Anisoptera (PROSEA)

Plant Resources of South-East Asia
Introduction

Protologue: Temminck, Verh. Natuurl. Gesch. Ned. Overz. Bez., Botanie, Kruidk.: 65 (1841).

Family: Dipterocarpaceae

Chromosome number: x= probably 11; A. costata: 2n= 20, A. laevis: 2n= 22, A. scaphula: 2n= 20, 22

Trade groups

Mersawa: lightweight hardwood, e.g. Anisoptera laevis Ridley, A. marginata Korth., A. thurifera (Blanco) Blume.

Vernacular names

Mersawa

Brunei: benchaloi
Malaysia: kayu pengiran (Sabah), kelapok (Iban)
Philippines: palosapis
Burma: kaunghmu, kaban, boilam
Cambodia: phdiek, trabak, ven ven
Laos: bak
Thailand: krabak, tabak (Lampang)
Vietnam: vên vên.

Origin and geographic distribution

Anisoptera consists of 11 species and is distributed from Bangladesh eastwards towards Thailand and Vietnam and throughout Malesia to New Guinea. The majority of the species are confined to western Malesia. The genus is absent from the Lesser Sunda Islands. Holocene fossils have been discovered in north-western India.

Uses

The timber is extensively used for general light construction such as door and window frames, weatherboards, decorative panelling, ceilings, beams and scantlings, girders, rafters, packing cases, crates and boxes, vehicle bodies and furniture. Other uses are for butcher's blocks, drop siding, spools, baseball bats, venetian blinds and clothes hangers. Due to the moderate durability of the wood, it should not be used in contact with the ground. It is suitable for light to medium traffic flooring. Since the wood is resistant to marine borer attack, it is suitable for ship building, barrels and vats. It is in great demand for plywood manufacturing and can be used both as core and face veneer.

Comparatively small amounts of resin can be obtained from the trees; this is sometimes mixed with other kinds of resin and used locally for torches and caulking boats. It is not collected on a commercial scale. In some areas of Papua New Guinea the nuts of A. thurifera, which are rich in edible oils, are eaten after being cooked. The gum is used traditionally as a chewing gum.

Production and international trade

The export of sawn mersawa timber from Peninsular Malaysia in 1981 was 14 000 m³ with a value of US$ 1.6 million. The annual quantity exported was more or less stable until 1987, when it increased suddenly to 53 000 m³ with a value of US$ 7.4 million. In 1990 the largest annual export quantity of 63 000 m³, worth US$ 15.8 million, was reached; in 1992 the export was 42 000 m³, worth US$ 15.0 million. Fairly large amounts of mersawa are also exported from Borneo. For instance, the export of round logs from Sabah in 1987 was 43 000 m³ with a value of US$ 3.1 million, and in 1992 17 000 m³ of round logs and 6500 m³ of sawn timber with a total value of US$ 3.5 million. Recently small amounts of mersawa ("palosapis") have been exported from the Philippines; in 1980 the export value was US$ 196 000 but it fell to US$ 19 000 in 1988 and was only US$ 2500 in 1989. Production and export figures are not available from Papua New Guinea and Sarawak, or from Indonesia. Undoubtedly, mersawa is important for plywood production in Indonesia. Japan imports fairly large amounts of mersawa, particularly from Papua New Guinea, Sabah and Sarawak.

Mersawa has some importance in Burma, Indo-China and Thailand. The annual production at the beginning of the 1980s was about 1000 m³ in Burma, 25 000 m³ in Cambodia, and 10 000 m³ in Thailand.

Mersawa is sometimes traded in mixed consignments with white and yellow meranti (Shorea spp.).

Properties

Mersawa is a light to moderately heavy hardwood. The sapwood is very pale yellow when fresh, becoming darker on exposure and often not clearly demarcated from the light to dark yellow heartwood which sometimes has a rose tinge and which also darkens to a straw brown on exposure. The density is (460-)510-740(-895) kg/m³ at 15% moisture content. The grain of the wood is straight to interlocked or sometimes slightly spiral, texture moderately coarse but even.

