Quercus suber

Cork oak ( Quercus suber)

The cork oak ( Quercus suber) is an evergreen deciduous tree of the western Mediterranean from the kind of oaks (Quercus ). It bears drought and provides low demands on the soil. In Central Europe it is not hardy. The name derives from the mighty cork layers of the tribe, which are used for cork extraction. A single tree can provide during its life 100 up to 200 kg cork. Cork oak forests are home to a large number of animal and plant species. Since cork is replaced as a bottle closure increasingly by other materials, these forests are at risk as part of the cultural landscape and thus threatened species such as the Iberian Lynx from extinction.

• 3.1 symbiosis
• 3.2 Diseases and predators

• 7.1 Literature
• 7.2 Notes and references

Description

Appearance and a hard place

The cork oak grows as evergreen tree which reaches an average height 10-20 meters, or in rare cases up to 25 meters and trunk diameter ( DBH ) of 50 to 90 centimeters. It forms a dense and asymmetric -faceted at a height of two to three meters crown that spreads far in free-standing trees. The crown can be divided into a number of mutually remote, round partial crowns.

The young branches are densely hairy pale gray or whitish. Older branches are strong and knotty. Mature trees only form short shoots with lengths of 7-15 inches.

Characteristic of the cork oak are the thick, longitudinally fissured cork layers of gray-brown Stammborke. The cambium of the smooth in young trees bark forms very early a cork layer, which can be three to five inches thick. The light and spongy cork tissue shows vertical cracks and is white on the outside, red on the inside reddish brown to. After the cork harvest the stem appears reddish brown, later, however, significantly darker. The wood is ring-porous, has a brown heartwood and a light reddish sapwood. The cork oak develops a taproot that reaches a depth of one to two meters, and long from several meters horizontally extending lateral roots originate. The trees are over 400 years old, beer tete copies are 150 to 200 years old.

The leathery leaves are alternate and are 3-5 inches long and 1.5 to 4 centimeters wide. The shape varies from round, oval and lanceolate - oval. The leaf blade has on both edges of five to seven sharp teeth and a pointed growing tip (apex). The midrib occurs on the lower leaf surface is clear, the lateral nerves of first order usually lead to the teeth of the blade edge. The upper leaf surface is bright green, the leaf underside whitish hairs and dense. In young trees, the hair is missing. The leaf stalks are 6 to 18 millimeters long and are also hairy. At the base of the petiole are two narrow lanceolate, five millimeters long and bright red stipules that fall in the first year. The new leaves appear in April and May, in which older leaves are shed. They usually stay for two to three years on the tree, rarely only one year, the latter especially in tough environmental conditions and on the northern border of the range. Extremely cold winter can also lead to complete defoliation.

Inflorescence and flower

The cork oak is monoecious getrenntgeschlechtig ( monoecious ), enter it in both female and male flowers on a copy on. The female flowers form upright inflorescences in the leaf axils of young branches. These are made from a 5 to 30 mm long, hairy shaft with two to five separate petals. The female flowers contain a small, hairy, four - to six - zipfelige perianth and three to four pencils. The male catkins also occur at the leaf axils of young branches. They are bright red at the beginning and stand upright, older kittens are yellow and hanging, four to seven inches long and have a whitish hairy axis. The individual flowers are sessile and have a hairy outer perianth, which is colored red when opened. The four to six stamens are whitish with yellow, egg-shaped anthers. They are longer than the bracts.

Weathered trunk cross -section, the cork is light gray, the master dark

Cork sheet: front and rear

Acorn with fruit cup

Fruit stand, fruit and seed

The seed heads are 0.5 to 4 inches long and carry two to eight acorns. The fruits are included about half of the fruit cup ( cupula ), fruit cups have a diameter of 2 to 2.5 inches. The upper scales of the cupula are gray and hairy, with the subspecies Quercus suber occidentalis the scales are close together or are fused. The size of acorns varies between lengths of 2 to 4.5 inches, and diameters from 1 to 1.8 inches. The fruit body ( pericarp ) is bald, smooth and shiny brownish red. The hilus ( the point of attachment of the seed ) is convex and has a diameter of six to eight millimeters.

