3685

5(1): Timber trees; Major commercial timbers

Parashorea Kurz

Journ. As. Soc. Beng. pt. 2, Nat. Hist. 39(2): 65 (1870).

DIPTEROCARPACEAE

x = 7; Parashorea densiflora: 2n = 14

Trade groups
— White seraya: moderately lightweight to medium-weight hardwood, e.g. Parashorea malaanonan (Blanco) Merr., Parashorea tomentella (Sym.) Meijer.
— Gerutu: moderately heavy hardwood, e.g. Parashorea densiflora v. Slooten & Sym., Parashorea lucida (Miq.) Kurz, Parashorea smythiesii Wyatt-Smith ex P. Ashton.

— White seraya: white lauan, Borneo cedar (En). Brunei: urat mata (Malay), perawan, sepit undang (Iban). Indonesia: urat mata, pendan (Kalimantan). Malaysia: urat mata (Sabah). Philippines: white lauan, bagtikan (general), malaanonang (Tagalog).
— Gerutu: heavy white seraya, heavy parashorea (En). Malaysia: meranti gerutu (Peninsular), urat mata batu (Sabah), urat mata bukit (Sarawak). Burma: tavoy wood, thingadu, kaunghmu. Laos: mai si, mai hao, mai nao. Thailand: khaikhieo (peninsular), kian-suai (Surat Thani). Vietnam: ch[of].

Parashorea consists of about 14 species which are widely distributed throughout continental South-East Asia (Burma, Thailand, Laos, southern Vietnam, southern China). Within the Malesian area a total of 10 species occur in Peninsular Malaysia (3 species), Sumatra (3 species), Borneo (6 species) and the Philippines (1 species).

White seraya is a general-purpose timber for light and medium-heavy construction but it is preferred for the manufacture of veneer and plywood. It is also applied for interior finish, light constructional work, cabinet and furniture, flooring for domestic purposes and recently also for the manufacture of fibreboard, particle board and wood-wool cement board. Since the timber is not durable and resists preservative treatment, it is not used in contact with water or the ground. Other applications of the wood are musical instruments, carvings, toys and novelties, turnery, boat planking and framing and ships decking (all under cover), fermentation vats, and for pulp and papermaking (often mixed with other hardwoods).
Like white seraya, gerutu is a general-purpose timber for medium-heavy construction but its main use is for veneer and plywood manufacturing. It is rated as non-durable to fairly durable, is resistant to preservative treatment, and is used mainly under cover and not in contact with the ground. It is best suited for interior construction and is chiefly used for flooring, joinery, cladding, shuttering and for making utility furniture and cabinets. Other applications are for railway sleepers, vehicle bodies, pallets, boxes and crates, poles and piles, staircases and tool handles (non-impact purposes). The wood is also suitable for hardboard and particle board manufacture as well as for pulp and papermaking (often mixed with other hardwoods).
Most of the species yield an oleo-resin which is used only locally for caulking boats and for torches. Probably because of its limited supply no collecting on a commercial scale has been reported.

Most white seraya timber on the world market originates from Sabah and Sarawak. Amounts exported are considerable, e.g. the export of round logs of white seraya from Sabah in 1987 was 1.53 million m³ with a value of US$ 168 million (average price 110 US$/m³), which makes it the second most important export timber of Sabah after 'red seraya' (light red meranti, Shorea spp.). The Philippines exported small amounts of this timber (from Parashorea malaanonan): 238 000 kg (with a value of US$ 53 000) in 1986. The majority of white seraya timber goes to Japan; smaller amounts are exported to the United States, European countries, and Korea. At present white seraya is exported from Sabah together with white meranti (Shorea spp.); in 1992 the export of logs was 635 000 m³ in this united trade group and of sawn timber 233 000 m³ with a total value of US$ 162 million.
The total production of gerutu is small, and the export is negligible. In Indonesia (Kalimantan) white seraya and (to a lesser extent) gerutu are used particularly in plywood production; no figures are available about their contribution to total plywood manufacture. In 1992 the export of sawn gerutu timber from Sabah was only 56 m³ with a value of US$ 20 000 (US$ 357/m³).

