Bruguiera gymnorhiza

Family

Rhizophoraceae

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Chromosome number

2n = 36

Synonyms

Vernacular names

Black mangrove, Burma mangrove (En). Palétuvier noir, manglier noir (Fr). Mangue encarnado, pau salgado macho (Po). Mshinzi, muia, mkoko wimbi (Sw).

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Origin and geographic distribution

Bruguiera gymnorhiza occurs along the coasts of tropical eastern and southern Africa, Madagascar and other Indian Ocean islands, through tropical Asia to north-eastern Australia, Micronesia and Polynesia. The tropical Asian area probably represents the centre of origin.

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Uses

The bark of Bruguiera gymnorhiza is rich in tannin and suitable for tanning leather and for treating sails and fishing nets for longer preservation. The bark provides orange to reddish brown dyes without mordanting, and purplish brown, grey and black colours if the fibres or textiles are treated with iron-rich mud or iron salts.
Planks up to 7 m long can be obtained from the bole, and these are used for piles, house posts, rafters, fishing stakes, and electricity or telephone poles. The wood is more commonly used for firewood and charcoal. It can also be used for the paper industry, but the paper is of poor quality. The bark is used as a condiment (e.g. with fish), adhesive and as an astringent medicine against diarrhoea and sometimes malaria. The fruits are sometimes used as an eye medicine. In Mauritius a decoction of the root, mixed with leaves of Piper pyrifolium Vahl, is drunk against bleeding, diabetes and hypertension. The leaves and peeled hypocotyls, soaked in water and boiled, can be eaten as a vegetable in times of scarcity. Occasionally Bruguiera gymnorhiza is planted to prevent or combat erosion along coasts.

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Production and international trade

The main countries producing tannin from Bruguiera gymnorhiza are East African countries, Indonesia (Kalimantan), Papua New Guinea and the Philippines. At present Borneo accounts for an important proportion of world supplies. However, no figures are available because bark and tannin from Bruguiera gymnorhiza are sold together with bark and tannin from other mangrove trees such as Rhizophora and Ceriops species, collectively called ‘mangrove cutch’. In many countries the production of tan bark is only of secondary importance behind the exploitation for charcoal, fuel and timber. Bakau is an international trade name for the timber of Bruguiera, Ceriops and Rhizophora. In eastern Africa, the largest mangrove timber poles usually originate from Bruguiera gymnorhiza and are called ‘nguso’ or ‘vigingi’ in Swahili.

Properties

The percentage of tannin in the bark can vary from 20–43% on dry weight basis, depending on age, season and habitat. The bark of the trunk of large, aged trees is richest in tannin. The tannins belong to the group of condensed tannins of the proanthocyanidin type, which can rearrange in mild alkaline conditions to produce reddish dyes, the phlobatannins. Ellagic acid and di- and tri-O-methylellagic acid have also been identified in the bark. The tanning stuff imparts a reddish colour to leather, and is often mixed with other less colouring tannins in the tanning industry. It is suitable for tanning heavy hides into sole leather. Other parts of the tree also contain tannins (e.g. about 13% in the leaves). The bark contains about 11% mucilaginous sap, which is mainly composed of arabinose, rhamnose and galactose, and also 0.05% of a mixture of bruguierol and isobruguierol (ratio of 5 : 1).
The heartwood is red brown and distinctly demarcated from the pale brown sapwood. The grain is usually interlocked, texture fine and even. The wood is heavy with a density of about 975 kg/ m³ at 15% moisture content. At 15% moisture content the modulus of rupture is 123.5 N/mm², compression parallel to grain 68 N/mm², shear 13.5–16 N/mm², cleavage 45 N/mm radial and 63.5 N/mm tangential, Janka side hardness 10,300 N and Janka end hardness 7960 N. The rates of shrinkage are moderate, from green to 12% moisture content 2.5% radial and 5.5% tangential. Logs shrink and check excessively during seasoning. The wood is strong and hard. It works and finishes well. It is moderately durable when exposed to the weather or in contact with the ground; poles may have a service life of 10 years. The wood is easy to treat with preservatives and absorbs 200 kg/m³. The energy value of the wood is 18,950–20,200 kJ/kg.

