English oak ( Quercus robur ), illustration
The alternate leaves arranged in a spiral on the branches are usually divided into a petiole and a leaf blade. The thin to leathery, simple leaf blades are lobed or unlobed. The leaf margins are smooth or serrated to spiky serrated. The inconspicuous, extrapetiolaren stipules falling early on (for Quercus sadleriana they are conspicuous).
Oak species are monoecious, mixed sexes ( monoecious ). The inflorescences , usually in groups of several at the base of young branches, are unisexual. The flowers are very simply built, as is often the case with wind-pollinated ( anemophilic ) taxa . The male flowers are grouped in hanging inflorescences (catkins). The bracts are fused. The male flowers usually contain six (two to twelve) stamens , there are sometimes reduced pistillodes (sterile pistils) in the form of tufts of hair. The female flowers usually contain three (to six) carpels and a pistil with several styles. Each cupula (fruit cup, cone) contains only one female flower.
Oaks are particularly recognizable by their fruit , the acorn, and can be distinguished in the individual species. The acorn is a nut fruit . They ripen in the first or second year after pollination. Each nut fruit is surrounded by a fruit cup.
The basic chromosome number is x = 12.
People have noticed from ancient times that oaks are home to an unusual variety of insects (up to 1000 species in a crown). The specialization of numerous insect species on Quercus species is considered a sign of the great developmental age ( coevolution ).
Locations of the oak species in Central Europe
In Germany , according to the Third National Forest Inventory (2012), oaks make up 11.6 percent of the forest area with an area of 1.1 million hectares. The oak area in German forests increased by 70,000 hectares between 2002 and 2012. The oaks are the second most common deciduous tree genus in Germany after the common beech . These are mainly the native oak species common oak and sessile oak . The red oak , imported from North America, occupies only 0.5 percent with an area of 55,000 hectares.
Oak species already appeared in the Tertiary . They are found in fossil form twelve million years ago, for example in sediments in the Lower Rhine Bay . The star hair , which is very common in the Oligocene / Eocene Baltic amber , is also attributed to oaks. Oak blossoms are also not uncommon in Baltic amber. Oaks are very well documented by fossil pollen (e.g. from the Miocene of Austria, Iceland, and the Eocene of Greenland and the United States), which can be assigned to certain sections or evolutionary lines due to their ornamentation. From the spread of fossil pollen and the molecular clocks based on it, it can be concluded that today's main lineages of the oaks emerged and diversified in the lower Eocene. In the Paleocene of Greenland and the Upper Cretaceous of the United States, a wide variety of pollen from both extinct and still living Fagaceae (beech family) could be detected, but oaks are missing. The assignment of some Cretaceous plant fossils to Quercus or Quercophyllum is, however, controversial.
Systematics and distribution
The Roman author Quintus Ennius (239–169 BC) has the earliest literary evidence for the Latin name of a Quercus species, 'quercus'.
Quercus species are found in North America , Mexico , the Caribbean Islands , Central America , in South America only in Colombia , in Eurasia and in North Africa . Quercus is the most important genus of deciduous trees in the northern hemisphere . One focus of biodiversity is North America.
The genus Quercus contains around 400 to 600 species (461, as of 2020), of which at least 280 are in the subgenus Quercus and at least 140 in the subgenus Cerris . The genus is divided into the (primarily) New World sub-genus Quercus (maximum diversity in North and Central America, ~ 30 species in Europe and Asia) with five sections, Quercus (white oak in the narrower sense) , Lobatae (red oak) , Ponticae, Protobalanus and Virentes ( Engl. Live oaks ), and the ancient genus Cerris with three sections, Cerris (Zerreich in the narrower sense), Cyclobalanopsis and Ilex , divided. The classic division into two sub-genera (or genera), going back to Andres Sandø Ørsted , Cyclobalanopsis (section Cyclobalanopsis ) and Quercus (all other oaks) found no equivalent in molecular-phylogenetic family trees.
A complete list of species with information on distribution can be found in R. Govaerts. Here is a selection of species:
Subgenus Quercus L.
- Section Quercus ; Synonyms: (Eu-) Lepidobalanus , Leucobalanus, Mesobalanus ; White oak ; Occurrence: Europe, Asia, North Africa, North America
- American white oak ( Quercus alba L. )
- Oriental white oak ( Quercus aliena flower ): It occurs in five varieties from Japan to Indochina.
