Prota 7(2): Timbers/Bois duvre 2
Rees, Cycl. 33(I): Sonneratia no. 2 (1816).
Sonneratiaceae (APG: Lythraceae)
n = 11, 12
Red-brown mangrove (En). Mlilana, mpia (Sw).
Origin and geographic distribution
Sonneratia alba is extremely widespread. It occurs along the east coast of tropical Africa from Somalia south to Mozambique and in Comoros, Mayotte, the Seychelles and Madagascar. It is also found throughout tropical Asia, and in northern Australia, Vanuatu and New Caledonia.
The wood of Sonneratia alba is used in Kenya and Tanzania for carpentry, canoes, boat ribs, paddles, masts, floats, and window and door frames. It is further used as firewood and for charcoal production. In Madagascar the wood is preferred for making paddles. In tropical Asia the wood is used for house building, ship building, piles of bridges, sleepers, paving blocks, flooring, furniture and sporting goods. Sulphate pulp of the wood is suitable for making paper.
The sour fruits are eaten raw or cooked and used to make vinegar. Leaves are used for camel fodder in Kenya. The bark is locally used as a brownish dye and for tanning leather and fishing nets.
Production and international trade
In tropical Africa there is no significant trade in Sonneratia timber. For Asia trade statistics are not readily available and refer to timber of all Sonneratia species together. In 1992 about 5100 m³ of logs and 1700 m³ of sawn timber were exported from Sabah at prices of about US$ 73/m³ and US$ 150/m³, respectively. Very small amounts of Sonneratia timber are exported from Papua New Guinea.
The heartwood is brown to reddish brown and distinctly demarcated from the paler sapwood. The wood is moderately heavy, hard and durable. It contains small amounts of salt, making it resistant to wood borers. It corrodes metal and therefore special nails and screws are needed.
The wood is of moderate quality for firewood. Although it produces a lot of heat, it produces much ash and salt. The bark of Sonneratia alba contains 912% tannin based on dry weight.
Evergreen shrub or small tree up to 15(20) m tall; bole often crooked and fluted at base, without buttresses, surrounded by aerial roots arising vertically from long horizontal roots; bark surface initially smooth, greyish, becoming irregularly fissured and dark grey-brown; twigs distinctly jointed above the nodes and 4-angled. Leaves opposite, simple and entire; stipules absent; petiole 315 mm long; blade elliptical to ovate, 313 cm Χ 29 cm, cuneate at base, rounded or notched at apex, leathery, pinnately veined with 1114 pairs of lateral veins. Flowers solitary or 3 together at the apex of twigs, bisexual, regular, 68-merous; calyx tube c. 1.5 cm long, thick, leathery, persistent, lobes 12 cm long; petals strap-shaped, 12 cm long, caducous; stamens numerous, showy, white; ovary superior, 1220-celled, style 46 cm long, slender. Fruit a depressed-globose berry, 23 cm Χ 2.54.5 cm, indehiscent, crowned by the style base, many-seeded. Seeds irregularly angular, c. 12 mm long. Seedling with epigeal germination; hypocotyl elongated; cotyledons emergent.
Sonneratia alba trees develop according to Rauhs architectural model, characterized by a monopodial trunk which grows rhythmically and so develops tiers of branches. It flowers at night and petals and stamens drop within hours from anthesis.
Sonneratia comprises about 5 species.
Sonneratia alba is found at the seaward edge of mangrove because it does not tolerate wide fluctuations in salt concentration. A tidal range of at least 1 m is necessary and it grows along seashores and at the mouth of tidal creeks on sandy, rocky or muddy soils, and also on coral terraces. It may act as a pioneer, colonizing newly formed sandy mud flats in sheltered situations. It is often gregarious, but usually does not form dense stands.
Sonneratia alba can be propagated by seed as well as by air-layering. It is less suited for replanting on sites where sedimentation is high as the sediment will cover the pneumatophores and hence kill the plants.
Genetic resources and breeding
Sonneratia alba is widespread and common in many regions and does not seem vulnerable, although the rate of destruction of mangrove habitats is alarming with an estimated annual loss of 12% worldwide.
In mangrove forest Bruguiera and Rhizophora are usually economically more important timber species than Sonneratia. Replanting in damaged and logged mangrove vegetations is usually done with Avicennia and Rhizophora species and thus the importance of Sonneratia for its wood is likely to decrease. However, it has very good potential as a valuable source of raw material for kraft pulp which warrants serious consideration.
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Correct citation of this article:
Bosch, C.H., 2010. Sonneratia alba Sm. In: Lemmens, R.H.M.J., Louppe, D. & Oteng-Amoako, A.A. (Editors). Prota 7(2): Timbers/Bois duvre 2. [CD-Rom]. PROTA, Wageningen, Netherlands.
wood in transverse section
wood in tangential section
wood in radial section