Tests of mersawa wood in green condition in Indonesia, Malaysia, the Philippines and Papua New Guinea showed the following mechanical properties: modulus of rupture 49-76 N/mm², modulus of elasticity 9200-12 800 N/mm², compression parallel to grain 25-33 N/mm², compression perpendicular to grain 4.5-6 N/mm², shear 5.5-7.5 N/mm², cleavage 50-65 N/mm radial and 54-69 N/mm tangential, Janka side hardness 2185-4180 N and Janka end hardness 2740-3600 N.

Tests in Indonesia at 15% moisture content showed the following figures: modulus of rupture 67-81 N/mm², modulus of elasticity 9600-12 150 N/mm², compression parallel to grain 36-45 N/mm², shear 6-8 N/mm², cleavage 56-66 N/mm radial and 61-73 N/mm tangential, Janka side hardness 2215-3520 N and Janka end hardness 2450-3310 N.

The rates of shrinkage are moderate, from green to 15% moisture content 1.4% radial and 3.2-3.8% tangential, from green to oven dry the shrinkage may be as much as 3.8% radial and 11% tangential. Mersawa air dries very slowly with slight seasoning defects such as cupping and bowing. Boards of 25 mm and 40 mm thick take respectively 7.5 months and 9 months to air dry. In Malaysia kiln schedule E is recommended. Kiln drying is also slow but without degrade, although the core of logs of old trees tends to retain a high moisture content. After satisfactory drying, the wood is fairly stable in service.

Mersawa is difficult to rip, to cross cut and to plane because of the presence of silica. Stellite-tipped saws are necessary. The planed surface is smooth when sharp tools are used, and boring and turning is easy, giving smooth surfaces (although sometimes rough after boring). Mersawa is easy to nail and screw, and holds nails and screws well.

It is suitable to be peeled for veneer of good quality, although the veneer dries slowly and with slight buckling. The gluing properties are good and good-quality plywood can be made. Experimental particle boards made in Malaysia with 8% resin and 1% wax and with a density of 634 kg/m³ had properties exceeding those stipulated in the British standards. Hardboards made from wood of A. scaphula in Thailand had good properties, both by wet- and dry-processes (satisfying the specifications stipulated in the Japanese standard).

Mersawa is classified as moderately durable under exposed conditions. Untreated stakes of A. marginata (600 mm × 50 mm × 50 mm) lasted 5 years in graveyard tests in Malaysia. Mersawa is very susceptible to fungal attack; blue stain infection of the sapwood occurs easily. It is moderately susceptible to attack by Lyctus beetles and termites. However, because of the fairly high silica content, it is rather resistant to marine borers. Mersawa is difficult to treat with preservatives. Absorption of creosote is less than 32 kg/m³ using the open tank process.

Description

Medium-sized to very large trees up to 65 m tall; bole straight, branchless for up to 30 m, and up to 150(-200) cm in diameter, often with prominent, thick, rounded, tall and straight buttresses; outer bark highly variable between immature and mature trees, up to 2 cm thick, containing resin, greyish or yellowish, dotted with warty lenticels, shallowly and irregularly fissured, ridges flat and flaking, inner bark laminated with alternate layers of light and dark yellow; crown comparatively small, with a few large and twisted branches; twigs ribbed; young parts at first densely lepidote with emarginate peltate (scale-like) hairs.
Leaves alternate, simple, entire, oblong to ovate, base usually obtuse, apex shortly acuminate, lower surface persistently covered with peltate hairs; secondary veins curved and anastomosing at the apex; petiole distinctly geniculate; stipules relatively large, narrow and fugaceous.
Inflorescence a long, lax, pendant, densely tomentose panicle; bracteoles small, linear, caducous.
Flowers bisexual, regular, 5-merous, distinctly pedicellate in bud; calyx imbricate or rarely valvate, 2 outer lobes obtuse and slightly more thickened than the 3 inner acute ones, united at base in an indistinct tube; corolla with oblong-linear petals, which are shed separately; stamens 15-65, in 3 verticils or irregularly placed, the outer somewhat shorter than the inner, glabrous, filaments rather short, slender, filiform, connate at base, anthers latrorse, the inner 2 pollen sacs shorter than the outer 2, with a long or short appendage; ovary 3-locular, semi-inferior, with enlarged stylebase forming a distinct stylopodium, style long or short, obscurely trifid, stigma minute.
Fruit a globose or subglobose nut, the fruit calyx with an ellipsoid tube almost entirely enclosing the nut and adnate to it, with 2 long, narrowly spatulate, obtuse, untwisted, 3-veined lobes and 3 acuminate short lobes.
Seed lacking endosperm.
Seedling with epigeal germination; cotyledons unequal, chlorophyllous; the first leaves paired, with interpetiolar stipules, or in a whorl of 4 without stipules, subsequent leaves arranged spirally.

