Black mangrove
| Black mangrove | ||||||||||||
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Single black mangrove in Everglades National Park |
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| Scientific name | ||||||||||||
| Avicennia germinans | ||||||||||||
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The Black Mangrove ( Avicennia germinans ) is occurring in the tropics and subtropics of America and West Africa Mangrove . There she dominates together with the Red Mangrove ( Rhizophora mangle ) and white mangrove ( Laguncularia racemosa ), the mangrove forests . Like all mangroves of the genus Avicennia, it has pencil- sized breathing roots that protrude from the ground at regular intervals and serve to supply the root system with oxygen. Stilt roots as in other mangrove genera are not formed. Some of the salt absorbed from the sea water is excreted as a salty liquid through glands on the leaves and in this way the salt concentration in the tissue is regulated. Of all Avicennia species, the black mangrove has the largest flowers.
description
Manifestation
The black mangrove is an evergreen tree that reaches heights of growth of 25 meters and a trunk diameter ( BHD ) of 40 centimeters. Its dimensions are often smaller, so in Puerto Rico it reaches heights of growth of 3 to 13 meters and a trunk diameter of 30 centimeters. The species grows shrub-like near the northern area boundary in Florida . The trunk is usually crooked and short, the crown wide.
Bark and wood
The bark can be black, dark brown to reddish brown or gray and shows isolated cork pores ( lenticels ). It is somewhat longitudinally fissured and comes off in thin scales. The yellow to orange inner bark is characteristic of the species .
The wood is very hard and a little oily. It has a light, fairly wide sapwood , the heartwood is dark brown. Like the other species of the genus Avicennia , the black mangrove has an abnormal secondary growth in thickness : the wood shows regular growth zones that are not annual rings . Each ring consists of xylem , phloem and a transitional tissue that stands out as a white stripe. The width of the growth rings is not influenced by the climate or other environmental factors; the number of rings newly formed per year varies.
Root system
In the usually soft substrates, roots that run flat and extend far beyond the crown diameter are formed. What is striking are the respiratory roots (pneumatophores) typical of Avicennia species , which are formed as upright (i.e. negatively geotropic, growing against gravity) side roots in large numbers and at regular intervals of 15 to 30 centimeters on the long main roots. They protrude up to 30 centimeters from the ground, are about the thickness of a pencil, and supply the root system with oxygen from the atmosphere . Around 10,000 pneumatophores are formed from a tree two to three meters high. In addition to the horizontal main roots and the pneumatophores, the root system also consists of the positively geotropic growing side roots, which serve to absorb nutrients and anchor. Stilt roots like those of the red mangrove ( Rhizophora mangle ) are not formed.
Branches and leaves
The branches are divided into 1 to 9 centimeters long internodes with an approximately square cross-section, which are separated by clearly thickened nodes . Numerous aerial roots are formed from the higher branches of strong trees .
The cross-opposite leaves on the branches are leathery, narrow, elliptical and have entire margins. They are 4.5 to 15 inches long and 1.8 to 4.5 inches wide. The short petioles are 2 to 27 millimeters long and stiffened on the upper side in a groove, the underside is convex . The upper side of the leaf is rich green to yellow-green and shiny, the underside is silvery gray-green and densely covered with fine hairs. The apex can be both pointed and blunt, the base of the blade is tapered in a wedge shape. The salt crystals , which are often visible on the leaf blades, are characteristic. The excess salt is released through microscopic salt glands in the leaves.
blossoms
The black mangrove forms the largest flowers of the genus Avicennia . It blooms in loose, less often dense, terminal or axillary, spiked , 1.5 to 6.6 centimeters long and 1 to 1.5 centimeters wide inflorescences with one to 15 flowers each. The small, hermaphrodite, zygomorphic , sweet-smelling flowers are 1 to 2 centimeters long. The five light green, 3 to 5 millimeter long sepals are fused together like a jug. The four white, cream-colored or yellowish petals are fused together like a bell, with the corolla having a length of 12 to 20 millimeters. Four stamens attached to the base of the petals are formed. The stamp has a double-lobed scar . The black mangrove provides plenty of nectar and thus attracts a large number of insects . The main flowering season in the Caribbean and Florida is from May to July.
fruit
Round to elliptical, thin-walled, light green, 2.5 to 3.8 centimeters long and 7 to 13 millimeters wide capsule fruits are formed. They contain a single seed with no seed coat and no endosperm . It consists only of the embryo with two large, greenish, folded cotyledons , a thick radicle and a bud (plumula) that cannot be seen with the naked eye . The seed ripening falls mainly in the months of September and October.
Distribution and location requirements
The black mangrove is found in America and West Africa. Their distribution area in America includes the West Indies including the Bahamas without Dominica , both coasts of Central America, the Pacific coast of South America to Ecuador and offshore archipelagos with the Galápagos Islands , and the South American Atlantic coast to Brazil . In the United States , their natural occurrence extends to southern Florida, the Mississippi Delta, and Texas . In West Africa, the species is found on the Atlantic coast from Mauritania to the Democratic Republic of the Congo .
