Teak tree
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Teak tree ( Tectona grandis ) |
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The teak tree ( Tectona grandis ) or teak [ tik ] is a plant from the family of Lamiaceae (Lamiaceae). It is native to the deciduous monsoon forests of South and Southeast Asia. The teak tree provides a very valuable wood and is one of the most important export woods in Asia. The German name teak is derived from English from the South Indian language Malayalam .
description
Appearance, root and bark
The teak tree is a tall, mostly deciduous to semi-evergreen tree that usually reaches heights of 25 to 35 meters, rarely more than 40 meters. The trunks are usually cylindrical, but they can also have an irregular cross-section and develop narrower buttress roots , corrugations or roots with age . Straight trees are found in Thailand and Myanmar . The crown is usually very high, branch-free usable trunk lengths of 20 to 25 meters can be achieved with a chest height diameter of 100-200 centimeters. The crown is very shady. The root system is a superficial, horizontally spreading heart root system . The gray to gray-brown and usually one to 1.5 centimeters thick bark is longitudinally fissured, quite soft and flakes off. The branches are square.
Foliage leaf
The large and soft, simple leaves , arranged opposite or in threes in whorls on the branches, are sitting or have a petiole up to 5 centimeters long. The simple, entire and sometimes dentate leaf blade is 30 to over 60 centimeters long and 20 to over 35 centimeters wide - elliptical to lanceolate or ovate and more or less pointed to rounded. The upper side of the leaf is dark green and bare, the underside light green to yellowish green and densely hairy. The veins are pinnate and raised on the underside.
Inflorescence and flower
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Many flowers are in up to 45 by 40 centimeters, terminal or axillary and paniculate , fine-haired and richly branched inflorescences at the branch ends. Are attached to the lateral axes and the other branches, as well as the individual flower supporting sheets formed.
The hermaphrodite, fragrant and small, short-stalked flowers are about 7 to 8 millimeters in size with a double flower envelope . The multi-lobed calyx is hairy white-gray and bell-shaped. The bald crown is white to cream-colored and funnel-shaped with 5–7 spreading lobes. The 5–7 stamens sit in the throat. The above constant, hairy ovary is vierkammerig, ovate to conical and has a lobed scar , the scar cloth do not always open.
The flowering time is in the rainy season , between June and September. The Blühreife occurs, depending on the environmental conditions at the age of five to 20 years. The pollination is effected by insects ( Entomophilie ).
Fruit and seeds
The fruit ripens 2.5 to 3 months after flowering. The fruits are spherical drupes of about 1.2–2 centimeters in diameter, which are hidden in an inflated and balloon-like shell that is made from the sepals and is brown and papery when ripe. The light brown stone core is fourfold, but mostly only one to three seeds are formed. The exocarp is densely whitish and furry, the mesocarp is porous, corky and the ribbed-furrowed endocarp is hard, bony. The flattened and egg-shaped, whitish, smooth seeds have a thousand-grain mass of about 430 to 900 grams. The teak tree produces abundant seeds every year.
The germination is slow and irregular.
Wood
The wood has a light-colored sapwood two to three centimeters thick. The heartwood is yellow to dark brown in color. The wood is streaked by dark olive-brown to black stripes (black stripe teak). This color comes from different concentrations of phytochemicals, including dehydrotectol and tectoquinone. These stripes appear particularly on teak of Burmese origin. The silicon content of the wood also depends on the area of origin.
| Technical wood data | |
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| Bulk density (r 10–15 ) | 0.55-0.75 g / cm³ |
| Compressive strength | 52-60 N / mm² |
| tensile strenght | 120 N / mm² |
| Flexural strength | 85-110 N / mm² |
The trunk cross-section shows clear growth zones, which are caused by the seasonal tropical climate . Several growth spurts can occur within a year.
The wood is usually straight grain. Interlocked growth rarely occurs.
The cellulose content is about 43%, of the lignin proportion of 30 to 39%. In the parenchyma of the outer heartwood, teak stores rubber , up to 5 percent by weight. This exceptionally high rubber content causes the sticky, oily texture and the dull surface of the wood, as well as high abrasion resistance , acid resistance and the wood's strong water repellency.
