Shorea (white meranti) (PROSEA)

Plant Resources of South-East Asia
Introduction

Shorea Roxb. ex Gaertner f. (white meranti)

Protologue: Fruct. 3: 47 (1805).

Family: Dipterocarpaceae

Chromosome number: x= 7; 2n= 14 for the majority of species, S. resinosa: 3n= 21

Trade groups

White meranti: lightweight hardwood, e.g. Shorea assamica Dyer, S. bracteolata Dyer, S. henryana Pierre, S. javanica Koord. & Valeton, S. roxburghii G. Don.

Vernacular names

White meranti

Indonesia: meranti putih (general), damar putih (Sumatra), damar tenang putih (Moluccas)
Malaysia: meranti pa'ang, temak (Peninsular), raruk, melapi (Sarawak), melapi (Sabah)
Philippines: yellow lauan, manggasinoro (both names also used for yellow meranti)
Cambodia: lum'-baô
Thailand: phayom (central), saya-khao (Narathiwat), kiam-khanong (Nakhon Ratchasima, Prachin Buri)
Vietnam: sến, vên vên.

Origin and geographic distribution

Shorea consists of about 194 species, 163 of which occur in Malesia. The genus is distributed from Sri Lanka and India through Indo-China towards Malesia. Within Malesia the species occur eastward to the Moluccas. The genus is absent from the Lesser Sunda Islands but fossil wood has been recorded for Timor.

The species belonging to the white meranti group occur throughout the range of the genus. Within Malesia 22 species are found distributed as follows: Peninsular Malaysia (11 species), Sumatra (9 species), Borneo (13 species), the Philippines (3 species), Java (1 species), Sulawesi (1 species, possibly 2), and the Moluccas (2 species).

Uses

Shorea is economically the most important timber genus in the Asian humid tropics. White meranti is used as a light construction timber. The wood is not very durable and should, therefore, not be used in contact with the ground unless treated. Because of the high silica content, white meranti is not very popular as a sawn timber but it has been used for a wide variety of purposes such as door and window frames, posts, beams, joists, rafters, planking, light flooring, ceiling, furniture, interior and shop fitting, vehicle bodies, sporting goods, vats, wine casks, food containers, stair stringers, and for ship and boat building.

The most important use of white meranti is as a plywood and veneer timber, for which it has excellent properties and is highly preferred. The wood is satisfactorily used for pulp in the manufacture of paper too.

The bark of several species has been stripped and locally used for house walls and for the manufacture of baskets and bins. The trunk yields a usually clear, pale yellow dammar which might be suitable for varnish, but is generally of inferior quality and used locally for torches.

Production and international trade

For Indonesia, only export figures for meranti as a whole are available. The export of sawn meranti timber from Indonesia increased slightly from 1.3 million m³ (with a value of US$ 249 million) in 1987, to 1.4 million m³ (with a value of US$ 301 million) in 1989. Much more important in Indonesia is the production and export of plywood (estimated export value in 1990: US$ 3000 million), in which white meranti wood contributes an important part, together with red meranti (which contributes the major part), and keruing (Dipterocarpus spp.).

Export of white meranti from Peninsular Malaysia is not significant, but in Sarawak and Sabah "melapi" is a fairly important export timber. In 1987 export of round logs from Sabah was 260 000 m³ with a value of US$ 27 million. White meranti is at present traded from Sabah together with white seraya (Parashorea spp.) in one trade group; in 1992 635 000 m³ of logs and 233 000 m³ of sawn timber was exported in this combined trade group with a total value of US$ 162 million. No export statistics are available from other countries.

Properties

White meranti is a lightweight hardwood. The heartwood is yellowish-white and indistinct from the sapwood when freshly cut, but gradually becomes yellowish-brown or light brown and slightly more distinct from the sapwood on exposure. The density is (380-)495-870(-945) kg/m³ at 15% moisture content. The grain of the wood is usually interlocked, texture moderately coarse but even. The planed surface is lustrous, often with subtle ribbon figures.

