Pometia J.R. Forster & J.G. Forster
- Protologue: Charact. Gen. Pl.: 55, t. 55 (1775).
- Family: Sapindaceae
- Chromosome number: x= unknown
Kasai: medium-weight timber, particularly Pometia pinnata J.R. Forster & J.G. Forster.
- taun, matoa, megan (general)
- Indonesia: leungsir (Java), tawan (Moluccas), ihi mendek (Irian Jaya)
- Malaysia: sibu (Sarawak)
- Papua New Guinea: taun
- Philippines: malugai (Tagalog)
- Burma: paga-nyet-su ava
- Laos: chieng dong, kwaang
- Thailand: sai (Yala), daengnam (northern)
- Vietnam: trường mật, sâng, mắc ken.
Origin and geographic distribution
Pometia consists of 2 species and is native from Sri Lanka and the Andaman Islands, throughout South-East Asia, towards Fiji and Samoa. It is rare in mainland South-East Asia and in Taiwan. Kasai is sometimes cultivated for its fruits within its natural area of distribution.
Kasai is a good general-purpose wood for interior construction. The wood is suitable for domestic flooring, mouldings, joinery, ship and boat building, spars, tool handles, agricultural and sporting implements, interior trimming, blockboard, and tight cooperage. It is well accepted for making boxes and crates. On the export market kasai is recommended for joinery (windows, solid doors, framing, weather-boarding) and flooring for both light and medium pedestrian traffic. In outdoor constructions contact with the ground must be prevented as the wood is then not durable. The timber is used for furniture and cabinet work but must be dried to a sufficiently low moisture content. It is suitable for hardboard and particle board and as pulpwood. The wood makes a good-quality veneer which has potential to be used as decorative veneer and is very suitable for core and outer layers of plywood. Kasai may produce a good charcoal for domestic or industrial purposes.
The arillode of the fruit of trees cultivated for fruit production is eaten fresh and tastes like rambutan; it is of local interest only, e.g. in the Sentani Lake region of Irian Jaya, where especially purplish fruits are preferred and selected. The roasted seeds of kasai are also edible. A decoction of the leaves or bark is used medicinally against fever and sores. In Papua New Guinea kasai is sometimes planted in a cycle of shifting cultivation and its leaves are used as a mulch and green manure in yam cultivation.
Production and international trade
Although kasai is frequently mentioned as a promising timber for export, little information is available on harvested and traded volumes. In 1978 the export of logs from Irian Jaya was 35 000 m3 with a value of US$ 1.4 million. In 1979 the export increased considerably to 194 000 m3 with a value of US$ 17 million. Export from Irian Jaya was mainly to Japan, Taiwan and Korea. It is also exported in fairly large amounts to Japan from Papua New Guinea and the Solomon Islands. In Papua New Guinea kasai is ranked in MEP (Minimum Export Price) group 1, and fetched a minimum export price of US$ 75/m3 for saw logs in 1992. Considerable standing volumes are present especially in the eastern part of the area of distribution. Small amounts of kasai timber are exported from Sabah: in 1992 340 m3 of logs and 70 m3 of sawn timber with a total value of US$ 36 000.
Kasai is a medium-weight timber; it is not hard, and faintly resembles meranti and mahogany. The heartwood is light to dark red, medium dark red-brown, or sometimes purplish, with a glossy surface; radial and tangential sections sometimes show dark coloured ribbons. The sapwood is pink or buff-coloured, on average 3 cm wide, and not always well demarcated from the heartwood.
Wood properties of kasai vary widely over the various provenances and regions. Hillside trees are better than lowland trees in wood quality, and wood near the heart of the log is reported to be lighter, softer and less strong than the outer wood. The density of kasai from Malaysia is 735-915 kg/m3 at 15% moisture content, but that from Papua New Guinea is less: 625-700 kg/m3 at 12% moisture content. The overall density range is 390-860 kg/m3 at 12% moisture content. The grain of the wood is straight or slightly interlocked, texture rather coarse but even.
Wood tested in Malaysia at 21% moisture content showed the following figures for mechanical properties: modulus of rupture 106 N/mm2, modulus of elasticity 17 000 N/mm2, compression parallel to grain 49-54 N/mm2. Tests in Indonesia at 15% moisture content gave the following figures: modulus of rupture 77-100 N/mm2, modulus of elasticity 8900-14 000 N/mm2, compression parallel to grain 37-57 N/mm2, shear 7-11 N/mm2, cleavage 50-64 N/mm radial and 53-69 N/mm tangential, Janka side hardness 3870-4320 N and Janka end hardness 4910-6350 N. Wood tested in the Philippines at 12% moisture content had a modulus of rupture of 166 N/mm2, modulus of elasticity of 13 900 N/mm2, compression parallel to grain of 60 N/mm2, and Janka side hardness of 6440 N. Wood tested in Papua New Guinea at 12% moisture content had a modulus of rupture of 105-110 N/mm2, modulus of elasticity of 12 800-14 900 N/mm2, compression parallel to grain of 56-60 N/mm2 and Janka side hardness of 4700-6500 N. Figures from tests in Thailand are comparable, although the modulus of rupture is slightly less: 93 N/mm2 at 12% moisture content.
