Pentace (PROSEA)

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Plant Resources of South-East Asia Introduction

List of species

Pentace Hassk.

Protologue: Hort. bogor. descr.: 110 (1858).

Family: Tiliaceae

Chromosome number: x= unknown

Trade groups

Melunak: lightweight to medium-weight hardwood, e.g. Pentace burmanica Kurz, P. laxiflora Merr., P. polyantha Hassk., P. triptera Masters.

Melunak is sometimes traded in mixed consignments with surian batu ( Chukrasia tabularis A.H.L. Juss.), red meranti ( Shorea spp.) or other reddish woods.

Vernacular names

• Melunak: Burma mahogany (En). Brunei: kedang pinit
• Indonesia: kayu pinang
• Malaysia: takalis (Sabah), bary baran (Sarawak). Burma (Myanmar): thitka, thit-kashit, thit-sho
• Cambodia: tassiet
• Laos: sisièt
• Thailand: sisiat, sisiat-pluak (central, peninsular), thongsuk (Nakhon Si Thammarat).

Origin and geographic distribution

Pentace consists of 27 species. They are distributed in Burma (Myanmar), Indo-China, Thailand, Peninsular Malaysia, Sumatra, western Java, Borneo, Sulawesi and the southern Philippines. The main centres of diversity are found in Peninsular Malaysia (16 species) and Borneo (12 species).

Uses

The wood is used extensively for light construction such as weatherboards, decorative panelling, ceilings, beams, scantlings, furniture of good quality, and it is also highly valued for cabinet work. Other applications are for musical instruments, mathematical instruments, boat building, mouldings, flooring, handicraft, paddles and gunstocks.

The bark is used locally for house walls, or chewed together with betel nut ( Areca catechu L.).

Production and international trade

Melunak is traded in fairly large amounts from Borneo. In 1987, the export of melunak round logs from Sabah was 61 000 m³with a value of US$ 3.8 million, and in 1992 it was 38 000 m³(26% as sawn timber, 74% as logs) with a total value of US$ 3.7 million. Elsewhere, the amounts traded are only small and no trade figures are available; the wood is mainly used domestically, e.g. in Thailand. Small amounts are imported into Japan, mainly from Sabah and Sarawak, often in mixed consignments with red meranti.

Properties

Melunak is a lightweight to medium-weight, sometimes heavy hardwood. The heartwood is golden brown, reddish-brown or deep red-brown, generally darkening on exposure. The sapwood is paler and more yellowish, but often not clearly demarcated from the heartwood. The density varies greatly among species, (320-)500-750(-960) kg/m³at 15% moisture content. The grain is usually shallowly to deeply interlocked, texture moderately fine and even; planed surfaces are lustrous and the wood has no distinctive odour or taste, radial surfaces show narrow, regular stripes.

At 16% moisture content, wood of P. triptera has the following mechanical properties (based on a test in Peninsular Malaysia): the modulus of rupture 85 N/mm², modulus of elasticity 12 000 N/mm², compression parallel to grain 44 N/mm², compression perpendicular to grain 4.5 N/mm², shear 11 N/mm², Janka side hardness 4100 N and Janka end hardness 5220 N.

The rates of shrinkage are fairly low to moderate: from green to 15% moisture content 1.4% radial and 2.5% tangential and from green to oven dry 3.5-4.2% radial and 6.5-7.6% tangential. The timber air dries rather slowly and with slight defects such as bowing, twisting and checking (slightly more degrade than in red meranti). Boards 15 mm thick take about 3.5 months to air dry, and boards 40 mm thick take about 5 months. Kiln drying is satisfactory.

The working properties vary from easy to moderately difficult, generally because of differences in density of the wood among species; the lighter wood is easier to work than the heavier wood. Generally the wood is satisfactory to work with hand and machine tools, although the interlocked grain can cause problems with tearing when radial surfaces are planed. Melunak bores, turns, nails, glues and finishes well, but tends to splinter rather easily. There is little information on slicing or rotary peeling, but a test on one billet of P. triptera in Peninsular Malaysia showed that 1.6 mm thick veneer can easily be obtained in continuous length without any heat treatment; the veneer was attractive and dried well without much degrade. Melunak may be suitable for decorative plywood used for high-class furniture and cabinet work, but it has also been reported that melunak is mainly used as core material for plywood. Quartered sliced veneer can be particularly decorative.

Reports on heartwood durability are variable; the wood of some species is rated as non-durable and that of others as durable, but most wood is moderately durable. In graveyard tests in Malaysia, the average service life of test stakes in contact with the ground was 2.1 years. The heartwood isdifficult to treat with preservatives; in a test in Malaysia using the open tank process and an equal mixture of creosote and diesel fuel, an absorption of only 17 kg/m³was achieved. The sapwood is more permeable.