Chromosome number

The chromosome number is 2n = 24

Distribution and habitat requirements

The distribution area of the cork oak is the space around the western Mediterranean basin. In Portugal, natural and planted stocks cover an area of 750,000 hectares. Natural resources of the nominate there are at altitudes between 150 and 300 meters above sea level, the subspecies occidentalis can be found along the Atlantic coast. In Spain, the incidence remain mostly below 600 meters in altitude, but rarely reach heights of 1200 meters also. In central Spain, cork oaks are rare. In Italy you will find natural occurrence along the Tyrrhenian Sea and in the eastern Apulia on the Adriatic. Also on the Adriatic, there is the cork on the Dalmatian coast. In Sardinia it is one of the most common forest trees. Natural and man-made resources exist in Africa on the Mediterranean coast of Tunisia, Algeria and Morocco, and at altitudes up to 1000 meters, at High Atlas mountains up to 2000 meters. Outside the natural range the cork tree is cultivated in the Crimea, the Caucasus, India and the U.S. Southwest. The subspecies Quercus suber occidentalis also thrives in mild areas of England.

The species is very light demanding and can not survive in dense stands. It is heat -loving, growing at an annual average temperatures 13-17 ° C and withstands temperatures up to 40 ° C. Maximum In the area of ​​distribution, the temperature falls rarely below freezing, but it will tolerate temperatures down to -5 ° C without damage and to -10 ° C without major damage. The cork oak is not hardy in Central Europe. It bears drought and survived summer droughts by reducing the metabolism. An annual rainfall of 500 to 700 millimeters is considered optimal, on cooler locations can with sufficient air humidity 400 to 450 millimeters suffice. Cork oaks provide low soil requirements and grow on poor, dry or rocky sites. They thrive hardly on calcareous soils, but they are often found on crystalline schists, gneiss, granite, and sands. The acidity of the soil should be between pH 4.5 and 7.

Ecology

In natural populations, the cork oak grows together with the holm oak (Quercus ilex), the downy oak (Quercus pubescens), the maritime pine (Pinus pinaster ), the pine (Pinus pinea), the Western Strawberry Tree (Arbutus unedo ) and the olive tree ( Olea europaea), sativa in cooler areas with the chestnut ( Castanea ). In addition to these tree species are used as shrub -forming species, the Kermes oak (Quercus coccifera ), Holly buckthorn ( Rhamnus alaternus ), species of the genus phillyrea, the myrtle ( Myrtus communis), the heath -Art Erica scoparia, the Rough sarsaparilla ( Smilax aspera ) and the Montpellier Rockrose (Cistus monspeliensis ) frequently occur in combination with the cork oak. Cork oak forests are home to several rare species, as in the Iberian Peninsula for the endangered Iberian lynx (Lynx pardinus ) and the endangered Spanish imperial eagle (Aquila adalberti ), also wintered here, much of the European crane population. In the cork oak forests of Tunisia Barbary red deer lives (Cervus elaphus subsp. Barbarus ).

Symbiosis

The cork comes with several types of fungi a mycorrhizal symbiosis. Here, the fine root system of the oak is in close contact with the mycelium of the fungus. The oak is replaced by the mushroom water and nutrient salts in exchange for products of photosynthesis. Such a symbiosis exists among others, the following types:

• Emperor Ling (Amanita Caesarea )
• Green amanita (Amanita phalloides )
• Panther mushroom ( Amanita pantherina )
• Amanita gilberti
• Mr. Mushroom (Boletus edulis)
• Russula rubra

Diseases and predators

Several butterfly species damage the cork oak, the most important is the gypsy moth ( Lymantria dispar ). The species lays its eggs in the bark of the branches and trunks, which hatch in the spring caterpillars spread in the crown and eat them bare. As a biological pesticide against the gypsy moth, the bacterium Bacillus thuringiensis is used. Another pest is the green oak ( Tortrix viridana ), whose caterpillars eat into flowers and young leaves and roll up with this web threads to typical coiling. Damage to the leaves also directed the Lackey Moth ( Malacosoma neustria ) at which attaches its eggs in multi-row rings on the bark of thin twigs, and also the gold After ( Euproctis chrysorrhoea ), whose caterpillars skeletonize the leaves and damage the tree continues after hibernation in spring. A special Korkschädling is the jewel beetle Coraebus undatus, which lays its eggs in the cork tissue. An equally harmful beetle is the great capricorn beetle ( Cerambyx cerdo ), whose larvae feed on long passages in the oak.