The rates of shrinkage are medium to high: for Malaysian wood 2.8% radial and 3.5% tangential from green to 15% moisture content, and for wood from Papua New Guinea 3.5% radial and 6.6% tangential from green to 12% moisture content. Kasai usually seasons slowly, with considerable degrade unless handled with care. Collapse mostly occurs during seasoning. Twisting, splitting and surface checking can be prevented if kasai is carefully seasoned and close attention is paid to stacking technique; bowing and end checking will be minimal. Slight to moderate collapse may occur during kiln drying from the green condition. Weighting of stacks at the outset of drying and close spacing of stickers is beneficial. When the timber is kiln dried, a reconditioning treatment may be necessary if considerable collapse or twist develops, otherwise a high humidity treatment should be applied at the completion of drying to relieve stresses, although response to reconditioning can be variable. Even when properly dried, the wood is rather unstable under varying relative air humidity conditions such as those found in temperate zones.
As a rule, kasai is easy to machine when green but slightly difficult to resaw and cross cut when air dried, with little blunting effect on saws (the wood contains no silica), producing fair to excellent surfaces. It planes well with a slight tendency to chip at interlocked grain junctions and it sands to a fine finish. It polishes well to a high finish and takes paint quite satisfactorily. Kasai turns easily with little or no burning. The timber can be nailed without difficulty although occasional splitting does occur, and it has good nail-holding capacity; it glues well, is readily bored and screws well. The steam bending properties are generally good. Fine dust may cause irritation to mucous membranes when working with dried material; an effective dust-extractor is strongly advised. Kasai is moderately easy to rather difficult to cut into smooth, tight veneer of uniform thickness at a cutting temperature of about 70° C; it dries flat and split-free with medium shrinkage. For plywood production the wood can be glued very satisfactorily with modern types of glue and it shows a good bonding strength. However, gluing of veneer is reported as rather difficult in Indonesia.
Kasai heartwood is rated as moderately durable to non-durable. Stake tests show a service life in contact with the ground of up to 5 years under tropical conditions; tests in Indonesia showed a service life of 2-3.5 years. Based on laboratory tests carried out in the Netherlands, the heartwood of material from Irian Jaya was found to be moderately durable to nondurable in contact with the ground under temperate conditions. The heartwood is rated as rarely susceptible to powder-post beetles, as liable to brown stain and as susceptible to attack by dry-wood termites. Timber is only moderately resistant to termite attack and is not resistant to marine borer attack. The air-dried heartwood is classified as very resistant to impregnation of preservatives, the sapwood is moderately resistant. Impregnation with CCA preservative may vary considerably and is classified as moderately difficult to extremely difficult. Using the open tank method, the wood absorbs 5.6 kg/m3 of a 10% BFCA solution after 7 hours.
The wood contains saponin, as does the fruit, and may produce slight foam in water. Kasai wood (from Indonesia) contains 57% cellulose, 20% lignin, 20% pentosan, 0.8% ash and no silica. The solubility is 2.5% in alcohol-benzene, 0.4% in cold water, 3.4% in hot water and 12.6% in a 1% NaOH solution. The energy value is 19 760 kJ/kg.
- Medium-sized to fairly large evergreen or shortly deciduous, monoecious trees up to 40(-50) m tall with a straight (New Guinea) or curved or sinuous bole, usually branchless for 13-22 m and up to 100(-140) cm in diameter, often prominently buttressed; buttresses sharp, up to 5.5 m tall and spreading up to 3.5 m from the bole; bark brownish-grey to reddish-brown, shedding small, pockmarked, thick flakes, with occasionally abundant red gum; branchlets grooved or smooth, glabrous, innovations red or purple, densely brown-fulvous hairy.
- Leaves paripinnate, with (3-)4-13 pairs of leaflets, the lowest pair often stipule-like, the rachis up to 1 m or even longer; leaflets leathery or firmly herbaceous, often asymmetrical, on average 12-30 cm × 4-10 cm, margin smooth or dentate, secondary veins nearly parallel, surfaces smooth.
- Inflorescence a terminal or rarely axillary panicle of about 15-60 cm long.
