Heritiera (PROSEA)

Plant Resources of South-East Asia
Introduction

List of species

Heritiera Aiton

Protologue: Hort. kew. 3: 546 (1789).

Family: Sterculiaceae

Chromosome number: x= unknown; H. littoralis: 2n= 20, 28, 38

Trade groups

Mengkulang: medium-heavy hardwood, e.g. Heritiera javanica (Blume) Kosterm., H. simplicifolia (Masters) Kosterm.

Dungun: heavy hardwood, e.g. H. littoralis Aiton, H. sylvatica S. Vidal.

Vernacular names

Mengkulang:

teralin (Fr).
Brunei: kembang
Indonesia: palapi, teraling
Malaysia: kembang (Peninsular, Sabah)
Philippines: lumbayau
Burma: kanazo
Laos: hao
Thailand: chumpraek (Trat).

Dungun

Indonesia: dungon
Philippines: dungon, dungon late
Burma: kanazo, pinle-kanazo
Thailand: ngonkai-thale (central, Surat Thani), duhun (Trang)
Vietnam: cây cui.

Origin and geographic distribution

Heritiera consists of about 35 species and is distributed over a large area comprising tropical Africa (2 species), southern Asia from India to New Guinea (the majority of the species), Micronesia (1 species), and tropical Australia (3 species). About 20 species occur in Malesia. H. littoralis is the most widespread species, covering almost the entire area of the genus.

Uses

Mengkulang is a very good general-purpose timber. It is not very durable, but is suitable for interior construction, flooring, furniture, ship masts and other ship constructions above the waterline. For the export market mengkulang is recommended for joinery, flooring and other purposes, as an alternative to red meranti (from Shorea spp.), niangon (from the African Heritiera utilis (Sprague) Sprague) and African mahogany (from the genus Khaya). Mengkulang is suitable for flooring subject to medium or light traffic, and also for purlins, ceiling joists, window frames, and even foundation piling (but must then be treated with preservative). It is particularly suited for staircase construction. It makes high quality veneer for core and outer layers of plywood. The wood can be used to make strong and stable particle board.

Dungun wood is of good quality, but it is not used so commonly because of the often twisted and stunted form and low branching of the bole; moreover, the timber is difficult to work. It is particularly used for rice pounders and other domestic articles, but sometimes also for piling, bridges and ship building. In the Philippines it is recommended for steamed bentwork and when strength and durability are required. Dungun was formerly valued for bulletproof shields because of its toughness.

H. littoralis has several other uses, particularly for tanning and in traditional medicine. The wood is said to be suitable for making paper.

Production and international trade

Mengkulang timber is locally commercially important, particularly in Malaysia. The export of sawn mengkulang timber from Peninsular Malaysia decreased from 1981 (44 000 m³ with a value of US$ 7 million) to 1984 (17 600 m³ with a value of US$ 2.9 million). From then on there was an increase to 1989 and 1990 (with an export volume of 39 700 m³and value of US$ 11.5 million, and 31 500 m³ and value of US$ 9.9 million, respectively). In 1992 the export was 23 000 m³ with a value of US$ 7.5 million. Mengkulang is also exported from Sarawak and Sabah, particularly to Japan. The export of round logs from Sabah was 15 000 m³ (worth US$ 1.3 million) in 1987, and the 1992 export was 6000 m³ of logs and 9000 m³ of sawn timber with a total value of US$ 3.5 million.

In other countries mengkulang is not generally available in commercially important quantities for shipment as a separate timber. It is often traded in combination with dark red lauan from the Philippines and dark red meranti from Indonesia (both from Shorea spp.). Mengkulang is much exported from the Riau Archipelago to Singapore. In Papua New Guinea, the timber is ranked in MEP (Minimum Export Price) group 4, and fetched a minumum export price for saw logs of US$ 43/m³ in 1992.

Dungun is of less commercial value and only locally important, e.g. in the Philippines.

Properties

Mengkulang is a medium-weight and moderately hard wood. The heartwood is reddish-brown to dark brown, occasionally pinkish-brown, the sapwood pale yellow-brown to reddish. The density is (520-)640-820(-990) kg/m³ at 15% moisture content. The grain is straight to shallowly interlocked, texture coarse and fairly even.

At 15% moisture content, the modulus of rupture is 70-100 N/mm², modulus of elasticity (7500-)11 000-16 000 N/mm², compression parallel to grain 50-60(-72) N/mm², compression perpendicular to grain 4-6 N/mm², shear 7-12(-16) N/mm², cleavage 52 N/mm radial and 48 N/mm tangential, Janka side hardness 4000-4500(-5900) N and Janka end hardness 6430 N.