The heartwood is very durable. The causes are the secondary plant substances Tectol , which has a fungicidal effect, and Tectoquinone , which causes resistance to insects. The high silicon content also contributes to the resistance to insects (especially termites ) and bivalve molluscs . Because of these resistance properties, teak is also well suited for wooden shipbuilding .
distribution
The teak tree is native to South and Southeast Asia. The natural area is divided into two parts, which are separated by the plains of the Ganges - Brahmaputra delta: India on the one hand, Myanmar , Northern Thailand and part of Laos on the other. In the east, the Mekong is the natural limit of distribution.
In India, teak grows on around eight million hectares, half of it in the state of Madhya Pradesh . No figures are known from Myanmar. In Thailand, the natural area covers around three million hectares, while in Laos it is only around 70,000 hectares.
Outside of this natural area, the teak tree is planted all over South Asia and in the entire tropical region: In Indonesia it was introduced to Java between the 14th and 16th centuries . Today teak covers around 800,000 hectares on Java, Kangean and Muna . It was also introduced in Africa ( Ivory Coast , Cameroon , Nigeria , Tanzania , Togo , Zimbabwe ) and Latin America ( Argentina , Ecuador , Honduras , Trinidad ) at the beginning of the 20th century . The teak reforestation areas total around 1.1 million hectares.
ecology
Since the distribution area is very large and geographically very heterogeneous, there are numerous breeds of teak trees. These differ in their habitus and in the demands on climate and soil.
The teak tree is a type of light tree . It needs full skylights in all stages of life, but especially as a young plant. The teak tree is bound to a balanced temperature profile and has a high need for warmth. The annual mean temperature in the natural range is 21 to 26 ° C, the physiological optimum is 24 to 25 ° C. The absolute minimum temperatures are 2 ° C, the teak tree does not tolerate frost.
The annual precipitation shows great differences across the distribution area. In India, the teak tree grows with around 780 mm of rainfall and five to seven months of dryness. In Myanmar it grows with 1500 to 2500 mm of precipitation in the semi-evergreen wet forest.
Natural teak forests grow on limestone and clay soils , also on laterite , especially in the hilly and lower mountain regions. Depending on the area, the teak tree usually occurs at altitudes between 400 and 900 meters. The tree produces the best growth performance on well-watered, deep and well-aerated soils with a neutral to slightly acidic pH value . It finds these conditions especially on sandy loams and alluvial clay soils. The teak tree is very sensitive to waterlogging and a lack of oxygen in the soil.
The teak tree is deciduous. He is bald for three to five months. The leaves are shed in the dry season (December to March), the new leaves appear shortly before the start of the rainy season. In the ever-humid climate of West Java, however, the teak tree is evergreen.
Pests
The teak tree is considered to be relatively stable against biotic and abiotic damaging factors.
The caterpillars of various butterfly species can cause certain damage by eating their leaves, and various semi-parasitic species of the genus Loranthus can also attack the tree.
The heartwood is rarely attacked, e.g. B. wood-boring insects ( Xyleutes ceramicus ) and fungal core rot pathogens .
Phytopathogenic viruses and bacteria are very rare. Important fungal pathogens are the following: Armillaria mellea , Fomes lignosus , Fomes noxius , Heterobasidium compactum , Irpex flavus , Nectria species, Olivea tectonae ("teak leaf rust"), Peniophora rhizomorpha ("yellow laminated rot"), and Polyporus zonalis ( "White pocket red").
Elephants can cause kicking and peeling damage in plantations . Against fire of the teak tree is relatively resistant.
Systematics
The genus Tectona has been part of the Lamiaceae family for a few years , but many books still mention the older affiliation to the Verbenaceae family .
The name Tectona is derived from the Portuguese teca = teak from Malayalam tekka = teak. At the same time, the name is based on the Greek τέκτων tékton = carpenter. The specific epithet grandis is the Latin word for big.
Related species
In addition to Tectona grandis , the genus Tectona also includes the following species:
- Tectona hamiltoniana Wall. : It occurs from Myanmar to the Malay Peninsula.
- Tectona philippinensis Benth. & Hook.f. ex Merr. : It occurs in the Philippines.
use
The main use of the teak tree concerns its wood . In addition to the tall, knot-free trunks, its special properties make the wood valuable. It is easy to work with and dries without tearing or throwing . Thanks to its natural oils, the surface remains attractive and weatherproof even without subsequent treatment. However, the rubber content makes glueing more difficult, and other ingredients make painting and artificial coloring more difficult , so that special glues and varnishes have to be used for these purposes . Instead of painting teak furniture, it is often treated with teak oil .