Description

Medium-sized, evergreen tree up to 36 m tall; bole up to 65 cm in diameter, buttressed; bark grey to almost black, roughly fissured, usually with large corky lenticels on buttresses and base of stem; knee roots or pneumatophores present. Leaves decussately opposite, simple, and entire; stipules c. 4 cm long, often reddish; petiole 2–4.5 cm long, often reddish; blade elliptical to oblong, 8–22 cm × 5–9 cm, base cuneate, apex acute, leathery, glabrous, pinnately veined. Flowers solitary, 3–3.5 cm long, generally nodding; pedicel 1–2.5 cm long, bright red on the outside curve; calyx tubular for 1–2 cm, 10–16-lobed with lobes narrowly long-triangular and up to 2 cm long, red to pink-red, tube usually ribbed at the upper part; petals as many as calyx lobes, white or cream, 13–15 mm long, 2-lobed, each lobe with 3–4 long bristles, outer margins fringed with white silky hairs especially at the base; stamens in pairs embraced by the petals up to 11 mm long, with linear anthers; ovary inferior, usually 3-celled, style about 15 mm long with filiform stigma. Fruit a campanulate berry enclosed by the calyx tube, 2–2.5 cm long, 1-celled and 1(–2)-seeded, viviparous. Seedling with cigar-shaped hypocotyl, slightly angular, 15–25 cm × 1.5–2 cm, with a blunt narrowed apex, perforating the apex of the fruit and falling with it.

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Other botanical information

Bruguiera comprises 6 species, which are all used outside Africa in the same way as Bruguiera gymnorhiza. The other species are widespread from tropical Asia to Australia and Polynesia in mangrove vegetations, and their barks usually contain less tannin.

Anatomy

Wood-anatomical description (IAWA hardwood codes):
Growth rings: 2: growth ring boundaries indistinct or absent. Vessels: 5: wood diffuse-porous; (10: vessels in radial multiples of 4 or more common); 14: scalariform perforation plates; 15: scalariform perforation plates with ≤ 10 bars; (16: scalariform perforation plates with 10–20 bars); 20: intervessel pits scalariform; 31: vessel-ray pits with much reduced borders to apparently simple: pits rounded or angular; 32: vessel-ray pits with much reduced borders to apparently simple: pits horizontal (scalariform, gash-like) to vertical (palisade); 34: vessel-ray pits unilaterally compound and coarse (over 10 μm); 41: mean tangential diameter of vessel lumina 50–100 μm; 47: 5–20 vessels per square millimetre; 48: 20–40 vessels per square millimetre; 56: tyloses common; 58: gums and other deposits in heartwood vessels. Tracheids and fibres: 61: fibres with simple to minutely bordered pits; (65: septate fibres present); 66: non-septate fibres present; 69: fibres thin- to thick-walled; 70: fibres very thick-walled. Axial parenchyma: 78: axial parenchyma scanty paratracheal; 93: eight (5–8) cells per parenchyma strand; 94: over eight cells per parenchyma strand. Rays: 98: larger rays commonly 4- to 10-seriate; 102: ray height > 1 mm; 105: all ray cells upright and/or square; 108: body ray cells procumbent with over 4 rows of upright and/or square marginal cells; 109: rays with procumbent, square and upright cells mixed throughout the ray; (110: sheath cells present); 115: 4–12 rays per mm. Mineral inclusions: 136: prismatic crystals present; 137: prismatic crystals in upright and/or square ray cells; 138: prismatic crystals in procumbent ray cells.
(L.N. Banak, H. Beeckman, P.E. Gasson & P. Détienne)