At 15% moisture content, the modulus of rupture is 57-132 N/mm², modulus of elasticity 9500-19 400 N/mm², compression parallel to grain 29-67 N/mm², compression perpendicular to grain 4-11 N/mm², shear 5-14 N/mm², cleavage 41-58 N/mm radial and 43-60 N/mm tangential, and Janka side hardness 2765-9210 N.

The rates of shrinkage are low to moderate, from green to 15% moisture content 0.6-1.8% radial and 1.4-3.0% tangential, and from green to oven dry 2.5-3.5% radial and 5.7-7.5% tangential. White meranti dries fast to moderately slowly and without defects, except for occasional slight cupping, bowing and end and surface checks. It takes about 3 months and 5 months respectively to air dry boards of 15 mm and 40 mm thick. In Malaysia kiln-drying schedule J is recommended. The kiln-drying period of 25 mm thick boards is approximately 5 days.

The silica present in white meranti easily blunts cutter-tool edges. For sawing the logs, band saws need to have specially inserted teeth such as the tungsten-carbide type. Resawing is slightly difficult and the sawn surface tends to be woolly; cross cutting is also slightly difficult and sometimes difficult (S. henryana). Planing of air-dry timber is moderately difficult and the planed surface is rough for S. bracteolata and S. henryana but moderately smooth for S. hypochra and S. roxburghii. Boring is generally easy, with the exception of S. henryana, and the bored surface is rough. Turning is moderately easy to moderately difficult and gives a rough surface. The resistance to splitting when nailed is generally poor.

The creamy white and uniform colour, even texture and good gluing properties make white meranti a highly preferred timber for plywood production. The veneer is generally tight, smooth and of reasonably good quality; it shows few drying defects. However, the high silica content of the wood makes it difficult to saw. Experimental particle boards of 610 kg/m³ made with 8% resin and 1% wax have properties exceeding those stipulated in the British standards.

White meranti is moderately durable. Graveyard tests with stakes in Malaysia indicated that the average service life in contact with the ground ranged from 2.6 years for S. bracteolata to 4.5 years for S. roxburghii. Under temperate conditions the service life in contact with the ground is 5-10 years. The sapwood appears to be readily attacked by pinhole borers after felling. Discoloration by blue stain fungi is common. The timber is not resistant to marine borer attack, even though it has a high silica content. Drastic schedules must be used to impregnate white meranti timber with preservatives, and even then the absorption of chemicals is low.

Wood of S. bracteolata contains 54% cellulose, 24% lignin, 16.5% pentosan and 1.4% ash. The silica content is c. 1.1% for S. bracteolata and up to nearly 2% for S. resinosa. The solubility of S. bracteolata wood is 6.0% in alcohol-benzene, 0.9% in cold water, 4.5% in hot water and 11.4% in a 1% NaOH solution. The energy value is 20 120 kJ/kg.

Description

Medium-sized to very large trees up to 60 m tall; bole straight, cylindrical, branchless for up to 30(-37) m and with a diameter of up to 180(-225) cm; buttresses prominent, up to 3.5(-4.8) m high; bark surface with irregular section fissures, rarely scaly, grey or light brown, outer bark usually thick, chocolate brown, inner bark laminated with bands of orange-yellow (rarely pink) and whitish tissue, exuding a clear, yellow resin; mature crown hemispherical or dome-shaped, sympodial.
Leaves alternate, simple, entire, glabrous or with stellate hairs, pinnately veined with scalariform tertiary venation and an obscure midrib, often glaucous on the lower surface; stipules and bracts often large and more or less persistent.
Inflorescence terminal or axillary, paniculate.
Flowers secund or distichous, bisexual, 5-merous, actinomorphic, scented; calyx lobes free, hirsute; petals broadly elliptical to ovate-lanceolate, loosely connate at base, white often tinged with pink, the outer surface hirsute; stamens 15-30, the anthers with 4 pollen sacs, narrowly oblong to linear, with prominent, scabrous or glabrous appendages; ovary without a distinct stylopodium, tomentose or glabrous; style longer than the ovary.
Fruit usually shortly stalked; the outer 3 calyx lobes much elongated, more or less thickened and saccate at base.
Nut 1-seeded, free from the calyx, subglobose to ovate, sharply pointed.
Seedling with epigeal germination; pericarp splitting irregularly; cotyledons usually pale yellow to reddish; first two leaves opposite, subsequent leaves arranged spirally, often larger than those on mature trees.