The wood is very durable, which is due to the ingredients listed above. The heartwood in particular is very resistant to fungi and insects (termites). In addition, the wood is flame retardant.
Due to its color, teak is used as a sliced veneer or solid wood for furniture, paneling and as parquet . Above all, its use in boat and shipbuilding is important . A teak ship deck does not become slippery when wet. It is also used for water and harbor structures because of its durability. It is also used for turning and carving as well as for model making because of its easy workability. However, the tools quickly become blunt, which is why the use of hard metal is advisable.
In the natural range, the wood is also used as firewood, for the production of charcoal and for household appliances. The leaves are used to dye fabrics red. Flowers , leaves, bark and wood are used in folk medicine against enteritis and against fever.
The natural teak stocks are particularly endangered by shifting cultivation and illegal logging .
The main export countries are Indonesia and Myanmar .
Cultivation
Along with mahogany, teak is one of the few tropical timber that can be grown in plantations . As a light tree species, Tectona grandis is very well suited for open space afforestation.
The teak tree reproduces generatively , i.e. via seeds . The afforestation of areas is done either by direct sowing or by means of stump planting . Here, seedlings are grown in tree nurseries . At eight to ten months, when the root neck diameter is 1 to 2.5 centimeters, the young plants are shortened to a root length of 10 to 25 centimeters and a shoot length of two to five centimeters. These stumps are then exposed on the surfaces. The distances between the trees are between 1.8 × 1.8 and 2 × 2.5 meters. Mostly pure stands are planted, more rarely mixed stands such as the white mulberry . Soil-strengthening secondary tree species are planted more often ( Leucaena leucocephala , acacias ) to reduce soil erosion . Maintenance measures such as free cutting are only necessary in the first year, as the plants reach a height of three meters in the second year.
In Java in particular, teak has also been grown in the Taungya system , a variant of agroforestry, since the 19th century . After deforestation of the forest authorities Vorbestandes the land over to the farmers here. These clear the areas of residual forest and sow agricultural crops, especially dry rice and maize . At the same time, teak is sown. Later, the shrubby is legume Leucaena leucocephala sown whose twigs u. a. is used for mulching . After mostly two maize and one rice harvests, the forest authorities take over the land again.
In addition, teak is also grown in conventional plantations and in irrigated plantations.
The rotation times in (fast-growing) plantations are around 18 to 25 years, in natural stands at 60 to over 100 years.
literature
- The CABI Encyclopedia of Forest Trees. CABI, 2013, ISBN 978-1-78064-236-9 , p. 460 ff.
- M. Schorcht: Tectona grandis. In: Peter Schütt et al .: Trees of the Tropics. Nikol, Hamburg 2006, ISBN 978-3-933203-79-3 , pp. 635-644.
- W. Nutsch et al .: Wood technology. Expertise for carpenters. EUROPA Lehrmittel, Nourney, Vollmer, 1987, ISBN 3-8085-4013-3 , p. 68.
Web links
- Special edition of Unasylva magazine on teak
- Diego Perez: Stand growth scenarios for Tectona grandis plantations in Costa Rica . (Dissertation)
- Tectona grandis . In: U. Brunken, M. Schmidt, S. Dressler, T. Janssen, A. Thiombiano, G. Zizka: West African plants - A Photo Guide. Senckenberg Research Institute, Frankfurt am Main 2008.
- Tectona grandis at Useful Tropical Plants.
Individual evidence
- ↑ a b Helmut Genaust: Etymological dictionary of botanical plant names. 3rd, completely revised and expanded edition, Nikol, Hamburg 2005, ISBN 3-937872-16-7 , pp. 632, 273 (reprint from 1996).
- ↑ According to schreiner-seiten.de
- ↑ H. Walter, S.-W. Breckle: Ecology of the Earth. Volume 2: Special Ecology of Tropical and Subtropical Zones , 3rd edition, Elsevier, Munich 2004, ISBN 3-8274-0789-3 , p. 204.
- ↑ See APG mobot.org .
- ↑ a b Rafaël Govaerts (Ed.): Tectona. In: World Checklist of Selected Plant Families (WCSP) - The Board of Trustees of the Royal Botanic Gardens, Kew . Retrieved January 6, 2019.
- ↑ Turismo de Timor-Leste: Tais: The Textiles of Timor-Leste ( Memento from January 27, 2007 in the Internet Archive )
- ↑ M. Schorcht: Tectona grandis , 2006, p. 643