Wood anatomy

Macroscopic characters

Heartwood light to dark yellow, usually with a characteristic rose tinge or with streaks when fresh, darkening on exposure, often not clearly demarcated from the sapwood (very pale yellow when fresh, becoming darker on exposure).
Grain straight, interlocked or sometimes spiral.
Texture moderately coarse but even; prominent ribbon figure sometimes present.
Freshly sawn wood from Papua New Guinea sometimes with mild resinous odour.
Growth rings indistinct; vessels moderately large, visible to the naked eye, vessel lines conspicuous on longitudinal surfaces, tyloses sparse to abundant; parenchyma diffuse; rays of two sizes, finer rays not visible without lens, larger rays not conspicuous on longitudinal surfaces; ripple marks absent.
Axial intercellular canals as large as vessels (A. laevis) to less than half the vessel diameter (A. scaphula), mostly scattered, but sometimes in long tangential series (especially in A. costata), very scarce in A. laevis and A. scaphula, and numerous in A. costata and A. marginata.

Microscopic characters

Growth rings indistinct or absent.
Vessels diffuse, 5-8(-12)/mm², predominantly solitary (over 95%) with a few pairs, uniformly distributed, generally oval, average tangential diameter 145-250μm; perforation plates simple; intervessel pits alternate, vestured, with a pit border diameter of 6-8μm; vessel-ray pits with reduced borders to almost simple, rounded, c. 20μm; tyloses present.
Vasicentric tracheids present as well as cells grading from vasicentric tracheids to fibres in the immediate proximity of the vessels.
Fibres 1.0-1.2 mm long, non-septate, thick-walled, with conspicuously bordered pits mainly confined to the radial walls.
Parenchyma paratracheal, occasionally aliform; apotracheal parenchyma diffuse or short aggregates between the rays, strand length 4-6 cells.
Rays of 2 sizes, (3-)4-7(-9)/mm, mostly multiseriate 4-10(-11) cells wide, up to 2 mm high, heterocellular with 1-3 rows of square to upright marginal cells (Kribs type heterogeneous III and II), uniseriates few, short, sheath cells prominent.
Horizontal intercellular canals absent; axial gum canals diffusely scattered, sometimes in more or less tangential series, commonly occluded with chalky white deposits, diameter of canals large in A. laevis (c. 160μm), smaller in other species (60-120μm).
Silica bodies present, abundant in some species, mainly in the marginal ray cells, also in parenchyma cells in some species.

Species studied: A. aurea, A. costata, A. curtisii, A. grossivenia, A. laevis, A. marginata, A. scaphula, A. thurifera.

The axial gum canals enable mersawa to be distinguished from non-dipterocarps. The larger pores, the lower density and distinctive colour of the wood separate mersawa from keruing (Dipterocarpus spp.), resak (Vatica spp.) and upun (Upuna borneensis Sym.); the distribution of axial canals helps to distinguish it from Hopea spp.