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Growth and development

Bruguiera gymnorhiza is viviparous, i.e. the seeds germinate while still attached to the tree. After the seedlings are released they fall vertically into the mud and become established rapidly. The tree develops according to Aubréville’s model of architecture characterized by a monopodial trunk having rhythmic growth and plagiotropic branches. It takes 40 years to attain 16 cm in bole diameter. Bruguiera gymnorhiza is one of the largest trees of the mangrove and probably the one living longest. Growth decreases with decreasing salinity, which happens in the process of sedimentation in mangrove forest. In eastern Africa Bruguiera gymnorhiza usually does not grow over 25 m, but on Chale Island (southern Kenya) specimens reach a height of over 30 m. Flowering is mainly from January to March and fruiting from April to July. The flowers are visited by birds such as honey eaters and by insects. The pouched petals ‘explode’ when triggered, scattering pollen on the visitor. The fruits (seedlings) are dispersed by water. They can remain alive, floating in the water, for 5–6 months, which may explain the large area of distribution.

Ecology

In eastern Africa, Bruguiera gymnorhiza is a component of mangrove vegetation consisting of 8–9 species. It is characteristic of the landward side of mangroves and can grow along the river beds upward as far as the tidal range, but it also is a common element of mangrove assemblages in the mid-intertidal zone inundated by normal high tides (or in some cases by spring tides only), where it is often mixed with Rhizophora mucronata Poir. and Ceriops tagal (Poir.) C.B.Rob. Although Bruguiera gymnorhiza is not recognized as a pioneering mangrove species, propagules from the tree are often found on exposed beaches where the mangrove belt is thin or depauperate. It usually grows on somewhat dry, well-aerated soil but also on mud, sand and occasionally black, peaty soils. It tolerates a pH of 6–8.5. Bruguiera gymnorhiza marks the climax vegetation of littoral mangrove forests, before the transition to land forest. It is shade tolerant and able to establish itself even in pure stands of Rhizophora. The regeneration after felling is usually scant or even absent. The temperature range for growth is 15–30°C with the optimum between 20–26°C. The annual rainfall range for growth is 1000–8000 mm with the optimum between 1500–2500 mm. Bruguiera gymnorhiza withstands flooding with fresh as well as salt water (maximum up to 3% NaCl), but is usually absent from the area nearest to the seaward edge.

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Propagation and planting

Natural regeneration of Bruguiera gymnorhiza is usually very common. Propagation by cuttings is very difficult and trees suffer when branches are taken off. Seedlings can be collected either from the trees or from the ground and they are equally viable. They can be planted in a nursery and transferred to the field 3–4 months later, at a space of 3 m × 1 m. Nurseries outside the mangrove forest should be made by planting fruits in polythene bags filled with brackish clay continuously soaked with seawater or a solution of approximately 30 g NaCl per l water. Seedlings develop best where the tidal range is only about 35 cm and the salinity 1–2.5%.

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Management

Little is still known about the silvicultural management of mangrove forests and little experimental work has been done on natural and artificial regeneration. In general, clear felling with natural regeneration can be carried out in strips perpendicular to the coast, leaving several mother trees. For Bruguiera gymnorhiza cutting cycles of 10–20 years have been suggested, but a rotation of 30 years is applied in mangrove forests in Thailand. Bruguiera gymnorhiza does not coppice. In mangrove forest the fern Acrostichum aureum L. becomes a weed and has to be controlled after the forest has been logged. Once seedlings have established themselves, the fern acts rather as a nurse, forcing the seedling up. Cutting Bruguiera gymnorhiza to extract tannin and produce charcoal leads to a gradual transformation into a Rhizophora-dominated vegetation. The slow growth of Bruguiera makes it more suitable for planting for charcoal or chipwood than for sawn timber. Experiments in Indonesia have shown that Bruguiera gymnorhiza can easily be planted and grown. It might be successfully used for reafforestation in areas where mangroves have been destroyed.

Diseases and pests

No serious diseases or pests are known for Bruguiera gymnorhiza. Seedlings may be attacked by mangrove crabs like Scylla serrata, Sesarma meinerti and Sesarma smithii. Sometimes plantations may suffer from caterpillars.

Harvesting

Bruguiera gymnorhiza is mostly harvested from natural stands. There is no particular season for bark harvesting. After the trees have been felled, the bark is separated from the wood and air-dried.