- Flowers functionally unisexual, actinomorphic, 5-merous, small; petals cream-white, disk annular.
- Fruit a schizocarp, mostly simple by abortion, smooth, ellipsoid, up to 3.5 cm × 3 cm, coloured in variations of yellow, red, purple or brown, pericarp 2-7 mm thick.
- Seed half to three-quarters of the size of the fruit, covered by an arillode of up to 4 mm thick, shiny brown or red-brown.
- Seedling with epigeal germination; cotyledons slightly sagittate; first pair of leaves subopposite, imparipinnate with 5 serrate leaflets, transition to paripinnate taking place in the third and fourth leaf.
- Heartwood light to dark red, medium dark red-brown, sometimes purplish, sometimes with dark coloured ribbons on radial and tangential sections, not always well demarcated from the pink or buff-coloured sapwood.
- Grain straight or slightly interlocked.
- Texture rather coarse but even; wood surface glossy.
- Growth rings vague to distinct by relatively narrow bands of denser and darker tissue or as concentric lines of terminal parenchyma; vessels visible without lens, rays not visible without lens on cross-section, and inconspicuous on the radial plane.
- Ripple marks absent.
- Growth rings marked by concentric bands of marginal parenchyma.
- Vessels evenly distributed, few, 0-7/mm2, solitary and in radial groups of 2-10 or in clusters, more or less oval, moderately large with tangential diameter of 70-310(-360) μm; perforations simple; intervessel pits alternate, 3-4 μm in diameter; vessel-ray and vessel-parenchyma pits similar to intervessel pits; helical thickenings present but not pronounced; white or light brown to dark red resin or gum present in wood; tyloses sparse or absent.
- Fibres 750-1450 μm long, usually septate, walls 3-4μm thick, with simple to minutely bordered pits mainly confined to the radial walls.
- Parenchyma in marginal, concentric bands and vasicentric to weakly aliform, in 3-8-celled strands.
- Rays 4-12/mm, uniseriate heterogeneous; biseriate rays scarce; upright cells alternating with procumbent cells, 1-28 cells in height (maximum 520 μm); lumina with red gum and usually with crystals, 1-3 per cell.
Species studied: P. pinnata.
Growth and development
Seedlings that are partly damaged can regenerate well. Height growth in the first years is rapid (3-5 m/year) when fully released but may be much less (11.6 cm in the first year). In naturally established stands the boles are usually well-formed, straight and long. Flowering periods seem to be fixed per region, with the fruiting season 2-5 months later, but is apparently not correlated with climatic seasons. Bisexual and male flowers are reported to occur on a single tree of P. pinnata, but the structurally hermaphrodite flowers are functionally female with no anther dehiscence. Both cross-fertilization and self-fertilization occur. Usually there are 3-4 times as many male as female flowers. Dispersal of the fruits is probably mostly by bats and birds.
Kasai can often be recognized from a great distance by its witches' brooms. These dense masses of leaves, twigs or sometimes inflorescences are typically abundantly hairy. They are up to 1 m in diameter, are shed as a whole and can sometimes be found in large quantities underneath the tree.
Other botanical information
The genus Pometia belongs to the tribe Nephelieae , within which it takes a rather isolated position. P. pinnata is an extremely variable species. No less than 8 forms have been recognized and given taxonomic status, but because still other and intermediate forms are encountered, this distinction is probably only useful in e.g. breeding. For reasons of completeness the 8 forms distinguished are given here:
- f. pinnata (synonym: P. coriacea Radlk., 1913);
- f. acuminata (Hook.f.) Jacobs (synonyms: P. acuminata (Hook.f.) Radlk., 1877, P. annamica Gagn., 1947);
- f. alnifolia (Blume) Jacobs (synonym: P. alnifolia (Blume) Radlk., 1877);
- f. cuspidata (Blume) Jacobs;
- f. glabra (Blume) Jacobs (synonym: P. pinnata var. javanica Koord. & Valeton, 1903);
- f. macrocarpa (Kurz) Jacobs (synonym: P. macrocarpa Kurz, 1875);
- f. repandra Jacobs;
- f. tomentosa (Blume) Jacobs (synonym: P. tomentosa (Blume) Teijsm. & Binnend., 1866).
Kasai is easy to identify; the bark often resembles that of Intsia but is distinguished by the red gum.
Kasai occurs typically in rain forest at altitudes below 500 m. Sometimes, however, it is found to 1000 m above sea-level, and occasionally even to 1700 m in some parts of northern Sumatra (Aceh). It occurs on a variety of soils, on limestone, clayey, sandy or loamy soils, mostly in dryland forest, occasionally in freshwater swamps. In western Malesia it is confined to valleys. In Papua New Guinea and the Solomon Islands it occupies a wider range of habitats and is commonly dominant in forest influenced by shifting cultivation and then prefers well-drained limestone soils. Kasai cannot tolerate a severe dry season.