- Arizona oak ( Quercus arizonica coffin. )
- Two-tone oak ( Quercus bicolor Willd. )
- Algerian oak ( Quercus canariensis Willd. ): It is found in Morocco, Algeria, Tunisia, southern Portugal and Spain.
- Japanese emperor oak ( Quercus dentata Thunb. )
- Blue oak ( Quercus douglasii Hook. & Arn. )
- Quercus engelmannii Greene : It occurs in southern California and northern Baja California (Mexico).
- Portuguese oak ( Quercus faginea Lam. ): There are three subspecies. It occurs in Morocco, Portugal, Spain and the Balearic Islands.
- Hungarian oak ( Quercus frainetto tenore )
- Gambel oak ( Quercus gambelii Nutt. ): Found in the western, central, and southern United States to northern Mexico.
- Oregon oak ( Quercus garryana Douglas ex Hook. )
- Gall oak ( Quercus infectoria Olivier ): It occurs from Greece to southwestern Iran. There are two subspecies.
- Quercus lanata Sm .: It occurs in the Himalayan region as well as in southern and southeastern Asia.
- Californian white oak ( Quercus lobata Née )
- Lyre-leaved oak ( Quercus lyrata Walt. )
- Large-fruited oak ( Quercus macrocarpa Michx. ): It occurs in two varieties from southern Canada to Alabama .
- Persian oak ( Quercus macranthera Fischer & CAMey. )
- Basket Oak ( Quercus michauxii Nutt. )
- Mongolian oak ( Quercus mongolica Fisch. Ex Turcz. )
- Chestnut oak ( Quercus montana Willd. )
- Yellow oak ( Quercus muehlenbergii Engelm. )
- Sessile oak ( Quercus petraea (Mattuschka) Liebl. )
- Pyrenean oak ( Quercus pyrenaica Willd. )
- Downy oak ( Quercus pubescens Willd. )
- English oak or German oak ( Quercus robur L. ):
- Quercus stellata Wangenh. : Found in nine varieties in the eastern and southeastern United States.
- Section Lobatae Loudon ; Synonym: erythrobalanus ; Red oak ; Occurrence: North, Central and South America:
- Quercus acerifolia (EJPalmer) Stoynoff & Hess : It occurs in Arkansas .
- Californian holm oak ( Quercus agrifolia ) Née : It occurs from western California to Baja California Norte , Mexico .
- Quercus arkansana coffin. : It occurs in eastern Texas, Arkansas , Louisiana , Alabama , Georgia , northwest Florida, and maybe Mississippi .
- Quercus buckleyi Nixon & Dorr : It occurs in the US states of Oklahoma and Texas.
- Quercus canbyi Trel. (Syn .: Quercus graciliformis C.H.Mull. ): It occurs from Texas to northeast Mexico.
- Scarlet Oak ( Quercus coccinea Münchh. )
- Quercus ellipsoidalis E.J. Hill : It occurs in the United States and southwestern Ontario .
- Quercus emoryi Torr. : It occurs from Arizona to western Texas and northern Mexico.
- Sickle-leaved oak ( Quercus falcata Michx. )
- Quercus georgiana M.A. Curtis : It comes in the US states of Georgia , Alabama , North Carolina and used to be in South Carolina .
- Quercus gravesii Sudw. : It occurs from southwest Texas to the Mexican state of Coahuila .
- Quercus hemisphaerica W. Bartram ex Willd. : It occurs from the southeastern United States to Texas.
- Mexican willow oak ( Quercus hypoleucoides A.Camus ): It occurs in the southwestern United States and northwestern Mexico.
- Bush oak ( Quercus ilicifolia Wangenh. )
- Shingle oak ( Quercus imbricaria Michx. )
- Quercus incana W. Bartram : It occurs from the southeastern United States to Oklahoma and Texas.
- Quercus inopina Ashe : It occurs in Florida.
- California black oak ( Quercus kelloggii Newb. )
- Fork oak ( Quercus laevis Walt. ): It is found in the southeastern United States.
- Quercus laurifolia Michx. : It occurs from the southeastern United States to Oklahoma and Texas.
- Black oak ( Quercus marilandica Muenchh. )
- Myrtle-leaved oak ( Quercus myrtifolia flower ): It is found in the southeastern United States.