The chemical contents of wood of P. floribunda and P. triptera were tested in Malaysia. The wood contains 70-73% holocellulose, 46-47%α-cellulose, 28% lignin, 11-12% pentosan and 0.4-0.8% ash. The solubility of P. floribunda wood is 3.0% in alcohol-benzene, 5.4% in hot water and 11.5% in a 1% NaOH solution. The solubility of P. triptera wood is 0.6% in alcohol-benzene, 1.8% in hot water and 8.7% in a 1% NaOH solution.

Description

Small to large trees up to 60 m tall; bole straight, up to 125 cm in diameter, with short to tall buttresses; bark surface shallowly fissured to scaly and flaky, grey-brown to dark brown, inner bark laminated, pink to red. Newly formed shoots, inflorescences and lower leaf surfaces covered with stellate hairs or scales. Leaves arranged spirally, simple, elliptical to ovate or slightly obovate, sometimes slightly 3-lobed, margin entire or dentate, base obtuse to cordate, palmately veined with 3(-7) main veins which are depressed above, tertiary venation usually scalariform; petiole slender, swollen at both ends; stipules early caducous. Inflorescence terminal or axillary, lax. Flowers bisexual, regular, 5-merous; sepals united in a shallow tube, densely scaly outside, with triangular lobes; petals free, spatulate, white, glabrous; stamens many, free or in 5 indistinct bundles with the filaments united at base, inner row staminodial; ovary superior, 3-10-ribbed, densely stellate-scaly, 3-10-celled, with 2 ovules in each cell, style 1, apically sometimes divided into 3-5 arms, stigma truncate. Fruit a non-dehiscent samara with 3-10 wings, 1-seeded, covered with stellate hairs, scales and/or bristles. Seed albuminous; cotyledons thick, oblong.

Wood anatomy

• Macroscopic characters:

Heartwood golden brown, reddish-brown or deep red-brown, darkening on exposure, not clearly distinct from the yellowish sapwood. Grain usually shallowly interlocked. Texture moderately fine and even; quartered surfaces with narrow and regular stripe figure. Growth rings distinct or indistinct, delimited by darker bands of fibres or marginal bands of parenchyma; vessels barely visible to the naked eye, tyloses occasional to infrequent but mostly absent; parenchyma difficult to see with hand lens, in fine narrow marginal bands or finely diffuse or diffuse-in-aggregates; rays not visible with the naked eye; ripple marks distinct on all surfaces.

• Microscopic characters:

Growth rings distinct or indistinct, sometimes demarcated by uniseriate to biseriate bands of axial parenchyma. Vessels diffuse, mostly 9-20/mm², solitary and in short radial multiples (sometimes in radial multiples of 5-8 and in tangential pairs or clusters of 3-7), (100-)120-200(-250)μm in tangential diameter; perforation plates simple; intervessel pits alternate, non-vestured, circular or oval, 2-4μm; vessel-ray pits simple or with much reduced borders, enlarged, horizontally to vertically elongated or round; thin-walled tyloses occasional to infrequent but mostly absent. Fibres 1.4-1.8 mm long, non-septate, thin-walled to thick-walled, with simple to minutely bordered pits. Axial parenchyma abundant, predominantly diffuse or diffuse-in-aggregates, paratracheal parenchyma generally narrowly vasicentric, banded parenchyma infrequent and faint but occasionally in marginal bands (irregularly zonate), in 8-celled strands. Rays 6-9/mm, 200-500μm high (storied, sometimes rays span two tiers doubling the ray height), homocellular to heterocellular with one row of upright and/or square marginal cells, 2-4(-5) cells wide. Crystals and silica bodies absent. Generally all elements storied, rays in 2-3 tiers/mm.

Species studied: P. burmanica , P. curtisii , P. laxiflora , P. triptera .

Growth and development

A 33-year-old P. triptera tree in the arboretum of the Forest Research Institute Malaysia was 24 m tall with a clear bole of 7 m and a diameter of 36 cm, i.e. a mean annual diameter increment of 1.1 cm. The mean annual diameter increment of P. burmanica is reported as 1.3-1.7 cm and that of Pentace sp. from Sabah 0.5-1.0 cm.

The flowering to fruiting period for a single P. strychnoidea tree under partial shade was observed as 3-5 months; the tree flowered only once in 6 years of observation. Fruiting of P. triptera in Peninsular Malaysia is more frequent than that of dipterocarps (once in 2-5 years). The fruits are dispersed by wind.