Propagation and planting
Propagation is by seed. Natural regeneration from seeds has often been observed as quite abundant in disturbed or clear-cut forest areas, e.g. at Keravat (Papua New Guinea) and Jayapura and Manokwari (Irian Jaya). Regeneration counts have recorded more than 1000 young trees/ha, which might be sufficient to establish pure stands. No such pure stands are encountered, however, and commonly a mixture with other commercial species such as Dracontomelon dao (Blanco) Merr. & Rolfe is present. Artificial regeneration by means of cuttings and seeds is possible. The survival rate of six-month-old seedlings planted in the field at Manokwari (Irian Jaya) was 86%.
The seeds have no dormancy, and start to germinate 1-5 weeks after sowing or after they have fallen to the ground. On cleared land in New Guinea, kasai seedlings often soon establish, probably from seeds dropped by birds or bats. Removal of pericarp and arillode promotes seed germination, and when these are removed, germination takes place within 3 days when sown in pots in the greenhouse, with a germination rate of 85-95%.
Diseases and pests
Kasai trees often show malformations known as witches' broom, caused by a fungus or virus. Locally in Papua New Guinea a large number of kasai trees have been reported to be affected by an unidentified fungus causing white rot; the wood of affected logs is only suitable for pulping. In Peninsular Malaysia there are reports of fruits damaged by the moth Conopomorpha cramerella (Gracillaridae).
A 24 500 ha tract of forest in North Oransbari, New Guinea, had a potential yield of 30.9 m3/ha.
Genetic resources and breeding
Conservation does not seem to be a priority for the moment, but the extreme variability of P. pinnata might be diminished by local eradication through large-scale clearing of the forest.
Local varieties of P. pinnata used for fruit production have been selected and bred to obtain larger and better-tasting fruit. A race with very large arillodes has been bred in Santa Cruz (the Solomon Islands).
There is a growing awareness of the potential of kasai, and special interest in supply from New Guinea and the Solomon Islands. The potential for reforestation is good, but neither the timber quality nor bole form merit the tree being given priority in reforestation activities. Local kasai fruit production may easily be superseded by better fruit-producing tree species.
- Bolza, E. & Kloot, N.H., 1966. The mechanical properties of 81 New Guinea timbers. Technological Paper No 41. Division of Forest Products, CSIRO, Melbourne. pp. 32-35.
- Burgess, P.F., 1966. Timbers of Sabah. Sabah Forest Records No 6. Forest Department, Sabah, Sandakan. pp. 443-446.
- Fundter, J.M. & Wisse, J.H., 1977. 40 belangrijke houtsoorten uit Indonesisch Nieuw Guinea (Irian Jaya) met de anatomische en technische kenmerken [40 important timber species from Indonesian New Guinea (Irian Jaya) with their anatomical and technical characteristics]. Mededelingen Landbouwhogeschool Wageningen 77-9: 157-162.
- Jacobs, M., 1962. Pometia (Sapindaceae), a study in variability. Reinwardtia 6: 109-144.
- Keating, W.G. & Bolza, E., 1982. Characteristics, properties and uses of timbers. Vol. 1. South-East Asia, northern Australia and the Pacific. Inkata Press Proprietary Ltd., Melbourne, Sydney & London. p. 280.
- Lim, S.C., 1984. Malaysian timbers - kasai. Malaysian Forest Service Trade Leaflet No 92. Malaysian Timber Industry Board, Kuala Lumpur. 7 pp.
- Malaysian Timber Industry Board, 1982. 100 Malaysian timbers. Kuala Lumpur. pp. 52-53.
- Martawijaya, A., Kartasujana, I., Kadir, K., & Prawira, S.A., 1986. Indonesian wood atlas. Vol. 1. Forest Products Research and Development Centre, Bogor. pp. 64-68.
- van Royen, P., 1964. Manual of the forest trees of Papua and New Guinea. Part 2 - Sapindaceae. Department of Forests, Administration of Papua and New Guinea, Port Moresby. pp. 35-40.
- Yap, S.K., 1989. Sapindaceae. In: Ng, F.S.P. (Editor): Tree flora of Malaya. Vol. 4. Longman Malaysia SDN Berhad, Kuala Lumpur. pp. 434-461.
Selection of species
- N.R. de Graaf (general part, selection of species),
- J.W. Hildebrand (general part, selection of species),
- P.B. Laming (properties),
- J.M. Fundter (wood anatomy)