Wood anatomy

Macroscopic characters

Heartwood almost white when freshly cut but becoming yellowish or even brownish with age, lacking a pink tinge; sapwood pale yellow when freshly cut but gradually turning light yellow-brown on exposure, 5-7 cm wide, fairly distinctly demarcated from the heartwood in dry timber.
Grain usually interlocked to deeply interlocked, sometimes wavy, rarely straight.
Texture moderately coarse and even, finer than most red meranti; vague ribbon figure present on radial surfaces.
Freshly cut wood with a characteristic fresh, sappy smell, dried wood without odour and taste.
Growth rings indistinct or absent; vessels markedly reticulate in arrangement, visible to the naked eye, tyloses usually sparse and vessels conspicuously open.
Parenchyma sparse to moderately abundant, often bright yellow, fairly conspicuous, especially on wetted cross-section.
Rays just visible to individually distinct to the naked eye on end surfaces, individually distinct to the naked eye as short lines darker in colour than the ground tissue of fibres on tangential surfaces, distinct but not conspicuous on radial surfaces.
Ripple marks usually absent or indistinct to the naked eye.
Intercellular canals in more or less continuous tangential lines, usually smaller than the vessels, barely visible to the naked eye on all surfaces, filled with white contents.

Microscopic characters

Growth rings indistinct or absent.
Vessels diffuse, 2-8/mm², mostly 4-6/mm² (in S. hypochra 5-20/mm²), mostly solitary but occasionally in radial multiples of 2-3, sometimes arranged in oblique or almost tangential lines, round to slightly oval, 100-300(-400) μm in tangential diameter, average length of vessel elements 350-800 μm; perforation plates simple; intervessel pits alternate, vestured, 2.5-6μm; vessel-ray pits and vessel-parenchyma pits large (over 10μm in diameter), round and gash-like.
Fibres 900-1600 μm long, non-septate, moderately thick-walled, occasionally thin-walled, with simple to minutely bordered pits mainly confined to the radial walls.
Parenchyma predominantly paratracheal, apotracheal parenchyma sparse; paratracheal parenchyma incompletely vasicentric, often aliform and locally confluent; apotracheal parenchyma diffuse and diffuse-in-aggregates and in tangential lines surrounding vertical resin canals, sometimes in short, fine, irregularly spaced lines.
Rays 4-8(-12)/mm, commonly multiseriate (4-10-seriate), 30-100 μm wide, low to extremely low (130-1700 μm, average 400 μm), generally distinctly lower than in other dipterocarps, with 1-2(-4) rows of marginal cells (Kribs type heterogeneous III, rarely II).
Crystals absent.
Silica bodies characteristically abundant in ray cells.
Vertical resin canals in more or less continuous tangential lines, round and bead-like, filled with white resin.
Parenchyma storied.

Species studied: S. assamica, S. bracteolata, S. gratissima, S. hypochra, S. javanica, S. ochracea.

White meranti differs from white seraya (Parashorea spp.) by the absence of crystals, the presence of silica and the often distinctly yellow parenchyma and rays. It can be distinguished from yellow meranti by the wood colour and lustre, and by the absence of radial intercellular canals.

Growth and development

Seedlings need shade until they reach a height of about 1.5 m. Then the shade trees can be gradually removed to provide sunlight. The young trees show a tendency to form multiple leaders when exposed to full sunlight. Mycorrhizal infection promotes growth considerably. Five species of common ectomycorrhizal fungi associated with the roots of S. javanica have been identified: Amanita hemibapha, Cantharellus cibarius, Lactarius sp., Russula sp. and Scleroderma sp. In a 60-year-old forest plantation, 84% of the trees of S. bracteolata were found to be infected by mycorrhizae.