White seraya is a moderately light to medium-weight hardwood. The heartwood is pinkish or cream-coloured when freshly cut, weathering to straw-coloured or light brown on exposure, sometimes with a pinkish tinge, and not distinctly demarcated from the slightly paler sapwood. The density is 390—670 kg/m³ at 15% moisture content. The grain of the wood is interlocked, texture moderately coarse.
At 12% moisture content the modulus of rupture is 75—97 N/mm², modulus of elasticity 8900—13 950 N/mm², compression parallel to grain (31—)42—51 N/mm², compression perpendicular to grain 5—7 N/mm², shear 7—11 N/mm², cleavage 26—51 N/mm radial and 32—52 N/mm tangential, Janka side hardness 2620—4145 N and Janka end hardness 2760—3885 N.
The rates of shrinkage are moderate to high, from green to 12% moisture content 1.1—4.9% radial and 2.6—8.8% tangential. The timber air dries well and rapidly if properly stacked and well-ventilated, but boards may warp, check and stain if not enough care is taken. Boards of 25 mm thick take about 7.5 months to air dry from green to 15% moisture content. The kiln-drying properties are good, with only occasional cupping defects. Boards of 50 mm thick of Parashorea malaanonan kiln dry from 75% to 11% moisture content in 22 days. In Malaysia kiln schedule J is recommended. The movement of wood in service is minimal.
White seraya can be worked easily with hand and machine tools. It has little blunting effect on sawteeth and edges. The wood planes easily but quarter-sawn material has a tendency to tear. A cutting angle of 20° should be used to obtain the best results. A clear finish is obtained in most operations, provided the cutters are sharp. White seraya requires care in moulding to prevent arrises breaking away. The wood nails, glues, screws, chisels and turns very satisfactorily, and it polishes and varnishes well after filling. White seraya is not suited for steam bending. It can be sliced readily for veneer, and the veneer can be glued easily to give good-quality plywood. It can be chipped cleanly to produce hardboard of high quality. Wood dust may cause dermatitis.
White seraya is rated as non-durable in the tropics in exposed conditions or in contact with the ground, but as moderately durable in temperate climates. It is durable under cover and in dry conditions. The wood is susceptible to attack by pinhole borers, termites and marine borers, and the sapwood is also susceptible to powder-post beetles. The heartwood is resistant to impregnation with preservatives due to the presence of tyloses in the vessels, but the sapwood is permeable. For Parashorea malaanonan heartwood an absorption of 21—115 kg/m³ has been obtained using the open tank process, for Parashorea tomentella 6—53 kg/m³.
Gerutu is a medium-weight hardwood. The heartwood is very light brown to light bronze with a pinkish or yellowish tinge, darkening on exposure to deeper brown, distinctly demarcated from the light yellow-brown sapwood. The density is 640—865(—1050) kg/m³ at 15% moisture content. The grain of the wood is interlocked, texture coarse but even. Planed surfaces are slightly glossy and the radial surface has a stripe figure.
At 12% moisture content the modulus of rupture is c. 114 N/mm², modulus of elasticity 14 200 N/mm², compression parallel to grain 62 N/mm² and shear 15 N/mm².
The rates of shrinkage are moderate to high, from green to 12% moisture content 1.6—4.1% radial and 3.3—7.1% tangential, and from green to oven dry 4.1—5.1% radial and 6.6—8.1% tangential. Gerutu wood seasons easily but slowly without much degrade or distortion. The kiln-drying properties are rated as good, sometimes with slight cupping. In Malaysia kiln schedule C is recommended. The sapwood is susceptible to stain if not properly and carefully dried.
The working properties are more or less comparable to white seraya, but gerutu is less suited for veneer and plywood manufacture, as it is denser. The durability is slightly better than white seraya because of the greater density, but gerutu is rated as non-durable in exposed conditions or in contact with the ground under tropical conditions. The heartwood is extremely resistant to preservative treatment.