- Water oak ( Quercus nigra L. ): It is found in the central and eastern United States.
- Quercus pagoda Raf. : It occurs in the eastern, southeastern, and central United States.
- Swamp oak ( Quercus palustris Münchh. )
- Quercus parvula Greene : On Santa Cruz Island and on the California coast.
- Quercus phellos L.
- Quercus pumila Walter : It is found in the southeastern United States.
- Quercus robusta C.H. Mull. : This endemic occurs only in the Chisos Mountains in Texas.
- Red oak ( Quercus rubra L. )
- Shumard's Oak ( Quercus shumardii Buckl. ): It occurs in three varieties in the central and eastern United States and in southern Ontario .
- Quercus tardifolia C.H. Mull . : It occurs from the Chisos Mountains in Texas to the Mexican state of Coahuila .
- Quercus texana Buckley : It is found in the central and southeastern United States.
- Dyer's oak ( Quercus velutina Lam. )
- Quercus viminea Trel. : It occurs in northern and western Mexico and southern Arizona .
- Quercus wislizeni A. DC. : It occurs in two varieties in California and in the Mexican state of Baja California Norte .
- Section Protobalanus (Trel.) O.Schwarz : With about five species; Occurrence: Southwestern United States, Northwestern Mexico:
- Quercus chrysolepis Liebmann
- Quercus palmeri Engelmann : It occurs in southern California, in Arizona and in Mexico in northern Baja California .
- Quercus tomentella Engelmann : It occurs on the Californian Channel Islands , in the Mexican state of Baja California and on the island of Guadalupe .
- Quercus vacciniifolia Kellogg ex Curran : It occurs in the US states of southwestern Oregon , western Nevada and California.
- Section Ponticae Stefanoff , one species each in Europe (Caucasus) and in western North America (Oregon, California):
- Virentes Loudon Section : Seven Species; Occurrence: Southeastern United States, Mexico to Costa Rica, Cuba.
- Quercus brandegeei Goldman : It occurs in northern Mexico.
- Quercus cubana A.Rich. (Syn .: Quercus sagraeana Nutt. ): It occurs in western Cuba.
- Quercus geminata Small : It is found in the southeastern United States.
- Quercus fusiformis Small : It occurs from southwest Oklahoma to northeast Mexico.
- Quercus minima (coffin) Small : Found in the southeastern United States.
- Quercus oleoides Schltdl. & Cham. : It occurs from Mexico to Costa Rica.
- Virginia oak or living oak ( Quercus virginiana Mill. )
Subgenus Cerris Oerst.
- Section Cerris Loudon ; Distorted oaks ; Occurrence: Europe, North Africa, Asia:
- Japanese chestnut oak , also "sawn oak" or "silkworm oak" ( Quercus acutissima Carruth. )
- Chestnut-leaved oak ( Quercus castaneifolia C.A. Meyer )
- Zerr oak ( Quercus cerris L. )
Quercus ithaburensis Decne. With two subspecies:
- Quercus ithaburensis subsp. ithaburensis : It occurs from central and southern Turkey to northwestern Jordan.
- Quercus ithaburensis subsp. macrolepis (Kotschy) Hedge & Yalt. (Syn .: Quercus macrolepis Kotschy ): It occurs in southeastern Italy and from the Balkan Peninsula to Syria.
- Lebanon oak ( Quercus libani Olivier )
- Cork oak ( Quercus suber L. )
- Macedonian oak ( Quercus trojana Webb )
- Chinese cork oak ( Quercus variabilis flower )
- Section Cyclobalanopsis (Oerst.) Benth. & Hook.f ; Occurrence: Asia:
- Evergreen Japanese oak , also called Japanese red oak ( Quercus acuta Thunb. ): It is found in Japan, southern Korea, Taiwan and China.
- Blue Japanese oak ( Quercus glauca Thunb. ): It occurs from the Himalayas to Japan.
- Kerr oak ( Quercus kerrii Craib ): It occurs from southeastern Bangladesh to Hainan .
- Bamboo-leaved oak , also called Japanese white oak ( Quercus myrsinifolia flower ): It occurs in Japan, in Korea and from China to Indochina.