Growth and development

Germination of A. thurifera seeds has been studied in Papua New Guinea. Seeds often germinate while the fruit is still on the tree (viviparous), the radicle breaking through the upper section of the globose nut. Usually seedlings will not survive in the shade of a dense subcanopy; they require high light intensity and occur naturally along forest margins and in logged forest, actively colonizing old logging tracks. Under these conditions, initial growth rates are high. However, seedlings of A. thurifera are also reported to survive in the forest under heavy shade.

Growth is fairly rapid; trees of A. thurifera may already reach a bole diameter of 30-45 cm after 12 years. At this age the larger individuals are sexually mature and the smaller trees are suppressed and start to die. Trees of A. scaphula may reach a bole diameter of 65 cm in 40 years. For A. laevis the growth rate is less rapid: a maximum diameter of 45 cm can be reached in 40 years.

The trees need mycorrhizal infection for optimal growth. A. thurifera in Papua New Guinea may be infected by a variety of ectomycorrhizae which are also found on Castanopsis spp. and Lithocarpus spp.

In stands studied in Papua New Guinea, A. thurifera usually flowered and fruited annually. If conditions are unfavourable, flowering may not occur. Although the fruit is winged, the dispersal of nuts is restricted; over 90% of the seedlings occur under the parent tree.

The resin of A. thurifera is collected by bees to build their nests.

Other botanical information

The genus Anisoptera is divided into 2 sections: section Anisoptera (8 species in Malesia) and section Glabrae Heim (2 species in Malesia), based on the form of the flower buds, number of stamens, form of the stylopodium, length of the style and form of the stigma. The genus Anisoptera is included in the tribe Dipterocarpeae, together with Dipterocarpus, Upuna, Cotylelobium and Vatica. It differs mainly from the latter 3 genera by the calyx which is united into a tube at base and encloses at least half of the nut. Anisoptera differs mainly from Dipterocarpus by the nut being adnate to the calyx tube (in Dipterocarpus the nut is free), the peltate hairs on innovations and leaf beneath (absent in Dipterocarpus) and the prominent looped intramarginal vein (absent in Dipterocarpus).

Ecology

Species of mersawa are canopy trees or rarely emergents generally occurring in primary but sometimes secondary evergreen or semi-evergreen rain forest. They usually occur scattered but several species (e.g. A. thurifera) grow markedly gregariously. Mersawa usually occurs on well-drained soils but also in peat swamps and in kerangas (heath forest) on podzols. Preferred sites are low hills and ridges at altitudes of up to 1200 m.

Propagation and planting

Seeds rapidly lose their viability; after 2-3 weeks the germination rate is often already almost zero. Tests on fresh seeds of A. costata, collected from trees and the ground soon after falling, showed a germination rate of 80-90%. Seeds can be stored for very short periods only. The best temperature for storage of A. thurifera seeds is 18°C. The moisture content should be reduced to 20-25% by air drying, and the seeds should be packed in polyethylene bags. Viability is significantly reduced when the moisture content of the seeds falls below 14%.

Vegetative propagation can be practised successfully. Trials on air layering branches of A. thurifera in the Philippines showed some success: 25% of the branches developed roots. Grafting had 10% success. In Malaysia, A. scaphula is propagated by cuttings. Short cuttings, consisting of one node with its leaf and axillary bud and part of the internode below, can be used, or 12-15 cm long cuttings prepared from leader shoots and branches of vigorously growing young plants (about 2 years old) raised from seeds in the greenhouse. When the cuttings are treated with indole butyric acid, they produce green buds in a period of 16-25 days and have a rooting rate of 80%. The shoots are 20-25 cm tall after one year. The cuttings are placed in beds of washed coarse sand, and should be kept moist, e.g. by a mist-spraying mechanism. The beds should be shaded, for instance with green plastic net, so that the relative light intensity is maintained below 10%.

Both in vegetative and seed propagation a mycorrhiza has to be provided to realize optimal growth.