Large evergreen trees of 35—50(—60) m tall; bole tall, straight and cylindrical, branchless for 20—25 m and with a diameter of 100(—200) cm; buttresses large, rounded, slightly concave, hardly branched; bark surface distinctly mauve grey to purplish with narrow shallow fissures, with broad, smooth or flaking flat ridges, and numerous conspicuous large, pale, corky lenticels in the cracks, outer bark usually dark-coloured with brittle layers, inner bark yellow-brown or pinkish-brown grading to pale yellow at the cambium, sapwood pale yellowish, sometimes with a pink tinge; resin scanty, dirty cream to yellowish, exuding from rows or resin canals on cut surfaces; crown dense, becoming dome-shaped or hemispherical; main branches several to many, usually radiating from the bole apex, branches with alternating series of long and short internodes, twigs usually crowded to the ends of the branches; young parts and lower leaf surface usually pubescent. Leaves alternate, simple, broadly oblong-ovate, shortly acuminate, with an entire or wavy margin, pinnately veined; veins scalariform, usually straight, running in an acute angle from the midrib, with subpersistent plicate folding, no intermediate veins; young leaves white or glaucous beneath; petiole sometimes slightly swollen at base; stipules linear-lanceolate to hastate, early caducous, leaving short to amplexicaul scars. Inflorescence terminal or axillary, lax or dense, racemose (cymose in Parashorea macrophylla); bracts paired, small or large. Flowers secund or distichous, bisexual, actinomorphic, scented, nodding, ovate to subglobose in bud; calyx persistent, the 5 calyx lobes free down to the receptacle, in bud more or less equal, very narrowly imbricate; corolla 5-merous, contorted, petals falling separately (except in Parashorea stellata), oblong to broadly elliptical, white or yellow; stamens 15, much longer than the ovary; ovary (2—)3-locular, small, ovoid, glabrous or pubescent, style filiform, glabrous, sometimes thickened at base into a slender stylopodium, with a small, simple or slightly dilately truncate stigma. Fruit a large, ovoid to globose, pubescent, short-pedicelled, verrucose-lenticellate nut, free from the calyx; fruit calyx lobes enlarged, more or less equal and shorter than the nut or subequal, with 3 somewhat larger than the other 2 and spatulate, thickened and saccate at the valvate base; style remnant short, indistinct. Seedling with epigeal germination; with fleshy equal or subequal, deeply bilobed cotyledons well above soil level; seedling leaves long-petioled, often linear, in some species aciculate and unique for the family; first two leaves opposite, subsequent ones arranged spirally; older seedlings with subpeltate leaves.

— Macroscopic characters:
Heartwood light greyish-brown with a pinkish tinge, usually with irregularly spaced concentric dark (black or violet) stripes, often at intervals of 5—10 cm, not distinctly demarcated from the paler sapwood. Grain interlocked. Texture coarse; pale concentric bands, with white dots, distinct to the naked eye, irregularly spaced in cross-section. Growth rings indistinct.
— Microscopic characters:
Growth rings indistinct. Vessels diffuse, 2.5—7/mm², solitary and in radial multiples of 2(—3), maximum tangential diameter 300—350 µm; perforations simple; intervessel pits alternate, vestured, 6—8 µm; vessel-ray and vessel-parenchyma pits simple, round or oval or elongated; tyloses present, sometimes abundant. Vasicentric tracheids present. Fibres 1.3—2.1 mm long, thick-walled (2—5 µm), with small pits confined to the radial walls. Parenchyma vasicentric and confluent, with short wings, and abundantly apotracheally diffuse; also in irregularly spaced concentric bands surrounding the axial intercellular canals. Rays 5—8/mm or 3—5(—6)/mm (Parashorea smythiesii), 1—7(—8) cells wide, up to 2500 µm high, heterocellular with one and occasionally more rows of square and/or upright marginal cells (Kribs type heterogeneous III and II). Prismatic crystals present, in chambered axial parenchyma cells, in long chains of over 20 chambers, and in procumbent and chambered marginal ray cells. Axial canals of the concentric type distinct and surrounded by tangential parenchyma bands; horizontal canals found in fusiform rays (Parashorea smythiesii).
Species studied: Parashorea malaanonan, Parashorea smythiesii.
White seraya and gerutu can be distinguished from white meranti (Shorea spp.) by the presence of crystals in parenchyma and rays and the absence of silica, by the reddish-brown parenchyma and rays (yellow in white meranti) and by the more greyish wood colour with pink tinge.

Seedlings develop a strong taproot soon after germination, forming a few fibrous lateral roots later on. When the taproot is obstructed from penetrating the soil, forking or splitting results.
White seraya trees are fast growers. Planted trees of Parashorea malaanonan may reach a bole diameter of 90 cm in 40 years, but growth is usually slower. The average time for Parashorea tomentella trees to reach 75 cm diameter in forest in Sabah is estimated at 72 years. When, after selective logging, the non-commercial tree species are poisoned, the average diameter increment of Parashorea tomentella can be as much as 1.3 cm/year. Gerutu trees grow more slowly. The maximum bole diameter for planted Parashorea densiflora trees after 40 years is 54 cm, which still makes it a moderately fast grower. Growth rates in the forest, however, are considerably lower.
As in most dipterocarps, Parashorea trees flower at irregular intervals; flowering does not occur annually. In Peninsular Malaysia seed years occur every 2—5 years. Flowering and fruiting seasons last longer in wet and intermediate climatic regions than in the dry ones. As in many other canopy trees, the young trees do not flower at all until their sympodial crown is developed in direct sunlight. The winged fruits may be dispersed for comparatively small distances by wind, but most fruits fall within 60 m of the parent tree.