Unfavorable climatic conditions and fungi are responsible for the weakening of trees and crown damage. Such weakness fungal parasites are Diploida mutila, Hypoxylon mediterraneum, Endothiella gyrosa and representatives of the fungus genus Fusarium. Drought and infestation by parasites are also the cause of the weakness syndrome in parts of Spain and Portugal.

Systematics and etymology

Quercus suber is a type of Cerris section, which also includes the following types:

• Walloons oak ( Quercus macrolepis )
• Turkey oak (Quercus cerris )
• Quercus crenata
• Macedonian oak (Quercus trojana )

Characteristic of the section are the hairless pericarp and usually two years to mature the fruit. The cork oak in this case represents an exception because the fruit can mature both in the first and in the second year.

In the manner of Quercus suber two subspecies are distinguished:

• Quercus suber subsp. suber: nominate
• Quercus suber subsp. occidentalis (syn. Quercus occidentalis): It differs from the nominate form by the shape of the cupula - shed, the longer duration of development of the fruit and the semi-evergreen foliage. The range of the subspecies is the Portuguese Atlantic coast.

With the Turkey oak (Quercus cerris ) and the holm oak (Quercus ilex ) constitutes the cork oak species hybrids.

The scientific name Quercus suber is derived from the Latin word quercus, the Romans designated (Quercus robur ) with the common oak. The specific epithet is Latin suber cork oak and cork.

Use

The cork oak is grown for the production of cork in several Mediterranean countries. The centers of the cork are in southern Portugal and southern Spain, where low trees with large crowns and strong branches are grown on large areas, which provide the highest yield of cork. This largely extensively managed habitats are called dehesa in Spain and in Portugal montados. From the viewpoints of biodiversity and cultural heritage, they are considered highly valuable.

The cork consists of dead air-filled, thin-walled cells, and contains cellulose and suberin. Cork is heat and sound insulation, the suberin gives it water-repellent properties. The cork layer is simulated by korkproduzierenden cork cambium and therefore can be repeatedly harvested without damaging too much the tree. The first harvest takes place after about 12 to 15 years with a trunk diameter of 20-30 centimeters ( BHD). The first layer of cork is called " male cork ", is still very elastic and cracked and is only used for insulation blankets. Only the following Korkernten provide a higher-quality cork, the " female cork ", which can be commercially exploited in full. The best quality cork is obtained in the second, third and fourth harvest. Korkernten occur every nine to twelve years, if a layer thickness of from 2.7 to 4 cm is reached. Under favorable ( warm ) conditions, the harvest every eight years can be done in North Africa every seven years. Overall, a cork can be five to ten times harvested. In order to keep the violation of the trunk surface small, can alternatively also be harvested every three years, with only one-third of the usable surface is removed. An important maintenance operation is the pruning that begins with an age of about ten years and recorded a height to three meters. An oak delivers their lifetime about 100 to 200 kg cork, one hectare of about 200 to 500 kilograms per year.

The cork is mainly used in the manufacture of stoppers and cork, next to the thermal and acoustic insulation and for other technical applications (including composite materials, shoe soles, floor coverings ). The Flaschenkorkproduktion makes up about 70 % of the value of the Korkanbau. Since the natural corks are increasingly being replaced by plastic or metal closures, it could lead to a significant decline in cork oak stands in southwest Europe that threatens the biodiversity in these areas.

To use the cork

Is also used the bark, which contains about twelve percent extractable tannin. In addition, the acorns be used as feed in the extensive pig ( acorn ). A tree can supply 15 to 30 kilograms of acorns a year.

Cork oak as a symbol

• The cork oak is performed in Portugal of several cities in the city arms, so from the town of Reguengos de Monsaraz, showing a freshly harvested cork tree.

• In 2007, a 2- euro commemorative coin was issued with the motif of a cork tree to commemorate the Portuguese Presidency of the European Union in Portugal.

Portuguese commemorative coin 2007

Evidence