The natural occurrence is limited to the sea coast. Locations at altitudes over 15 meters such as on the coast of El Salvador are an exception. The species grows in the brackish water area of protected, muddy coasts, especially in the estuary of rivers. It tolerates high salt concentrations, but also grows in fresh water and does not require any salt. It prefers soils with pH values between 5.3 and 7.8. Like other mangroves, the black mangrove is a species of the tropics . Occurrences in the subtropics are exceptional. These are found in warm ocean currents that emanate from densely populated tropical areas and run along chains of islands, thus promoting the spread. These conditions exist in the subtropical part of Florida.
The black mangrove is listed on the IUCN Red List as Least Concern.
ecology
Mangrove forests occur on tropical and subtropical ocean coasts. Their environment is characterized by the salt water, the tides , the underground consisting of low-oxygen silt and high temperatures and high humidity.
Salt balance
Mangroves are rooted in salty soil, so they are salty plants . Since a high salt content damages the plant, the accumulation in the tissue is prevented. Even when the water is absorbed by the roots, only a small part of the salt is absorbed, although members of the Avicennia genus absorb a lot by comparison (compared e.g. with Rhizophora mangle ). The salt content in the xylem reaches values of around 10% of the salt content of seawater. To avoid too high a salt concentration, excess salt is excreted through the salt glands on the upper and lower sides of the leaves. During the rainy season, the salinity of the excreted liquid can reach half the salinity of seawater; during the dry season, the salinity can be the same as that of seawater. About 0.2 to 1.2 grams of salt are released per square meter of leaf area and day. It is washed off by rain or, if the water from the excreted liquid evaporates, it can crystallize on the leaves.
Respiratory roots
The soil of the mangrove forests mostly consists of low-oxygen silt. To ensure the oxygen supply to the root system, representatives of the genus Avicennia form respiratory roots, so-called pneumatophores . These protrude from the water at least at low tide and are in contact with the atmosphere. The gas exchange takes place through cork pores in the roots of the breath, the further transport through cavities, which can make up 40% of the total volume of the root system.
Pollination and Spread
The main flowering period in Florida and the Caribbean is from May to July. Pollination is carried out by insects, mostly bees. As is common in the Avicennia genus, germination begins in the fruit on the tree without the seedling leaving the fruit ( cryptoviviparia ). The seeds ripen from September to October, and fruits can be transported far by the current. Seedlings can survive for a very long time when drifting.
Community
Mangrove forests are usually divided into zones, which are characterized by different species depending on their proximity to the sea. After the red mangrove, the black mangrove and the white mangrove ( Laguncularia racemosa ) populate the next inland zone, which can only be reached by high tides. On the South American east coast the distribution area overlaps with the species Avicennia schaueriana , on the Pacific coast of Central America with Avicennia bicolor and Avicennia tonduzii .
The mangrove forests serve as a breeding ground for many fish and crustaceans , with the root system providing protection and the foliage providing food, such as the square crab Goniopsis cruentata or the mangrove crabs Ucides cordatus and Aratus pisonii . Ibises , pelicans and various species of herons have their nesting sites in the mangrove forest.
In western Africa, mangrove forests are an important wintering habitat for Palearctic songbirds. In the area between 12 and 16 ° N, five to six million reed warblers winter there , but also other species such as the white-bearded warbler . In Avicennia in particular, high densities of up to 21 overwinterers per hectare were found there.
Systematics
Genetic studies show a closer relationship between specimens on the east coast of America and the west coast of Africa than between the two opposite coasts of America. This indicates the maintenance of gene exchange across the Atlantic. However, the differences to the specimens on the west coast of America are not so great that a division into subspecies would be justified. The form Avicennia germinans var. Guayaciliensis can be distinguished from the species itself . It occurs on both the west and east coasts of America, which speaks in favor of the separation even before the land bridge between North and South America was built .
The genus Avicennia used to be part of the verbena family (Verbenaceae). Today it is regarded as a separate family Avicenniaceae or as a subfamily Avicennioideae in the family of the acanthus plants (Acanthaceae).
Botanical history
The black mangrove became famous in Europe for parts of plants that were collected in Jamaica by the Irish medic and botanist Patrick Browne . Parts of it with others from Venezuela were used by Carl von Linné in 1759 to describe the species as Bontia germinans in the tenth edition of his work Systema Naturae ( Basionym ). In the second edition of his Species Plantarum published in 1763, he also used the name for parts of plants from India, which he had described in the first edition as Avicennia officinalis . Since it soon became apparent that there were two species, the name Avicennia nitida by Nikolaus Joseph von Jacquin was established for the American species . In West Africa the species of Palisot de Beauvois was described as a separate species Avicennia africana . As late as 1960, differences between the African and American representatives in the color and shape of dried leaves from specimens were cited. Today the West African representatives are also assigned to the species Avicennia germinans , which is confirmed by molecular studies. The names Avicennia africana and Avicennia nitida are synonyms .
