Tetrameles (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Tetrameles R. Br.

Protologue: Denham & Clapperton, Narr. travels Africa: 230 (1826).

Family: Datiscaceae

Chromosome number: x= c. 32; T. nudiflora: n= c. 32

Vernacular names

• Binung (trade name)
• Tetrameles (En)
• Indonesia: binong (Sundanese), kayu tabu (Palembang, Sumatra), winong (Javanese)
• Malaysia: mengkundor (Peninsular)
• Burma (Myanmar): baing, sawbya, thitpok
• Laos: phoung, 'sa phoung
• Thailand: bueng (northern), ka phong (central, peninsular), som phong (south-eastern)
• Vietnam: dăng, daoleo, thung.

Origin and geographic distribution

Tetrameles is monotypic and occurs from Sri Lanka and India to Burma (Myanmar), Indo-China, southern China, Thailand, northern Peninsular Malaysia, Sumatra (extreme north and extreme south), Java, Sulawesi, the Lesser Sunda Islands, New Guinea and northern Australia (Queensland). The only species is T. nudiflora R. Br. (synonyms: T. grahamiana Wight, T. horsfieldii Steud.).

Uses

Tetrameles wood is used for temporary construction, panelling, partitioning, ceiling boards, cheap planking, weatherboard, mouldings, floats, dugout canoes, packing boxes, tea-chests and matchboxes. It is comparatively often used in the production of low-grade veneer, plywood and blockboard, and for the manufacture of hardboard and wrapping and writing paper. It is also rated as highly suitable for cement-bonded wood-wool board manufacture and for some uses it may prove to be a suitable substitute for "balsa" (Ochroma pyramidale (Cav. ex Lamk) Urban).

In Cambodia the bark has been applied medicinally as a laxative and diuretic, and in decoctions taken for rheumatism, oedema, ascites and jaundice.

Production and international trade

In the past large amounts of Tetrameles wood were traded in and exported from India and Indo-China, but supplies have become limited. In the 1970s the average annual export from Thailand was about 5000 m³, from Assam, India about 2000 t and from the Andaman Islands about 600 t. In 1996 Papua New Guinea exported about 5500 m³of Tetrameles logs at an average free-on-board (FOB) price of US$ 99/m³.

Properties

T. nudiflora yields a lightweight hardwood with a density of 250-420 kg/m³at 15% moisture content. Heartwood pale brown to grey-brown, occasionally with an olive-green tinge, darkening to yellow-brown upon exposure, not clearly differentiated from the pale yellow sapwood; grain interlocked, occasionally straight; texture moderately coarse to coarse and even; wood with broad stripe figure on quarter-sawn faces due to the alternating or interlocked grain. Growth rings indistinct, occasionally indicated by closer spacing of vessels; vessels medium-sized to moderately large, solitary and in radial multiples of 2-3, open, tyloses sometimes present; parenchyma moderately abundant, sometimes bright yellow in colour, paratracheal vasicentric to aliform; rays very fine to medium-sized; fine ripple marks sometimes distinct resulting from storied fibres.

Shrinkage upon seasoning is low to moderate; sawn timber air dries well but end-splitting and surface checking may occur. Kiln drying can also be satisfactorily applied. The wood is soft and very weak, but strong in relation to its density. The wood should be converted rapidly to avoid blue stain and insect attack; it can be easily sawn and planed to a fairly smooth surface, but it does not polish well. It peels easily but plywood is not very attractive and it is generally used for core stock. The wood is non-durable and in a graveyard test in Thailand the average service life of test stakes was 1.9 years. Preservative treatment under pressure is very easy, the sapwood showing an absorption of CCA solution of 171 kg/m³and the heartwood of 208 kg/m³. The wood is susceptible to termite and ambrosia beetle attack. The sapwood is susceptible to Lyctus.

The gross energy value is about 20 670 kJ/kg. The mean fibre length from Indonesian material is 1.148 mm.

See also the tables on microscopic wood anatomy and wood properties.

Botany

• A deciduous, dioecious, medium-sized to large tree up to 50 m tall; bole columnar, branchless for up to 35 m, up to 120(-200) cm in diameter, often fluted or with steep buttresses up to 5 m high; bark smooth, often pustular, sometimes hoop-marked, silvery grey to brownish, inner bark finely fibrous, ochre.
• Leaves arranged spirally, simple, dentate to nearly entire, palmately veined, rounded to cordate at base, exstipulate.
• Flowers in a terminal, fasciculate, pendent, simple or little branched spike (male) or panicle (female); petals absent. Male flower 4-merous; calyx with a short tube; stamens 4, inserted on the cup-shaped receptacle. Female flower 4-5-merous; base of calyx connate with ovary; ovary inferior, 1-locular with many ovules, styles opposite the calyx lobes, with a groove and oblique stigmatic apex.
• Fruit a globular capsule with an apical pore between the persistent styles.
• Seed narrowly oblong.
• Seedling with epigeal germination; cotyledons emergent, leafy; hypocotyl elongated; all leaves arranged spirally.

The mean annual increment of 10-year-old trees planted in West Java was 1 m in height and 1.7 cm in diameter, whereas that of 6-year-old trees planted at 550 m altitude in East Java was 2.2 m in height and 3.0 cm in diameter. In Peninsular Malaysia most trees are leafless in February-April, in Java in September-December during the rainy season. Flowers appear when the tree is leafless and are frequently visited by bees. Maturation of the fruits takes 1-2 months. The small seeds are probably dispersed by wind.

Ecology

T. nudiflora is found scattered but is fairly common in primary or secondary, deciduous forest up to 500(-1000) m altitude. It is restricted to regions with a more or less pronounced dry season. It is common in teak forest and prefers dry, sandy to rocky soils; in Papua New Guinea it prefers limestone.

Silviculture

T. nudiflora can be propagated by seed. In an uncleaned seedlot about 2 185 000 dry seeds/kg have been counted. Seeds should be sown within 2 weeks after collection as they rapidly lose their viability. The tree is not resistant to fire.

Genetic resources and breeding

Supplies of T. nudiflora timber have dwindled due the high demand for lightweight timber for cases. Whether this affects the genetic resources of T. nudiflora in its natural distribution area is uncertain but not unlikely.

Prospects

Because of its fast growth, the relative ease of handling and planting and the demand for lightweight timber T. nudiflora is a potentially important plantation tree.

Literature

40, 125, 163, 218, 260, 267, 300, 336, 340, 341, 348, 377, 403, 405, 406, 427, 436, 460, 464, 478, 536, 591, 745, 765, 861, 933, 1038, 1052, 1169, 1177, 1199, 1221, 1242.

E. Boer & M.S.M. Sosef