Parashorea is a small, homogeneous, but widely distributed genus, which is closely related to and superficially hardly distinguishable from Shorea. The characteristic large corky lenticels at the base of the bole and buttresses differ from the small and usually inconspicuous ones of the latter. The tendency of glaucescence of most of the lower leaf surfaces, the acute angle of the main veins with the midrib, the globose lenticellate nuts and the subequal fruit wings are other characteristics of Parashorea.
Embryo and seedling characters provide novel insights into the relationship and distinction of genera of Dipterocarpaceae. On this basis, the genus Parashorea seems to be most closely related to the former subgenus Rubroshorea Meijer of Shorea, which currently comprises the sections Rubella P. Ashton, Brachypterae Heim, Pachycarpae Heim, Mutica Brandis and Ovalis P. Ashton. Diagnostic characters within the genus Parashorea are the number of lateral leaf veins, pubescence of the leaf and length of the fruit wings and petiole.
The wood of white seraya is often confused with and used as a substitute for white meranti (Shorea spp.).

Parashorea spp. occur scattered and locally or sometimes abundantly and gregariously in a wide variety of forest habitats ranging from evergreen to semi-evergreen and dry deciduous dipterocarp forests in lowlands or hills and ridges up to 1400 m altitude. The habitats may be subject to occasional inundation, or be well-drained and even dry and rocky. Most species have a preference for clay soils. Parashorea spp. constitute one of the climax species in a dipterocarp rain forest.
In Sabah seven forest types (five in the lowlands and two in the hills) have been distinguished. White seraya abounds in three of the lowland types. These are: (1) Parashorea malaanonan forest where this species tends to single dominance; (2) Parashorea tomentella/Eusideroxylon zwageri Teijsm. & Binnend. forest where the first species is abundant; (3) Parashorea malaanonan/Dryobalanops lanceolata Burck forest where the first is one of the typical species. Parashorea spp. also occur in other forest types in Sabah, either reasonably commonly or rarely. In Sabah Parashorea malaanonan is locally the predominant timber species, sometimes accounting for almost 70% of the commercial trees in the forest. In natural forest in northern Sumatra Parashorea lucida may constitute 25% of the total number of trees.

Seeds are collected immediately after fruit fall. They should be properly packed in a moisture-holding medium such as moss, coconut fibre, sawdust or pulverized charcoal. The seeds should be sown rapidly as their viability is short. However, seeds of Parashorea densiflora can be stored in bags for 50—60 days. Fresh seeds of Parashorea tomentella may have a germination rate of 97%. Germination starts 2—20 days after sowing, with a peak at 10—12 days.
Wildlings are generally used for enrichment planting. They are collected in the forest and planted in polyethylene bags and kept in the nursery for about 8 weeks. Planting is usually done at the onset of the rainy season. Partial shade is needed while the plants are still young, i.e. from seedling to pole stage. Seedlings with a stem diameter of 1—2 cm and a height of 40—60 cm survive the best. Parashorea tomentella seedlings used for enrichment planting in Sabah showed a survival rate of 58% after 2 months. Spacing is often 4 m 4 m. In tests in the Philippines, Parashorea malaanonan could not be propagated successfully by air layering and shoot cuttings.

The overall management and development strategies for a dipterocarp forest also apply to white seraya and gerutu. A general forest management plan is prepared for this purpose incorporating the various components such as a logging plan, the annual allowable cut, cutting cycle and silvicultural treatment. At present, timber stand improvement and other silvicultural techniques in selectively logged dipterocarp forest with Parashorea are not applied or are limited to cutting of vines and removal of small defective trees and weeds. Enrichment planting is carried out on a very limited scale.
White seraya is locally abundant, in some areas of Sabah 25 trees/ha can be found, and seedlings of white seraya are there more abundant than any other tree species. In undisturbed forest, 17% of the initial number of seedlings was found to survive after 4 years. Seedling mortality is slightly higher after logging, but growth increases after opening of the canopy. White seraya usually regenerates sufficiently in logged-over forest.