In general, the growth of white meranti trees is moderately fast. Trees of S. javanica may reach a height of 40-50 m in 50 years. Measurements of planted trees in Malaysia showed that the maximum diameter after 40 years can be as much as 86 cm for S. assamica, 65 cm for S. resinosa and S. roxburghii, 55 cm for S. agamii, and 53 cm for S. bracteolata.

The formation of pro-embryos and the occurrence of multiple seedlings was demonstrated in S. agamii and S. resinosa, suggesting apomixis.

S. roxburghii is fire-tolerant and shows fire-resistant adaptations in India and Burma, just like S. robusta Gaertner f. It has a thick bark and is deciduous during the dry period. It forms co-dominant or almost pure stands, and trees flower in most years, shortly before, during or after leaf fall. In seedlings the roots often become deep and extensive before a permanent leader shoot is established, and mature trees sucker readily in response to damage.

Other botanical information

Anatomical features of the wood and bark, as well as anther characters, provide useful evidence for the classification of species at infrageneric level. The division of the genus Shorea into 4 major timber groups (red meranti, white meranti, yellow meranti and balau) coincides in broad outline with the division of the genus into botanical sections. Timbers belonging to the white meranti group belong to the section Anthoshorea Heim, which is related to the section Doona (Thwaites) P. Ashton from Sri Lanka, the red meranti section Brachypterae Heim, and the genus Dryobalanops.

S. contorta S. Vidal, belonging to the section Pentacme (A.DC.) P. Ashton, is sometimes considered to be a white meranti. Its wood ("white lauan") often has a pink tinge, and this species is treated here as red meranti.

Ecology

Shorea species are confined to tropical climates with a mean annual rainfall exceeding 1600 mm and with a dry season of less than 6 months. Most species occur below 1000 m altitude. The largest numbers of species and of individuals are found on deep, well-drained yellow or red soils in the lowland. In general, white meranti is more abundant in seasonal than in aseasonal forests.

Propagation and planting

Seeds rapidly lose their viability. Time of seed collection is important for the germination success. Mature seeds germinate well (about 96%) immediately after collection, but storage often causes rapid deterioration. However, seeds collected 4 and 2 weeks before maturity show only 66% and 79% germination immediately after collection, but loss of viability of immature seeds during storage is much less. Storage in sealed bags gives good results. Experiments in Thailand showed that seeds of S. roxburghii stored for 56 days at 15 °C maintain 90% germination. Storage in ventilated containers or sealed bags at 16-21 °C enables seeds to survive for up to 10 months with over 50% viability. Seeds of other species can probably be stored for only comparatively short periods. Germination tests showed that S. javanica seeds can best be kept at 20-27 °C and 60-67% relative humidity. The weight of 1000 nuts of S. javanica (fruit wings removed) is about 1200 g, that of 1000 nuts of S. assamica is about 1050 g.

Stem cuttings of S. bracteolata treated with growth regulators and planted in coarse river sand may show 100% rooting success. The survival of stump transplants (defoliated seedlings without the top half of the leader shoot) is correlated with their starch content. The starch content of seedlings of S. hypochra and S. roxburghii is comparatively high, and they are recommended for bare-root planting. For bare-root planting of S. roxburghii at least one node must be retained above the cotyledons. Stump transplants can be stored in plastic bags for over 7 months at 25 °C and can be vegetatively propagated by cuttings or by planting horizontally to make several shoots.

S. roxburghii has also been successfully propagated in vitro. Development of axillary shoots was induced in embryonic axes on a modified Murashige and Skoog medium containing 5 mg/l of 6-benzyl-aminopurine. Excised axillary shoots rooted vigorously on filter paper in a liquid medium containing naphthalene-acetic acid and indole-butyric acid.

The best planting material is 50-100 cm tall seedlings raised in the nursery, wildlings, or stump cuttings obtained from about 1.5-year-old nursery stock. Planting distance is usually 3 m × 3 m.

