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Sonneratia alba Sm.

Protologue
Rees, Cycl. 33(I): Sonneratia no. 2 (1816).
Family
Sonneratiaceae (APG: Lythraceae)
Chromosome number
n = 11, 12
Vernacular names
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.
Uses
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.
Properties
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 9–12% tannin based on dry weight.
Botany
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 3–15 mm long; blade elliptical to ovate, 3–13 cm Χ 2–9 cm, cuneate at base, rounded or notched at apex, leathery, pinnately veined with 11–14 pairs of lateral veins. Flowers solitary or 3 together at the apex of twigs, bisexual, regular, 6–8-merous; calyx tube c. 1.5 cm long, thick, leathery, persistent, lobes 1–2 cm long; petals strap-shaped, 1–2 cm long, caducous; stamens numerous, showy, white; ovary superior, 12–20-celled, style 4–6 cm long, slender. Fruit a depressed-globose berry, 2–3 cm Χ 2.5–4.5 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 Rauh’s 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.
Ecology
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.
Management
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 1–2% worldwide.
Prospects
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.
Major references
• Boer, E. & Lemmens, R.H.M.J., 1998. Sonneratia L. f. 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. 529–532.
• Bosire, J.O., Dahdouh-Guebas, F., Walton, M., Crona, B.I., Lewis III, R.R., Field, C., Kairo, J.G. & Koedam, N., 2008. Functionality of restored mangroves: a review. Aquatic Botany 89(2): 251–259.
• Duke, N.C. & Jackes, B.R., 1987. A systematic revision of the mangrove genus Sonneratia (Sonneratiaceae) in Australasia. Blumea 32: 277–302.
• Fernandes, A., 1978. Sonneratiaceae. In: Launert, E. (Editor). Flora Zambesiaca. Volume 4. Flora Zambesiaca Managing Committee, London, United Kingdom. pp. 327–329.
• Kairo, J.G., Dahdouh-Guebas, F., Bosire, J. & Koedam, N., 2001. Restoration and management of mangrove systems: a lesson for and from the East African region. South African Journal of Botany 67: 383–389.
Other references
• Alongi, D.M., 2008. Mangrove forests: Resilience, protection from tsunamis, and responses to global climate change. Estuarine, Coastal and Shelf Science 76(1): 1–13.
• Dahdouh-Guebas, F., Mathenge, C., Kairo, G. & Koedam, N., 2000. Utilization of mangrove wood products around Mida Creek (Kenya) amongst subsistence and commercial users. Economic Botany 54(4): 513–527.
• Ellison, J.C., 1998. Impacts of sediment burial on mangroves. Marine Pollution Bulletin 37(8–12): 420–426.
• FAO, 2007. Mangroves of Africa 1980-2005: Country Reports. Forest Resources Assessment Programme, Working Paper 135, Rome, Italy. 155 pp.
• Nshubemuki, L., 1993. Forestry resources in Tanzania's wetlands: concepts and potentials. In: Kamukala, G.L. & Crafter, S.A. (Editors). Wetlands of Tanzania. Proceedings of a seminar on wetlands of Tanzania. IUCN Wetlands Programme, Nairobi , Kenya. pp. 37–48.
• Schatz, G.E., 2001. Generic tree flora of Madagascar. Royal Botanic Gardens, Kew, Richmond, United Kingdom. 477 pp.
• Shi, S., Huang, Y., Tan, F., He, X. & Boufford, D.E., 2000. Phylogenetic analysis of the Sonneratiaceae and its relationship to Lythraceae based on ITS sequences of nrDNA. Journal of Plant Research 113: 253–258.
• Williams Sangai, G.R., 1968. Sonneratiaceae. In: Milne-Redhead, E. & Polhill, R.M. (Editors). Flora of Tropical East Africa. Crown Agents for Oversea Governments and Administrations, London, United Kingdom. 4 pp.
Author(s)
• C.H. Bosch
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands


Editors
• R.H.M.J. Lemmens
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
• D. Louppe
CIRAD, Dιpartement Environnements et Sociιtιs, Cirad es-dir, Campus international de Baillarguet, TA C-DIR / B (Bβt. C, Bur. 113), 34398 Montpellier Cedex 5, France
• A.A. Oteng-Amoako
Forestry Research Institute of Ghana (FORIG), University P.O. Box 63, KNUST, Kumasi, Ghana
Associate editors
• E.A. Obeng
Forestry Research Institute of Ghana (FORIG), University P.O. Box 63, KNUST, Kumasi, Ghana
Photo editor
• G.H. Schmelzer
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

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 d’œuvre 2. [CD-Rom]. PROTA, Wageningen, Netherlands.
Sonneratia alba


Sonneratia alba


Sonneratia alba


wood in transverse section


wood in tangential section


wood in radial section