Silviculture and management

A. thurifera is known to invade disturbed areas and can be an agressive invader following logging in the Philippines and Papua New Guinea. It readily reinvades cultivated land. The trees are used in Papua New Guinea to fill up gaps in selectively logged tropical rain forest. Natural regeneration of other species of mersawa is recorded as sparse, and strip planting is practised in Indonesia to maintain a fair share of mersawa in the forest after logging.

Harvesting

Trees are harvested according to the selective felling systems as practised in various countries. In Indonesia the diameter limit is 50 cm. Logs should be removed quickly from logging areas since they are susceptible to blue stain (particularly the sapwood) and sometimes also to pinhole borers (ambrosia beetles). Mersawa logs usually sink in water; this is due to the high water content of green logs. Transport must be over land. The core of old trees is sometimes hollow.

To tap the resin, the bark is scraped off and V-shaped incisions are made in the sapwood after which sulphuric acid is sprayed into the streaks. Resin can be collected weekly, and after each collection the trees are rechipped and sulphuric acid reapplied. Trees with a bole diameter of at least 60 cm yield more resin than smaller trees.

Yield

In Indonesia the average standing stock of mersawa timber is 2.1 m³/ha for trees over 50 cm in diameter. Locally this figure may be higher, e.g. in the Moluccas where a value of 10 m³/ha was obtained.

Genetic resources

Some species are gregarious and widespread (e.g. A. costata, A. thurifera) and seem not to be at risk of genetic erosion. Other species are scattered and not common (e.g. A. marginata, A. megistocarpa) and are more vulnerable to genetic erosion.

Prospects

Mersawa seems to be promising for enrichment planting in selectively logged forest and for reforestation of logged-over areas. The timber can be used for various purposes, and the trees are often rapid growers. A. thurifera in particular should receive more attention in research.

Literature

America, W.M., 1974. Wood of the "palosapis" group. Forpride Digest 3: 67-68.
Ashton, P.S., 1982. Dipterocarpaceae. In: van Steenis, C.G.G.J. (Editor): Flora Malesiana. Ser. 1, Vol. 9. Martinus Nijhoff/Dr. W. Junk Publishers, the Hague, Boston, London. pp. 327-337.
Johns, R.J., 1987. The natural regeneration of Anisoptera and Hopea in Papua New Guinea. In: Kostermans, A.J.G.H. (Editor): Proceedings of the third round table conference on dipterocarps, Samarinda. UNESCO-ROSTSEA, Jakarta & SEAMEO-BIOTROP, Bogor. pp. 213-233.
Lopez, D.T., 1981. Malaysian timbers - mersawa. Malaysian Forest Service Trade Leaflet No 56. Malaysian Timber Industry Board, Kuala Lumpur. 8 pp.
Martawijaya, A., Kartasujana, I., Kadir, K. & Prawira, S.A., 1986. Indonesian wood atlas. Vol. 1. Forest Products Research and Development Centre, Bogor. pp. 93-97.
Masano, 1988. Perkecambahan benih Anisoptera costata Korth. [Seed germination of Anisoptera costata Korth.]. Buletin Penelitian Hutan No 498: 11-21.
Momose, Y., 1978. Vegetative propagation of Malaysian trees. Malaysian Forester 41: 219-223.
Srivastava, P.B.L. & Penguang Manggil, 1981. Vegetative propagation of some dipterocarps by cuttings. Malaysian Forester 44: 301-313.
Tucay, J.L.A., 1985. Prolonging seed viability of palosapis (Anisoptera thurifera (Blanco) Blume) in storage. Thesis, University of the Philippines, Los Baños, College, Laguna. 98 pp.
Zabala, N.Q., 1986. Vegetative propagation of some dipterocarp species. Philippine Lumberman 32: 13-16.

Selection of species

Authors

R.J. Johns (general part),
W.C. Wong (properties),
J. Ilic (wood anatomy),
M.H.A. Hoffman (selection of species)