The rates of shrinkage of mengkulang are moderate to fairly high: from green to 15% moisture content 1.3-1.7% radial, and 3.0-3.8% tangential, from green to 12% moisture content up to 3% radial and 7% tangential. Mengkulang seasons rapidly, but it has a slight tendency to warp and to exhibit surface checking. Straining is recommended to reduce warping. It takes about 3 months to dry 4 cm thick boards to air-dry condition. Mild kiln schedules are required in drying. A temperature of 57-77°C and a corresponding relative humidity of 80% to 40% are recommended. In Malaysia kiln schedule D is considered suitable. Form stability is good when dry.

Mengkulang is somewhat difficult to work due to the high silica content, which is generally less than 0.5%. Blunting effects on tools are severe to moderately severe when sawing the timber. It is easy to polish. Care is needed when planing quarter-sawn timber in order to avoid the grain picking up, but a 20° cutting angle will produce a smooth finish. Mengkulang is moderately easy to turn and chisel. The nail-holding capacity is fairly good, but pre-boring is advised. Gluing gives no problems. Finishing with the usual treatments gives good results when the grain is properly filled. The wood is suitable for plywood. It can be peeled satisfactorily. Good veneer can be made at a peeling angle of 92° without pretreatment. The fibre is used in hardboard and superhardboard with good results.

Mengkulang is rated as non-durable; stake tests show an average service life in contact with the ground of only 2-2.5 years under tropical conditions, and 5-10 years under temperate conditions. It is rated as durable for interior work in the tropics and under dry conditions. It is prone to termite and marine borer attack, but is not particularly susceptible to powder-post beetle attack. The resistance to wood-rotting fungi varies greatly, even within one species. Mengkulang is moderately easy to treat with preservatives. Applying an open tank treatment using a creosote-diesel mixture, an average absorption of 112 kg/m³ was obtained in Malaysia.

Wood of H. javanica contains 50% cellulose, 17% lignin, 12.5% pentosan, 0.8% ash and 0.4% silica. The solubility is 4.6% in alcohol-benzene, 0.8% in cold water, 3.3% in hot water and 14.6% in a 1% NaOH solution. The energy value is about 18 800 kJ/kg.

Dungun is a heavier wood, with a density of 830-1040 kg/m³at 15% moisture content. It is hard and strong; at 12% moisture content the modulus of rupture is 132 N/mm², modulus of elasticity 18 000 N/mm², compression parallel to grain 72 N/mm², shear 14 N/mm², cleavage 62 N/mm radial and Janka side hardness 7600 N.

Dungun is a timber with high shrinkage: from green to 15% moisture content about 2% radial, and about 4.5% tangential. It is more difficult to season than mengkulang, and subject to considerable end splitting and surface checking. Dungun contains rather large amounts of silica which rapidly blunt edged tools. It turns fairly well and takes a good finish.

Dungun is moderately durable when exposed to the weather or in contact with the ground; a life of 3 years in contact with the ground under tropical conditions is probably as much as can be expected. The wood is not susceptible to powder-post beetles, and is reported to be resistant to marine borers, but not always to termites. Dungun is probably difficult to impregnate with preservative because gum-like deposits are present.

The bark of H. littoralis contains 12-15% tannin on dry weight basis. The ichthyotoxic activity of the roots of H. littoralis is due to the presence of heritol, heritianin and heritonin. These compounds have potential as natural pesticides as well.

Description

Medium-sized to large monoecious trees, up to 50 m tall, with usually tall and straight bole (but often stunted and low-branched in H. littoralis), branchless up to 20 m, and up to 100(-135) cm in diameter; trunk with well-developed, but usually thin, buttresses; bark greyish to reddish-brown outside, shallowly fissured and scaly or spotted, inner bark generally pink to red, laminated; twigs usually slender and terete, usually with prominently raised leaf scars, often with clustered or stellate hairs, and scaly.
Leaves alternate, principally compound with palmately arranged leaflets, but also unifoliolate, and then seemingly simple; petiole swollen at both ends; leaflets entire, usually finely scaly beneath.
Inflorescence axillary, paniculate, pubescent at the base, scaly or stellate-hairy towards tip.
Flowers unisexual, very small, with 4-5(-6)-lobed calyx and lacking corolla; male flowers much more numerous than female ones, having an androgynophore bearing 8-10 sessile anthers and with or without minute sterile ovaries; female flowers slightly larger than male ones, having 4-5(-6) sessile small ovaries with short styles, alternating with small groups of sterile anthers.
Fruit an ellipsoid to globose (often oblique) nut with woody wall, provided with a ridge often apically enlarging into a wing (i.e. a samara).
Seed with a fairly thin testa, lacking albumen.
Seedling (of H. littoralis) with hypogeal germination; first 2 leaves opposite or subopposite, often scale-shaped, subsequent leaves arranged spirally.