Silviculture and management

Natural regeneration of white meranti species in the forest is often gregarious. However, in logged-over forest, enrichment planting may be necessary to maintain an important proportion of white meranti in the forest. When shade trees such as Paraserianthes falcataria (L.) Nielsen are used, plantations can be established in deforested areas. White meranti is planted when the shade trees are 3-5 years old.

In southern Sumatra a multistorey agroforestry system has been in use for decades, in which dammar from S. javanica is produced, and other crops, such as coffee, are also grown. The trees grow in a rotation of about 50 years and in this period they form a stand 40-50 m high. The dammar-producing trees are often planted mixed with other useful tree species (e.g. fruit-producing trees) or bamboos and rattans. In 1954 about 70 ha were in production for dammar in southern Sumatra.

Diseases and pests

Plantations of S. javanica easily become infested by galls caused by the bacterium Phytomonas tumefaciens. The gall disease occurs first on 1-2-year-old seedlings, and is not necessarily fatal, as new sprouts arise when the diseased part of the plant is removed. Pathogenic fungi of Fusarium cause sapling defoliation and death of S. javanica. Beetles of the family Scolytidae can cause damage to fruits.

Harvesting

In mixed dipterocarp forest in Indonesia trees of over 50 cm in diameter are harvested, and at least 25 healthy trees/ha of 20-50 cm in diameter are left for future cut. Since the logs float, they can be transported by river.

Genetic resources

Just as in other meranti trade groups, white meranti includes several species, some of which are common and widely distributed (e.g. S. assamica, S. bracteolata), whereas other species occur only locally or scattered. When large-scale logging is practised without distinction at species level, certain species can become endangered, such as S. gratissima in Peninsular Malaysia, S. polita in the Philippines, or S. retinodes in Sumatra.

Prospects

White meranti seems to have good potential for large-scale enrichment planting and for the establishment of timber plantations, especially for plywood production. Several species (e.g. S. roxburghii) are comparatively easy to propagate, and white meranti often grows fast. Propagation techniques and artificial regeneration in the forest are still in a trial stage, and need more research.

Literature

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. 237-552.
Corbineau, F. & Come, D., 1989. Experiments on germination and storage of the seeds of two dipterocarps: Shorea roxburghii and Hopea odorata. Malaysian Forester 49: 371-381.
Martawijaya, A., Kartasujana, I., Kadir, K. & Prawira, S.A., 1986. Indonesian wood atlas. Vol. 1. Forest Products Research and Development Centre, Bogor. pp. 88-92.
Mori, T., 1981. Bare-root planting of Malaysian dipterocarps. Effect of starch reserves in stem on survival and growth of transplants. Bulletin of Forestry and Forest Products Research Institute, Japan No 316: 91-115.
Nuhamara, S.T., 1987. Multidisciplinary research on Shorea javanica 3. Mycorrhizae in agroforestry: a case study. Biotropica 1: 53-57.
Panochit, J., Wasuwanich, P. & Hellum, A.K., 1986. Collection and storage of seeds of Shorea roxburghii G. Don. Embryon 2(1): 62-67.
Sasaki, S., 1980. Growth and storage of bare-root planting stock of dipterocarps with particular reference to Shorea talura. Malaysian Forester 43: 144-160.
Scott, E.S., Rao, A.N. & Loh, C.S., 1988. Production of plantlets of Shorea roxburghii G. Don from embryonic axes cultures in-vitro. Annals of Botany, London 61: 233-236.
Tompsett, P.B., 1985. The influence of moisture content and storage temperature on the viability of Shorea almon, Shorea robusta and Shorea roxburghii seed. Canadian Journal of Forest Research 15: 1074-1079.
Torquebiau, E.F., 1984. Man-made dipterocarp forest in Sumatra. Agroforestry Systems 2: 103-127.

Selection of species

Authors

K.M. Kochummen (general part),
W.C. Wong (properties),
J.M. Fundter (wood anatomy) &
M.S.M. Sosef (selection of species)