:Cite book</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> In Celtic polytheism, the name druid, Celtic priest, is connected to Proto-Indo-European *deru, meaning oak or tree.<ref name=Credo>Template:Cite book</ref> Veneration of the oak survives in Serbian Orthodox Church tradition. Christmas celebrations include the badnjak, a branch taken from a young and straight oak ceremonially felled early on Christmas Eve morning, similar to a yule log.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
HistoryEdit
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- Category: Individual oak trees
Several oak trees hold cultural importance; such as the Royal Oak in Britain,<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> the Charter Oak in the United States,<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> and the Guernica oak in the Basque Country.<ref name="ElMundoTrees">Template:Cite news</ref> "The Proscribed Royalist, 1651", a famous painting by John Everett Millais, depicts a Royalist hiding in an oak tree while fleeing from Cromwell's forces.<ref>Arborecology, containing a photograph of the Millais oak Template:Webarchive. arborecology.co.uk</ref><ref>Millais, J. G. (1899) Life and Letters of Sir John Everett Millais, vol. 1, p. 166, London : Methuen.</ref>
In the Roman Republic, a crown of oak leaves was given to those who had saved the life of a citizen in battle; it was called the "Civic Crown".<ref name="Credo"/> In his 17th century poem The Garden, Andrew Marvell critiqued the desire to be awarded such a leafy crown: "How vainly men themselves amaze / To win the palm, the oak, or bays; And their uncessant labors see / Crowned from some single herb or tree, ..."<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Template:Cite journal</ref>
NotesEdit
ReferencesEdit
Further readingEdit
- Byfield, Liz (1990) An Oak Tree, Collins Book Bus, London: Collins Educational, Template:ISBN
- Phillips, Roger (1979). Trees of North America and Europe, Random House, New York Template:ISBN.
- Logan, William B. (2005) Oak: The Frame of Civilization, New York; London: W. W. Norton, Template:ISBN
- Paterson, R. T. (1993). Use of Trees by Livestock, 5: Quercus, Chatham: Natural Resources Institute, Template:ISBN
- Royston, Angela (2000). Life Cycle of an Oak Tree, Heinemann first library, Oxford: Heinemann Library, Template:ISBN
- Savage, Stephen (1994). Oak Tree, Observing nature series, Hove: Wayland, Template:ISBN
- Tansley, Arthur G. (1952). Oaks and Oak Woods, Field study books, London: Methuen. Template:OCLC.
- Żukow-Karczewski, Marek (1988). "Dąb – król polskich drzew" ("Oak – the king of the Polish trees"), AURA: A Monthly for the Protection and Shaping of Human Environment, 9, 20–21.
External linksEdit
Template:Sister project Template:Sister project
- Flora of China – Cyclobalanopsis
- Oak diseases
- Flora Europaea: Quercus
- Common Oaks of Florida
- Oaks of the world
- The Global Trees Campaign The Red List of Oaks and Global Survey of Threatened Quercus
- Template:Cite EB1911
Template:Culinary wrappings Template:Tannin source Template:Woodworking Template:Taxonbar Template:Authority control