- Section Ilex Loudon ; Synonym: heterobalanus ; Occurrence: North Africa, Europe, Asia:
Information on the species commonly found in Central Europe
The English oak and sessile oak , native to Central Europe, are typical species of white oak, although these two species occur together in large areas and tend to hybridize , and therefore often cannot be clearly differentiated. They are so-called light tree species, which means that they need more light as they grow than the European beech and form open, light crowns themselves. The use of forests for forest pasture ( Hutewald ) has therefore promoted the formation of oak forests, because the grazing animals have inhibited the offspring of the European beech, as it is less able to cope with browsing and has less ability to move. The core wood of the white oak is very durable and was used a lot in shipbuilding . The two species native to Central Europe provide a habitat for well over 500 insect species. For more information, see the main articles of these two types.
- Christianity : The oak was considered a tree of life, it stood in its permanent wood and the long life of the tree for eternal life and eternal salvation. The tree was also associated with the faithful Saint Mary. The oak can be found in the Gothic and early modern times on biblical covers.
- Ancient Greece : consecrated to Zeus by the Greeks (oak oracle of Dodona )
- Rome : consecrated to Jupiter by the Romans ,
- Celts : Dedicated to the sky ruler and weather god Taranis . The Roman historian Pliny the Elder tells us that the Celts did not perform any ritual acts without oak leaves. According to one derivation, the word druid for priest could be derived from the mainland Celtic root dru .
- Teutons : consecrated to the storm god Donar (= Thor). According to legend, St. Boniface (apostle of the Germans) felled the Donariche near Geismar in 723 to prove to the heathen to be converted that their God was an impotent being who could not even protect his tree.
- Because of the religious significance, court was held under the oaks (as well as under linden trees) ( court trees , for example Femeiche ).
- Symbol for eternity (an oak life lasts 30 generations)
- "Oak tree"
- " Double oak "
- " Oak leaves "
- Ornament in the Gothic
- Part of military rank or badges of honor :
- Part of German coins
- "Oak wreath"
- "Peace Oak"
- Peace oaks were planted as symbols in many places in Germany, especially after the Franco-Prussian War of 1870–1871.
- Resistance oak
- " Olympic oak "
- On the occasion of the award ceremony for the gold medal winners at the Summer Olympics in 1936 , an oak seedling in a clay pot with the inscription " Waxes to honor the victory - calls for further action " was presented.
- The oak is also of outstanding importance in German songs, for example in the Lower Saxony song : "(...) As solid as our oaks, we always withstand when storms roar over the German fatherland."
- In the album Baumlieder, songwriter Roland Zoss sings about the trees, a. a. the oak and its inhabitants.
- The vernacular suggests that oaks are struck by lightning more often than other trees (“oaks should give way, beeches should look for”). This statement is untrue, see also the article on lightning, section “Behavior in thunderstorms” .
- The artist Joseph Beuys presented the work “ 7000 Eichen ” in Kassel at documenta 7 .
- The oak is the tree of the year 2016 in Austria.
Oak trunks have the gray-brownish heartwood in their middle , which gets the typical sour-spicy oak smell from the stored tannic acid ; The sapwood is two to five centimeters light-colored, young wood that is still sap-infused towards the bark and sharply demarcated . The wood of the stem and has a bulk density at Traubeneiche Darrfeuchte (p0) 0.39 to 0.93 g / cm³, an average of 0.65 g / cm³, it is hard and easy to split.
Further technical data:
- Modulus of elasticity from bending test E: 13,000 N / mm²,
- Tensile strength along Sigma ZB: 110 N / mm²,
- Compressive strength along Sigma DB: 52 N / mm²,
- Flexural strength along Sigma BB: 95 N / mm²,
- Impact energy at break Omega 60-75 kJ / m²,
- Brinell hardness: lengthways 64–66 N / mm², crossways 34–41 N / mm²
The valuable hardwood from well-grown trunks is preferably processed into veneers. Heartwood is highly resistant to rotting and is rarely attacked by worms. Splint on the other hand very quickly. Oak is used for furniture, stairs, floors, exterior doors and windows, half-timbering and in hydraulic engineering. Of all types of oak, only about 180 are suitable for making wine barrels, see also barriques .
Oak is also considered to be good firewood with little flying sparks. However, its flame pattern is not as beautiful as with beech and birch wood or with fruit wood ; In addition, the calorific value is slightly lower than that of the European beech .