Yield

A good mangrove stand can have an annual wood productivity of 10–20(–25) m³ per ha for all species. The yield of bark per ha from Bruguiera gymnorhiza is unknown.

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Handling after harvest

Chopped bark can be used directly in the tannery or the tannin can be extracted by boiling the bark in large vessels and evaporating down to a solid brown-black mass, called ‘cutch’. Boiled bark or dissolved cutch can both be used for dyeing textile fibres and leather in various shades of orange to reddish brown (without mordant or with an alum mordant), and in grey to black if an iron mordant is used.

Genetic resources and breeding

Bruguiera gymnorhiza is widespread and not yet in direct danger of genetic erosion. In eastern tropical Africa, including the Indian Ocean islands, about 10,000 km² mangrove vegetation is present. Tanzania, Mozambique and Madagascar are the countries with largest mangrove areas. About 25 areas are protected, but in many regions mangroves are threatened. They are over-exploited for timber or are cleared to make way for rice or shrimp farms, salt pans and urban development. These ecologically important habitats are also threatened by untreated waste discharged into rivers, industrial pollution and pesticides contained in run-off from farms. Dams constructed in rivers that flow into mangrove habitats have decreased the flow of water causing the salt content to increase to unnaturally high levels. Mangroves are also vulnerable to natural stresses such as river floods, deposition of sand and sediments, and rising sea levels. The decline of mangrove forests along the East African coast is mainly due to over-exploitation for charcoal, firewood, timber, dyeing and tanning materials without replanting. All these issues should be included in future mangrove management and reforestation plans.

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Prospects

The use of Bruguiera gymnorhiza bark for tanning may only remain important locally. The possibilities to only use the leaves and small branches as tannin and dye sources for local uses without damaging or cutting down the trees should be considered. In a broader perspective, the main issue is a rationalized use of mangrove forests. This will mean changes to present approaches in mangrove management. Problems to overcome are the lack of community input into management approaches, high levels of poverty within indigenous coastal communities, a general lack of awareness of the true value of mangroves, and over-utilization for charcoal, firewood, timber, tanning and dyeing materials. There has been no reforestation done in areas where mangroves have been exploited. Management policies have been introduced to control and prohibit destruction of mangrove forests, but there are few or no means available for their implementation. Knowledge of many aspects of mangrove ecosystems needs to be improved. Proper techniques for natural and artificial regeneration need to be developed, and more information is needed on growth and development.

Major references

• Coates Palgrave, K., 1983. Trees of southern Africa. 2nd Edition. Struik Publishers, Cape Town, South Africa. 959 pp.
• Rudjiman, 1991. Bruguiera gymnorhiza (L.) Savigny. In: Lemmens, R.H.M.J. & Wulijarni-Soetjipto, N. (Editors). Plant Resources of South-East Asia No 3. Dye and tannin producing plants. Pudoc, Wageningen, Netherlands. pp. 53–55.
• Saberi Othman, 1998. Bruguiera Lamk. In: Sosef, M.S.M., Hong, L.T. & Prawirohatmodjo, S. (Editors). Plant Resources of South-East Asia No 5(3). Timber trees: Lesser-known timbers. Backhuys Publishers, Leiden, Netherlands. pp. 122–125.
• Taylor, M., Ravilious, C. & Green, E.P., 2003. Mangroves of East Africa. UNEP - World Conservation Monitoring Centre (WCMC), Cambridge, United Kingdom. 24 pp.
• Torre, A.R. & Gonçalves, A.E., 1978. Rhizophoraceae. In: Launert, E. (Editor). Flora Zambesiaca. Volume 4. Flora Zambesiaca Managing Committee, London, United Kingdom. pp. 81–99.