The generic name Avicennia is reminiscent of the Persian doctor and philosopher Avicenna , the epithet germinans means "germinating" and indicates that the seed is still germinating on the tree.
use
Due to its hardness, the wood is difficult to work with and the wood dust causes skin infections. Therefore it is rarely used, as it used to be for making furniture. Today it is rarely used as lumber, as telegraph poles, or for footbridges, piers, and railroad ties. It is used as firewood and can be processed into charcoal. The wood has a high density of around 950 kg / m³, it is durable, but not resistant to termites .
The black mangrove is a productive pasture for bees, resulting in a pure, white honey that is known in Florida under the name "Mangrove Honey". The salt crystals secreted by the leaves can be used to season dishes. Two leaves are enough for a bowl of soup. The seeds are poisonous raw, but can be eaten cooked, but this only happened in times of starvation.
proof
literature
- P. B. Tomlinson: The Botany of Mangroves . Cambridge University Press, Cambridge 1986, ISBN 0-521-46675-X .
- Schütt, Weisgerber, Schuck, Lang, Stimm, Roloff: Trees of the tropics . Nikol, Hamburg 2006, ISBN 3-933203-79-1 , p. 87-93 .
- R. S. Dodd, Z. Afzal-Rafii, N. Kashani, J. Budrick: Land barriers and open oceans: effects on gene diversity and population structure in Avicennia germinans L. (Avicenniaceae) . In: Molecular Ecology . tape 11 , no. 8 , 2002, p. 1327-1338 , doi : 10.1046 / j.1365-294X.2002.01525.x (English).
Individual evidence
- ↑ a b c d Schütt et al .: Trees of the Tropics , p. 89
- ↑ a b c d e Schütt et al .: Trees of the Tropics , p. 90
- ^ Tomlinson: The Botany of Mangroves , p. 109
- ↑ a b c Tomlinson: The Botany of Mangroves , p. 205
- ↑ a b c d e f Dodd et al .: Land barriers and open oceans: effects on gene diversity and population structure in Avicennia germinans L. (Avicenniaceae)
- ↑ a b Schütt et al .: Trees of the Tropics , p. 88
- ↑ a b c Avicennia germinans (L.) L. In: Germplasm Resources Information Network. National Germplasm Resources Laboratory, accessed April 19, 2009 .
- ↑ a b Cristina Garibaldi (Department of Botany, University of Panamá): Avicennia germinans (L.) L. (PDF) In: Tropical Tree Seed Manual, Species Descriptions. Reforestation, Nurseries, & Genetic Resources, 2003, pp. 315-317 , accessed March 19, 2008 .
- ↑ a b K. Hill: Avicennia germinans. Smithsonian Marine Station at Fort Pierce, July 25, 2001, accessed March 18, 2008 .
- ^ Tomlinson: The Botany of Mangroves , p. 57
- ↑ Avicennia germinans in the endangered Red List species the IUCN 2010. Posted by: Ellison, A. Farnsworth, E., Moore, G., 2007. Retrieved on January 2 2011th
- ↑ Tomlinson: The Botany of Mangroves , pp. 121-123
- ^ Tomlinson: The Botany of Mangroves , p. 96
- ^ Tomlinson: The Botany of Mangroves , p. 108
- ^ Tomlinson: The Botany of Mangroves , p. 135
- ^ Tomlinson: The Botany of Mangroves , p. 151
- ^ Tomlinson: The Botany of Mangroves , p. 159
- ↑ a b Schütt et al .: Trees of the Tropics , p. 91
- ↑ Schütt et al .: Trees of the Tropics , p. 92
- ↑ Leo Zwarts, Jan van der Kamp, Erik Klop, Marten Sikkema, Eddy Wymenga: West African Mangroves Harbor Millions of Wintering European Warblers , Ardea 102/2, pp. 121–130, 2014, doi: 10.5253 / arde.v102i2.a2
- ↑ HN Moldenke: Materials towards a monograph of the genus Avicennia L. In: Phytologia . No. 7 , 1960 (quoted from Dodd et al .: Land barriers and open oceans: effects on gene diversity and population structure in Avicennia germinans L. , pp. 1335-1336).
- ^ Avicennia. In: Flora of China Vol. 17. www.eFloras.org, p. 49 , accessed on April 23, 2009 (English).
- ↑ HN Moldenke: Materials towards a monograph of the genus Avicennia L. In: Phytologia . No. 7 , 1960 (Quoted from Tomlinson: The Botany of Mangroves , p. 205 and Dodd et al .: Land barriers and open oceans: effects on gene diversity and population structure in Avicennia germinans L. , p. 1328).
- ↑ Lotte Burkhardt: Directory of eponymous plant names . Extended Edition. Botanic Garden and Botanical Museum Berlin, Free University Berlin Berlin 2018. [1]
- ↑ a b c Schütt et al .: Trees of the Tropics , p. 93
- ^ Tomlinson: The Botany of Mangroves , p. 167
Web links
- Avicennia germinans . 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.