Wood anatomy

Macroscopic characters

Mengkulang:

Heartwood brown to various shades of red-brown, sometimes with dark streaks, distinctly or indistinctly demarcated from the lighter sapwood (pale brown-yellow to reddish). Grain straight to shallowly interlocked.
Texture moderately coarse to coarse; fiddleback and ray figure present; wood more or less lustrous.
Growth rings usually indistinct; vessels visible to the naked eye, and sometimes with reddish, yellow or white contents; parenchyma and rays usually not distinct without a lens (except larger rays in some species); faint to distinct ripple marks usually present.

Dungun differs especially in the darker colour of the heartwood (dark brown, usually with a chocolate or even purple tinge), the often strongly interlocked grain, and the finer texture without ray figure.

Microscopic characters

Mengkulang and dungun:

Growth rings, if present, marked by marginal parenchyma bands and/or slight differences of vessel frequency, spacing of tangential parenchyma lines, and/or fibre wall thickness on either side of the ring boundary.
Vessels diffuse, 2-8(-25)/mm², solitary and in radial multiples of 2-5(-8), sometimes with narrow vessels in long radial tails or more rarely in clusters, round to oval, average tangential diameter 120-260μm; perforations simple; intervessel pits alternate, round to polygonal, 4-6(-8)μm; vessel-ray and vessel-parenchyma pits similar but half-bordered; helical thickenings absent, but vessel walls sometimes with fine spiral grooves intergrading with coalescent apertures; dark-staining gum-like deposits present in heartwood; tyloses absent.
Fibres (800-)850-1500(-2100)μm long, non-septate, mostly medium thick-walled, but ranging from very thin-walled to thick-walled, variable within and between species (see also large wood density ranges), with simple to minutely bordered pits mainly confined to the radial walls.
Parenchyma scarce, vasicentric (rarely tending to aliform), diffuse-in-aggregates or in fine discontinuous lines, and occasionally in marginal bands, in 2-4(-5)-celled strands. Rays 4-8/mm, of 2 distinct sizes, 1(-2)-seriate and 3-5(-9)-seriate, broad rays up to 2 mm high in some species, but tallest rays less than 1 mm in several others, heterocellular with one row of upright marginal cells to homocellular (mostly Kribs type heterogeneous III); sheath cells usually present.
Prismatic crystals often present in chambered axial parenchyma cells, less frequently also in non-chambered axial parenchyma and upright or procumbent ray cells; ray and parenchyma cells often with reddish-brown deposits.
Silica inclusions recorded in axial and ray parenchyma.
Traumatic gum ducts in concentric bands occasionally present.
Axial parenchyma strands, vessel elements and part of the rays weakly to distinctly storied, or all elements non-storied.

Species studied: H. aurea, H. borneensis, H. elata, H. javanica, H. littoralis, H. novoguineensis, H. simplicifolia, H. sumatrana, H. sylvatica.

Growth and development

The fruits are either dispersed by water (mangrove species) or by wind (inland forest species). The fruit of H. littoralis floats in water with the ridge upwards, and is impermeable to water. When washed up on a beach, the base of the fruit weakens, allowing moisture to penetrate. The thick, hard radicle opens the hard fruit wall and the primary root penetrates deeply into the soil. Fruits of other Heritiera species with large wings (e.g. H. javanica, H. simplicifolia) are wind-dispersed.

In H. littoralis the growth of the branches is rhythmic and the shoots are distinctly articulate. H. simplicifolia flowers at the beginning of the rainy season, but not every year. H. littoralis usually flowers at intervals throughout the year.

Other botanical information

Kostermans has united the genera Argyrodendron and Tarrietia with Heritiera. According to several botanists, Heritiera in the sense of Kostermans is too heterogeneous in several aspects, and in their view Tarrietia s.s., including Argyrodendron, is distinct from Heritiera s.s. Identifying and collecting Heritiera species often gives much trouble. Leaves may vary enormously within species; in trees up to 20 m tall they are often still completely different from those of mature trees. For instance, in young trees of H. simplicifolia the leaves may be palmately compound, whereas in old trees they are always simple. Many species are rare to very rare, plants are not easy to collect because of their habit (large trees with hard wood), they have very small flowers, and fruiting is often scanty.

The wood of Heritiera utilis (Sprague) Sprague and H. densiflora (Pellegr.) Kosterm. is exported from Africa. H. fomes Buch.-Ham. is extensively cut in India and Burma for its timber.