Seedling diseases include root rot caused by fungi such as Fomes applanatum and damping-off caused by fungi of the genera Phytophthora, Pythium, Diplodia, Rhizoctonia and Fusarium. Root rot is often caused by stress of young plants and may be controlled by fertilization, prevention of root injuries, and by using fungicides. Damping-off can be controlled by not using heavy soil as potting medium, sterilizing soil, removing infected seedlings, and gradually exposing seedlings to full sunlight.
Beetles of the genus Adoretus (family Scarabaeidae) feed on seedlings, adults on leaves and tender shoots and larvae on roots and underground parts of the stem. Spraying with malathion 50EC or sevin WP (1.6 ml/l) can solve the problem. Attack of the bark engraver Xyleborus ursus can be controlled by injecting a solution of dieldrex 15 into the tunnels. The borer Hoplocerambix spinicornis may cause severe damage to logs of living and felled trees. Snails feed voraciously on seedlings, being active at night and during rainy and cloudy days. A bait consisting of calcium arsenate, metaldehyde and fine rice bran (5:2:100), moistened by water, has been found very effective.

Trees are usually recommended to be felled according to selective logging systems, as commonly practised in dipterocarp forest. Mature and over-mature trees are cut and removed from the forest, and uninjured, healthy residuals are left. A tree marking system is used, whereby the trees to be felled are marked by arrows showing the direction of the fall, and the trees to be retained are marked by numbers and bands. A formula for determining the allowable cut is followed. Felling rules and yarding techniques are prescribed and implemented to insure a good balance of satisfactory log production and an adequate number of residual trees for the next felling operation on a prescribed cutting cycle. However, the selective logging system has to be proven economically and silviculturally workable in mixed dipterocarp forest in South-East Asia.
Brittle heart is often present in the logs to some extent. In general, logs of white seraya can be transported by river, but gerutu logs sink in water. The timber should be extracted rapidly from the forest to prevent severe damage by pinhole borers.

The supply of white seraya is still abundant, particularly in Sabah, Sarawak and parts of Indonesia. Gerutu, however, appears to be limited and scattered. Continued exploitation of gerutu will make it prone to genetic erosion and possible extinction.

White seraya may be well suited for felling under selective cutting systems. Its natural regeneration is satisfactory, and prospects for sustained yield are good. Growth rates are comparable to those of red and white meranti, which often co-occur with white seraya in the forest. This could make it easier to manage forests for an optimal production of white seraya and meranti. Appropriate forest management techniques that aim at sustained yield through natural or artifical regeneration are of major concern.

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.
Browne, F.G., 1955. Forest trees of Sarawak and Brunei and their products. Government Printing Office, Kuching. pp. 126-129.
Burgess, P.F., 1966. Timbers of Sabah. Sabah Forest Records No 6. Forest Department, Sabah, Sandakan. pp. 140-154.
Choo, K.T. & Lim, S.C., 1986. Malaysian timbers - gerutu. Timber Trade Leaflet No 101. Malaysian Timber Industry Board, Forest Research Institute Malaysia. 8 pp.
Dahms, K.-G, 1982. Asiatische, Ozeanische und Australische Exporthölzer [Asiatic, Pacific and Australian export timbers]. DRW-Verlag, Stuttgart. pp. 252-256.
Durand, P.Y., 1985. Commercial nomenclature of Shorea and Parashorea, white lauan and white seraya. Revue Bois et Forêts des Tropiques 210: 59-66, 79-88.
Fox, J.E.D., 1983. The natural vegetation of Sabah, Malaysia 2. The Parashorea forests of the lowlands. Tropical Ecology 24: 94-112.
Fox, J.E.D. & Chai, D.N.P., 1982. Refinement of a regenerating stand of the Parashorea tomentella/Eusideroxylon zwageri type of lowland dipterocarp forest in Sabah - A problem in silvicultural management. Malaysian Forester 45: 133-183.
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 and London. pp. 253-254.
Liew, T.C. & Wong, F.O., 1973. Density, recruitment, mortality and growth of dipterocarp seedlings in virgin and logged-over forest in Sabah. Malaysian Forester 36: 3-15.

W.M. America (general part, selection of species), D.S. Alonzo (properties) & S. Sudo (wood anatomy)

Parashorea aptera
Parashorea densiflora
Parashorea lucida
Parashorea macrophylla
Parashorea malaanonan
Parashorea parvifolia
Parashorea smythiesii
Parashorea stellata
Parashorea tomentella

America, W.M., Alonzo, D.S. & Sudo, S., 1993. Parashorea Kurz. In: Soerianegara, I. and Lemmens, R.H.M.J. (Editors): Plant Resources of South-East Asia No 5(1): Timber trees; Major commercial timbers. PROSEA Foundation, Bogor, Indonesia. Database record: prota4u.org/prosea

The following species in this genus are important in this commodity group and are treated separatedly in this database:
Parashorea aptera
Parashorea densiflora
Parashorea lucida
Parashorea macrophylla
Parashorea malaanonan
Parashorea parvifolia
Parashorea smythiesii
Parashorea stellata
Parashorea tomentella