A special feature of the bog oak . These are not about a tree species, but about oak logs that had lain for centuries in bogs, swamps or river banks and were excavated. The tannic acid of the oak combines with the iron salts of the water, which makes the wood very hard and discolored. The discoloration can be very irregular and varies from light gray to dark yellow, dark brown, blue-gray to deep black. These subfossil oaks can be 600 to 8500 years old.
The fruits (acorns) are rich in carbohydrates and proteins and were used to fatten acorns . The pigs were driven to pasture in the woods, which were often operated as middle forest . Acorns were used by humans as food in prehistoric and early historical times as well as in times of need. Acorns were regularly used as a staple food by North American Indians (e.g. the Maidu ).
For use as food, the peeled and crushed acorns have to be gradually freed from the water-soluble tannins by bathing them several times in water , which can be easily recognized by the lack of discoloration of the water, with a higher temperature accelerating the process. They contain high amounts of tannins . Then they can be used, for example, as a flour substitute for porridge and cakes or as a coffee substitute " Muckefuck ", whereby with the latter use the tannic acid can optionally not or not completely be removed, for example for medical reasons. In Korea , the raw acorn paste is made into dotori-muk ( 도토리묵 ), an oak jelly , one form of which is dotori-muk muchim ( 도토리묵 무침 ), and oak noodles are also made; a Korean form is Dotori-guksu ( 도토리 국수 ), in Japan there are similar ones .
Tannins for tannery were obtained from the young, smooth bark (oak peeling forest).
In folk medicine, barkless oak bark was used to heal inflammation of the mucous membranes.
The fruit cups of some species (including Valons) were used for tanning in the past.
Medicine and pharmacology
All parts of the oak are slightly poisonous because of the tannins they contain and can lead to gastrointestinal symptoms (gastrointestinal irritation, vomiting, diarrhea) (see the article: List of poisonous plants ). However , oak was and is valued as a medicinal plant . The oak mistletoe , which up until the Middle Ages was thought to be the fruit of oak, also found magical and therapeutic uses.
Oak specimens, which are known due to their thickness, can be looked up in two lists:
In addition, other oaks are listed here.
The thickness of an oak is also often used to estimate the age of an oak. Another method is an estimate based on historical records. Since the oldest wood from the center of the trunk is missing, neither annual ring counting nor radiocarbon dating is possible.
The oldest oak in Germany is said to be the Femeiche in Raesfeld-Erle in the Borken district , whose age is estimated at 600 - 850 years due to its thickness. Three specimens are possible for the oldest oak in Europe, as the age estimates are very imprecise. The 1000-year-old oak in Bad Blumau ( Eastern Styria ) is estimated to be over 1200 years old, the English oak in Bulgaria in Granit, Stara Zagora district at 1640 years and the royal oak in Denmark in the Jægerspris Nordskov nature reserve on the Hornsherred peninsula between 1400 and 2000 years estimated.
Other well-known oaks:
- Begging oak in the Hainich National Park : 600 to 800-year-old oak with a height of 13 meters, a circumference of 5.6 meters and a split trunk
- Flowering oak in Ratekau
- Bridegroom oak in Dodau near Eutin
- Thick oak (Eisenach) in Berteroda : 1000-year-old pedunculate oak circumference 9.62 meters and 16 meters high
- Chełmoński Oak , Radziejowice (Masovian Voivodeship) Poland
- Donareiche in Fritzlar (Northern Hesse)
- Seven Brothers Oak in Friesack (Brandenburg)
- Count oak in Harsum-Asel, Lower Saxony, age around 1000 years.
- Border whale corpses on the Limes
- Guardian of the field near Lichtenfels (Upper Franconia) (approx. 1000 years)
- Imperial empires
- Linden oak , North Bethesda, Maryland, United States
- Luther oaks
- Olympic oaks
- Pomeranian Grenzmal-Eiche near Lutzig ( Stare Ludzicko ) in Western Pomerania ; Trunk circumference (1924) 9.5 meters
- Russian oak
- Sokół oak in Poland
- Collegiate court oak in Bassum , trunk circumference 5.05 meters, height 23 meters
- Hour oak near Ludwigsfelde (Brandenburg),
- Gypsy oaks in Poland
- Foloi (Peloponnese) , oak forest
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