Oak trees


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Oak trees
English oak (Quercus robur), illustration

English oak ( Quercus robur ), illustration

Systematics
Nuclear eudicotyledons
Rosids
Eurosiden I
Order : Beech-like (Fagales)
Family : Beech family (Fagaceae)
Genre : Oak trees
Scientific name
Quercus
L.

The oaks ( Quercus ) are a genus of plants in the beech family (Fagaceae).

A large oak tree in Alabama

description

Inflorescences of Quercus petraea
Acorn with cupula of Quercus ithaburensis subsp. macrolepis

Vegetative characteristics

Oak species are deciduous or evergreen trees , and more rarely shrubs .

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).

Generative characteristics

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.

ecology

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 ).

Oak species are feeding habitats for the caterpillars of many butterfly species . In Central Europe it is only surpassed by the Salweide . Both are home to over 100 species.

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

Quercus section : Portuguese oak ( Quercus faginea )
Section Quercus : Large-fruited oak ( Quercus macrocarpa ) - fruits (with leaves)
Lobatae section : water oak ( Quercus nigra )
Lobatae section : swamp oak ( Quercus palustris )
Lobatae section : Red oak ( Quercus rubra )
Section Ponticae : Armenian oak ( Quercus pontica )
Virentes section : Virginia oak ( Quercus virginiana )
Cerris section : cork oak ( Quercus suber )
Cerris section : Macedonian oak ( Quercus trojana )
Cyclobalanopsis Section : Bamboo-leaved Oak ( Quercus myrsinifolia )
Ilex section : Kermes oak ( Quercus coccifera )

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
  • 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.

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:
    • Alder-leaved oak ( Quercus alnifolia Poech )
    • Kermes oak ( Quercus coccifera L. , incl.Quercus calliprinos Webb )
    • Holm oak ( Quercus ilex L. )
    • Quercus rotundifolia Lam. : Also referred to as the subspecies Quercus ilex subsp. rotundifolia (Lam.) O.Schwarz ex Tab.Morais of the holm oak viewed.

Information on the species commonly found in Central Europe

Harvesting and planting acorns: a short video from Wales.

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.

For red oak , originally native to eastern North America and planted in the temperate areas , see main article .

Culture

religion

In the ancient religions , myths and legends , the oak was a sacred tree. She was often associated with lightning gods or god princes.

  • 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.

Law

  • Because of the religious significance, court was held under the oaks (as well as under linden trees) ( court trees , for example Femeiche ).

symbolism

Oaks and acorns are also often used in coats of arms . Here Kirchardt's municipal
coat of arms .
The oak tree can be found in the coat of arms of the city of Berga / Elster .
Oak branch - back of the last German penny pieces
  • Symbol for eternity (an oak life lasts 30 generations)
  • "Oak tree"
    • Germany: typical German heraldic tree since the 18th century; in particular the German national tree promoted by Klopstock
    • Great Britain
    • United States
  • " Double oak "
    • Symbol for the unity of Schleswig-Holstein . In many villages in the country, double oaks, i.e. two-stemmed oaks, were planted around 1900. The Schleswig-Holstein song says: Expensive land, you double oak, under one roof.
Anti -reprocessing plant Wackersdorf memorial plaque in Pfreimd
  • 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.

Songs

  • 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.
Branch of an oak in cross section
Beam sample from the town hall of Gödenroth (oak wood)
Close-up of oak cross-section
Wood of bog oak
Wood of the grape oak
Heavy oak door in Basel

Others

use

Oak wood

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 .

Bog oak

Bog oaks in the Burg (Dithmarschen) nature experience area at the Forest Museum
Information on the age of these tribes

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.

Acorns

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 .

Starch grains in an acorn of the red oak
(micrograph in polarized light)

Acorn malt is suitable for making beer .

bark

Tannins for tannery were obtained from the young, smooth bark (oak peeling forest).

The bark of the cork oak ( Quercus suber ) is used as a cork to make corks , cork floors and more.

In folk medicine, barkless oak bark was used to heal inflammation of the mucous membranes.

Gallen

From the gall apples (knoppers), which are caused by the common oak gall wasp, document- proof iron gall ink was extracted or used for dyeing and tanning.

Fruit cups

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.

The tannins and aldehydes contained in oak wood can cause allergic reactions ( rhinitis , asthma ) when inhaled .

Well-known oaks

Bühleiche in Plochingen -Stumpenhof
Avenue of oaks
Oak as a natural monument - oak in the Kreuzwiese in Engelrod

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:

See also

swell

further reading

  • T. Denk, GW Grimm, PS Manos, M. Deng, AL Hipp: An Updated Infrageneric Classification of the Oaks: Review of Previous Taxonomic Schemes and Synthesis of Evolutionary Patterns. Oaks Physiological Ecology. Exploring the Functional Diversity of Genus Quercus L. Springer International Publishing, 2017.
  • Joachim Krahl-Urban: The oaks. Forest monograph of the sessile oak and the English oak. Parey, Hamburg 1959.
  • Wolf Dieter Becker: Of charred food supplies, mysterious walls and bitter meals - archaeobotanical investigations in Westphalia. (P. 191–194) In: A country makes history Archeology in North Rhine-Westphalia. Cologne 1995, ISBN 3-8053-1801-4 .

Web links

Wiktionary: Oak  - explanations of meanings, word origins, synonyms, translations
Commons : Oak trees ( Quercus )  - Collection of images, videos and audio files

Individual evidence

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