Ecology

H. littoralis grows in mangrove swamps on rocky and sandy coasts, often in drier sites and in the transition zone from mangrove to freshwater swamp. It is typically a tree of the banks of tidal rivers. Sometimes H. littoralis may make up 40% of the total stand, e.g. in Sarawak. It is often accompanied by Bruguiera parviflora (Roxb.) Wight & Arn. ex Griffith, Xylocarpus granatum Koenig, and Excoecaria agallocha L. Like H. littoralis, H. globosa grows behind the tidal zone of the mangrove belt, whereas some other species, e.g. H. novoguineensis, apparently prefer sites inundated by fresh water. Other species are found in inland forests, usually scattered and at low and medium altitudes (up to 600 m) in mixed dipterocarp forest. The different wood types may partially be determined by ecological conditions: mengkulang comes from inland forest species, dungun generally from mangrove swamp species.

Propagation and planting

H. javanica and H. simplicifolia can be propagated by sowing seeds in a nursery or by stump cuttings. Seedlings are transplanted into the field when 30-50 cm high. Spacing is 3 m × 4 m. The survival rate of planted stump cuttings is about 60%.

Silviculture and management

Natural regeneration techniques as used in regular management of mixed dipterocarp forest may be successful, but pure stands are probably not a good management target. Moreover, natural regeneration is usually scanty, especially in the inland forest species. In Africa H. utilis is artificially regenerated by strip planting.

Diseases and pests

Moth larvae and beetles of the families Curculionidae and Scolytidae may damage seeds of H. littoralis. High percentages of H. littoralis seeds may show evidence of borers. Research in Australia showed that very few seeds contain an intact embryo. There may be a significant amount of pre-dispersal predation by insects on developing seeds of H. littoralis. Moreover, crabs may damage seedlings.

Harvesting

An occasional defect of the log is said to be its brittle heart, up to a core of 15 cm.

Genetic resources

Many Heritiera species are apparently rare, and the more common species usually occur scattered in the forest, e.g. H. simplicifolia less than 1 tree/ha. As this makes these species liable to genetic erosion and possible extinction, steps should be taken to conserve and grow them.

Prospects

Mengkulang is a valuable timber, but the scattered appearance of the species in natural forests hampers its commercialization and endangers its survival if cut without management precautions. Research on silvicultural aspects, in particular growth rates and methods of vegetative propagation, is urgently needed.

Dungun is less valuable, but it is used extensively locally. In many places its habitat, i.e. mangrove forest, is threatened by uncontrolled exploitation, and needs integral protection.

Literature

Ashton, P.S., 1988. Manual of the non-dipterocarp trees of Sarawak. Vol. 2. Sarawak Branch for Forest Department, Sarawak.
Cockburn, P.F., 1976. Trees of Sabah. Vol. 1. Forest Department Sabah, Kuching. pp. 228-232.
Fundter, J.M., de Graaf, N.R. & Hildebrand, J.W., 1989. Heritiera simplicifolia (Masters) Kosterm. In: Westphal, E. & Jansen, P.C.M. (Editors): Plant Resources of South-East Asia. A selection. Pudoc, Wageningen. pp. 150-152 + fig.
Kostermans, A.J.G.H., 1959. A monograph of the genus Heritiera Aiton. Penerbitan 1. Madjelis Ilmu Pengetahuan Indonesia [Council for Sciences of Indonesia], Djakarta. 121 pp. Also in: Reinwardtia 4: 465-583 (1959).
Lomibao, B.A., 1978. Wood anatomy of Philippine mangrove species. Forpride Digest 7(1): 23-34.
Lopez, D.T., 1981. Malaysian timbers - mengkulang. Malaysian Forest Service Trade Leaflet No 47. Malaysian Timber Industry Board, Kuala Lumpur. 7 pp.
Martawijaya, A., Kartasujana, I., Kadir, K. & Prawira, S.A., 1986. Indonesian wood atlas. Vol. 1. Forest Products Research and Development Centre, Bogor. pp. 106-110.
Miles, D.H., Ly, A.M., Chittawong, V., de la Cruz, A.A. & Gomez, E.D., 1989. Toxicants from mangrove plants 6. Heritonin, a new piscicide from the mangrove plant Heritiera littoralis. Journal of Natural Products (Lloydia) 52: 896-898.
Robertson, A.I., Giddins, R. & Smith, T.J., 1990. Seed predation by insects in tropical mangrove forests: extent and effects on seed viability and the growth of seedlings. Oecologia 83: 213-219.
Wong, W.C., 1975. Particleboard from Heritiera javanica (mengkulang jari). Malaysian Forester 38: 278-283.

Selection of species

Authors

R.H.M.J. Lemmens (general part, selection of species),
I. Soerianegara (general part),
S.I. Wiselius (properties),
P. Baas (wood anatomy)