Other botanical information

Pentace is closely related to Brownlowia . Sterile material is difficult to ascribe to either of the genera. The two genera differ in fruit characters, Pentace having winged, wind-dispersed fruits and Brownlowia having wingless water-dispersed fruits.

Pentace and Pentacme (a synonym of Shorea ) are sometimes confused with each other.

Ecology

Melunak is usually fairly common but scattered in primary evergreen lowland or hill rain forest in well-drained locations such as hill slopes, ridges, or near small streams, up to 1000 m altitude. Melunak trees are generally shade-loving trees persisting under heavy shade for years. P. rigida , found in Sarawak, is probably a light-demanding species, however. Occasionally, menulak is found as a pioneer in fire breaks. Some species prefer limestone, sandstone or podzolic soils, whereas others are also found in seasonal swamps.

Propagation and planting

For Peninsular Malaysia the following data are available on the propagation of melunak (mainly P. triptera ). Seeds lose their viability in less than one week and germination starts in a few days. Fresh, ripe fruits have red to reddish-brown wings; pale-coloured wings indicate immaturity. Fruits should be sown with one wing vertical, the seed just in the soil and the other two wings buried.

Seedlings a few months old have been planted very successfully. Small trials where wildlings were planted under the shade of secondary vegetation showed 68% and 54% success, respectively, in two different blocks. Natural regeneration is generally good, and dense carpets of seedlings can be found under mother trees, presumably because of inefficient seed dispersal. Wildlings can easily be collected from these spots. No plantations of Pentace spp. have been established.

Silviculture and management

Sudden exposure to more light, as in large openings, does not harm established seedlings. Fairly large stumps of P. rigida coppice freely. In Peninsular Malaysia, P. triptera is among the specially desired species in regenerating forest, and 5-15 years after logging it should be freed from competition if it has leaders in the canopy.

Harvesting

Logs are generally free from defects. The amount of bark peeled from living trees for chewing should not exceed two stripes of 10 cm wide for a tree of about 50 cm diameter.

Yield

The standing stock of melunak in forests in Burma (Myanmar) is estimated as about 25 m³of wood per ha. The standing stock of melunak in various forests in East Kalimantan varies between 8.6 and 53.3 m³/ha.

Handling after harvest

The ends of logs should be treated with tar. Bark should be kept dry. It is often traded on markets together with the bark of Lithocarpus , Quercus and Shorea spp.

Genetic resources

Melunak trees do not seem to be at immediate risk of genetic erosion, except perhaps for some rare species. Logging of melunak trees on a larger scale is only practised locally in Borneo. == Prospects ==

Melunak may be promising for enrichment planting in selectively logged forest. The wood can be used for various purposes and the trees are often fairly rapid growers. However, more research is needed on propagation and silviculture.

Literature

• All Nippon Checkers Corporation, 1989. Illustrated commercial foreign woods in Japan. Tokyo. p. 139.
• Barnard, R.C., 1956. A manual of Malayan silviculture for inland lowland forests. Research Pamphlet No 14. Forest Research Institute, Kepong, Selangor. 199 pp.
• Browne, F.G., 1955. Forest trees of Sarawak and Brunei and their products. Government Printing Office, Kuching. pp. 345-346.
• Ho, K.S., 1983. Malaysian timbers - melunak. Malaysian Forest Service Trade Leaflet No 80. Malaysian Timber Industry Board, Kuala Lumpur. 6 pp.
• Kochummen, K.M., 1983. Tiliaceae. In: Whitmore, T.C. (Editor): Tree flora of Malaya. A manual for foresters. 2nd edition. Forest Research Institute Malaysia. Vol. 2. Longman Malaysia SDN. Berhad, Kuala Lumpur. pp. 392-412.
• Kostermans, A.J.G.H., 1964. A monograph on the genus Pentace Hassk. (Tiliaceae). Pengumuman Lembaga Penelitian Hutan No 87. 78 pp.
• Lee, Y.H. & Chu, Y.P., 1965. The strength properties of Malayan timbers. Malayan Forester 28(4): 307-319.
• Malaysian Timber Industry Board, 1986. 100 Malaysian timbers. Kuala Lumpur. pp. 158-159.
• Phengklai, C., 1986. Study in Thai flora, Tiliaceae. Thai Forest Bulletin, Botany 16: 71-75.
• Research Institute of Wood Industry, 1988. Identification, properties and uses of some Southeast Asian woods. Chinese Academy of Forestry, Wan Shou Shan, Beijing & International Tropical Timber Organization, Yokohama. p. 192.