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Other references

• Arènes, J., 1954. Rhizophoracées (Rhizophoraceae). Flore de Madagascar et des Comores (plantes vasculaires), familles 147–151. Firmin-Didot et cie., Paris, France. 42 pp.
• Beentje, H.J., 1994. Kenya trees, shrubs and lianas. National Museums of Kenya, Nairobi, Kenya. 722 pp.
• Boonkerd, T. & Chan, H.T., 1997. Bruguiera cylindrica (L.) Blume. In: Faridah Hanum, I. & van der Maesen, L.J.G. (Editors). Plant Resources of South-East Asia No 11. Auxiliary plants. Backhuys Publishers, Leiden, Netherlands. pp. 76–78.
• Chan, H.T. & Boonkerd, T., 1997. Bruguiera sexangula (Lour.) Poiret. In: Faridah Hanum, I. & van der Maesen, L.J.G. (Editors). Plant Resources of South-East Asia No 11. Auxiliary plants. Backhuys Publishers, Leiden, Netherlands. pp. 78–79.
• Decary, R., 1946. Plantes et animaux utiles de Madagascar. Annales du Musée Colonial de Marseille, 54e année, 6e série, 4e volume, 1er et dernier fascicule. 234 pp.
• Friis, I., 1993. Rhizophoraceae. In: Thulin, M. (Editor). Flora of Somalia. Volume 1. Pteridophyta; Gymnospermae; Angiospermae (Annonaceae-Fabaceae). Royal Botanic Gardens, Kew, Richmond, United Kingdom. pp. 254–258.
• Gonçalves, A.E. & Torre, A.R., 1979. Rhizophoraceae. In: Mendes, E.J. (Editor). Flora de Moçambique. No 67. Junta de Investigações Científicas do Ultramar, Lisbon, Portugal. 21 pp.
• Gurib-Fakim, A., Guého, J. & Bissoondoyal, M.D., 1997. Plantes médicinales de Maurice, tome 3. Editions de l’Océan Indien, Rose-Hill, Mauritius. 471 pp.
• Hou, D., 1958. Rhizophoraceae. In: van Steenis, C.G.G.J. (Editor). Flora Malesiana, Series 1, Volume 5. pp. 429–493.
• Lewis, J., 1956. Rhizophoraceae. In: Turrill, W.B. & Milne-Redhead, E. (Editors). Flora of Tropical East Africa. Crown Agents for Oversea Governments and Administrations, London, United Kingdom. 20 pp.
• Porter, L.J., 1994. Flavans and proanthocyanidins. In : Harborne, J.B. (Editor). The flavonoids. Advances in research since 1986. Chapman & Hall, London, United Kingdom. pp. 23–55.
• Tomlinson, P.B., 1986. The botany of mangroves. Cambridge University Press, Cambridge, United Kingdom. 413 pp.
• Watt, J.M. & Breyer-Brandwijk, M.G., 1962. The medicinal and poisonous plants of southern and eastern Africa. 2nd Edition. E. and S. Livingstone, London, United Kingdom. 1457 pp.
• Williams, R.O., 1949. The useful and ornamental plants in Zanzibar and Pemba. Zanzibar, Tanzania. 497 pp.

Afriref references

Sources of illustration

• Saberi Othman, 1998. Bruguiera Lamk. In: Sosef, M.S.M., Hong, L.T. & Prawirohatmodjo, S. (Editors). Plant Resources of South-East Asia No 5(3). Timber trees: Lesser-known timbers. Backhuys Publishers, Leiden, Netherlands. pp. 122–125.

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Author(s)

•	V.N. Mainga World Agroforestry Centre (ICRAF), P.O. Box 30677, Nairobi, Kenya

Based on PROSEA 3: ‘Dye and tannin-producing plants’.

Editors

•	P.C.M. Jansen PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
•	D. Cardon CNRS, CIHAM-UMR 5648, 18, quai Claude-Bernard, 69365 Lyon, Cedex 07, France

General editors

•	R.H.M.J. Lemmens PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
•	L.P.A. Oyen PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Photo editor

•	E. Boer PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Correct citation of this article

Mainga, V.N., 2005. Bruguiera gymnorhiza (L.) Savigny. [Internet] Record from PROTA4U. Jansen, P.C.M. & Cardon, D. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands. <http://www.prota4u.org/search.asp>. Accessed .

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