Tristaniopsis (PROSEA)
Introduction |
Tristaniopsis Brongn. & Gris
- Protologue: Bull. Soc. Bot. France 10: 371 (1863).
- Family: Myrtaceae
- Chromosome number: x= unknown;T. laurina(J.E. Smith) Peter G. Wilson & J.T. Waterh.: 2n= 22
Vernacular names
- Brunei: selan
- Indonesia: pelawan (general)
- Malaysia: keruntum, pelawan (general), melaban, selunsur (Sarawak)
- Papua New Guinea: Papua New Guinea swamp box, swamp mahogany
- Philippines: malabayabas (Filipino). Burma (Myanmar): duakyat
- Thailand: tamsao-nu.
Origin and geographic distribution
Tristaniopsis is a fairly large genus of about 45 species which occur from Burma (Myanmar) and Thailand, throughout the Malesian region (except central and eastern Java and the Lesser Sunda Islands), to eastern Australia and New Caledonia. About 20 species occur within Malesia.
Uses
The hard and durable wood of Tristaniopsis is used for heavy constructional work, e.g. for posts and beams for house and bridge construction, wharves and jetties, sleepers, poles, piling, heavy duty flooring, exterior decking, tool handles, mauls and mallets, spokes and wheels, pulleys, bearings, rollers, saw guide blocks, bowling balls, transmission poles and stakes for pepper support. It is sometimes used for paddles, rice pestles, and for high-quality firewood or charcoal.
In Sulawesi an unknown species of Tristaniopsis has been planted as a fire-break in Pinus merkusii Jungh. & de Vriese plantations.
Production and international trade
Export of Tristaniopsis has been mainly between Asian Pacific countries, the main consumer being Australia. It is occasionally exported to Japan. In Papua New Guinea Tristaniopsis timber is traded together with that of Lophostemon and Welchiodendron as "Papua New Guinea swamp box" of which only 150 m3was exported at an average free-on-board (FOB) price of US$ 101/m3in 1996.
Properties
Tristaniopsis yields a heavy hardwood with a density of 865-1250 kg/m3at 15% moisture content. Heartwood pink-brown, red-brown or purple-grey-brown, only occasionally distinct from the paler sapwood; grain interlocked, sometimes wavy; texture fine and even; wood sometimes with some silver grain. Growth rings indistinct, larger vessels with tendency to align in concentric rings; vessels rather variable in size, from very small to medium-sized, almost exclusively solitary, usually in oblique arrangement, with reddish gum-like deposits or blocked by tyloses; parenchyma sparse, paratracheal and apotracheal diffuse tending to short tangential bands, hardly visible with a hand lens; rays very fine, visible with a hand lens; ripple marks absent.
Shrinkage of the wood upon seasoning is variable, from moderate to very high. It takes about 5 months to air dry boards 40 mm thick during which time the wood is subject to warping (particularly back-sawn boards), distortion and surface checking (not severe relative to its density). Partial air drying to 30% moisture content before kiln drying and a final reconditioning treatment is recommended. In Malaysia kiln-drying schedule D is recommended. The wood is very hard, very strong and tough. It is fairly difficult to work due to its hardness and high silica content. Tool edges blunt rapidly and sawing is especially difficult. The wood can be planed to a relatively smooth surface, although a reduced cutting angle of 15-20may be necessary. It turns excellently. Pre-boring is necessary before nailing. Bending of T. decorticata is rated as fair for boards 2.5 cm thick and very good for boards 0.3 cm thick. The wood is durable to extremely durable when exposed to the weather or in contact with the ground. It is resistant to termite and marine borer attack, whereas the sapwood is non-susceptible to Lyctus . The heartwood is extremely resistant to impregnation.
See also the tables on microscopic wood anatomy and wood properties.
Botany
Shrubs or small, medium-sized to large trees up to 45 m tall; bole up to 70(-120) cm in diameter, buttresses absent; bark surface smooth, often peeling off in large, spiral, scroll-like pieces, usually accumulating round the base of the trunk, orange-brown to pinkish-grey, inner bark whitish or yellowish. Leaves alternate, simple, entire, with glandular dots and an intramarginal vein; stipules absent. Inflorescence axillary, cymose. Flowers 5-merous; calyx lobes persistent; petals free, white or yellow; stamens numerous, fused into fascicles opposite the petals; ovary half-inferior to superior, (2-)3-locular with numerous pendulous ovules, style filiform with a capitate stigma. Fruit a loculicidal capsule, exserted from the hypanthium, hemispherical in the upper part, with a distinctive column at the centre of the dehisced fruit. Seed usually winged, with a straight embryo and convolute or obvolute, reniform cotyledons. Seedling with epigeal germination; cotyledons leafy, 2-lobed; leaves convolute.
Mass-flowering with intervals of several years has been reported for T. micrantha in the Philippines. It has been suggested that sudden changes in temperature may initiate flowering. The flowering trees are mostly leafless. The fruits burst open with some force, slightly scattering the seeds. After the fruits burst, young leaves develop. Young leaves are often pink, old withered leaves red.
Recent studies revealed that Tristania sensu lato is heterogeneous and it was split into 5 genera: Lophostemon (4 species), Ristantia (3 species), Tristania sensu stricto (1 species, restricted to Australia), Welchiodendron (1 species), and Tristaniopsis (comprising the majority of species, including all western Malesian ones formerly referred to as Tristania spp.). Tristaniopsis is distinguished from the other genera particularly by the combination of its alternate leaves, its fruit exserted from the hypanthium and its winged seeds.
Ecology
Tristaniopsis species occur in many different types of lowland to lower montane forest up to 1300 m altitude, often along rivers or near the coast, but also in rocky locations. They are often common but do not occur gregariously. Some species, such as T. whiteana , grow especially on landslides and open patches along streams, and in secondary forest and are evidently efficient colonizers. They often grow together with Cratoxylum species.
Silviculture Tristaniopsis may be propagated by seed. The number of dry seeds of T. obovata is about 1.4 million. In a germination trial seed of T. merguensis germinated for 70-85% in 13-22 days. In Java Tristaniopsis has been planted above 1000 m altitude.
Genetic resources and breeding
Tristaniopsis trees do not seem to be subject to extensive logging as the timber is mainly used locally and has no great economic importance. The supply in the forest still seems to be considerable for many species.
Prospects
As the demand for very hard wood for specialty use is increasing in Europe and a fair supply can be generated from parts of Sarawak and Indonesia, Tristaniopsis may be expected to gain importance as an export timber.
Literature
1, 151, 154, 162, 163, 209, 218, 235, 260, 267, 296, 300, 302, 360, 436, 487, 536, 775, 780, 829, 831, 861, 934, 1023, 1040, 1221, 1230, 1239, 1242, 1274.