Cratoxylum (PROSEA)

Plant Resources of South-East Asia
Introduction

List of species

Cratoxylum Blume

Protologue: Verh. Batav. Genootsch. Kunsten 9: 172, 174 (1823).

Family: Guttiferae

Chromosome number: x= probably 7; C. cochinchinense: n= 11, C. formosum: 2n= 14

Trade groups

Geronggang: lightweight hardwood, e.g. Cratoxylum arborescens (Vahl) Blume.

Derum: medium-weight hardwood, e.g. C. cochinchinense (Lour.) Blume, C. formosum (Jack) Dyer.

Vernacular names

Geronggang

Brunei: serungan
Indonesia: gerunggang (general), madang baro (Sumatra), adat (Kalimantan)
Malaysia: gonggang (Peninsular, Sarawak), serungan (Sabah)
Thailand: kalong-ngae, ngong-ngang (Narathiwat).

Derum

Brunei: pelawan
Indonesia: mampat (Sumatra), butun (Kalimantan)
Malaysia: mempat (Peninsular), entemu (Sarawak), serungan batu (Sabah)
Philippines: salinggogon (Pilipino)
Laos: tiou-tiou
Thailand: tiu-kliang (northern), tiu-khao (Bangkok)
Vietnam: thành ngạnh.

Origin and geographic distribution

Cratoxylum comprises 6 species and occurs from eastern India through mainland South-East Asia towards the Malesian area. In Malesia it is encountered in Peninsular Malaysia, Sumatra, Borneo, Java, the Lesser Sunda Islands, Sulawesi and the Philippines.

Uses

Geronggang is a non-durable, general-utility timber used for light construction under cover. It is suitable for boards, cladding, shelving, cheap and light flooring and furniture, interior joinery, shelving, shuttering, panelling, mouldings, concrete forms and interior parts of ships. Being light, the wood is especially suited for boxes and other light packing cases. On a local scale geronggang is used for posts, beams, joists and agricultural implements. When impregnated, geronggang wood makes good roofing shingles. It is sometimes used as a substitute for red meranti except for purposes where strength is required and has also been traded mixed with light red meranti. Good-quality particle board, wood-wool cement board and standard-quality hardboard can be manufactured from geronggang. The wood is suitable for the production of pulp.

Derum timber is not commercially exploited due to its scarcity. There is a local demand for the timber for purposes such as poles and local house construction. The wood is sometimes handsomely figured and suitable for turnery, carving and furniture.

Both geronggang and derum wood are favourites for firewood and charcoal manufacture. Sometimes the bark and base of the trunk produces a resinous exudate which is used as a remedy for scabies and leg wounds. A decoction of the bark, roots and leaves has been used against stomachache and fever. The leaves have been chewed as being salutary. Several species are favoured as ornamental trees.

Production and international trade

Geronggang is traded in comparatively small amounts. Peninsular Malaysia exports sawn timber, particularly to Singapore. In 1983 5700 m³ of saw logs was exported, with a value of US$ 260 000, and in 1984 1700 m³ with a value of US$ 72 000. Sabah exported only 185 m³ (worth US$ 15 500, US$ 84/m³) in 1987, but in 1992 the export had increased to 8500 m³of logs and 5000 m³ of sawn timber with a total value of US$ 1.5 million. No export statistics are available from other countries.

Properties

Geronggang is a lightweight hardwood. The heartwood is light brick-red to deep pink, gradually darkening on exposure to reddish-brown, distinctly demarcated from the yellow, sometimes pink or orange sapwood. The density is 350-610(-710) kg/m³ at 15% moisture content. The grain is straight to interlocked, texture moderately coarse but even. Planed surfaces are lustrous, lacking a distinct figure.

At 15% moisture content the modulus of rupture is c. 60 N/mm², modulus of elasticity 10 100 N/mm², compression parallel to grain 29 N/mm², compression perpendicular to grain 3 N/mm², shear 4-6 N/mm², cleavage 44 N/mm radial and 51 N/mm tangential, Janka side hardness 1750 N and Janka end hardness 2400 N.

The rates of shrinkage are moderate, from green to 15% moisture content 2.2-2.6% radial and 4.2-4.7% tangential. The timber seasons rapidly without significant defects; end checks are the main ones. Boards of 2.5 cm thick take about 2 months to air dry, boards of 4 cm thick slightly longer. In Malaysia kiln schedule E is recommended.

Geronggang is easily sawn in green as well as in air-dry condition. The wood usually contains silica and saws are blunted fairly rapidly. It can be planed to a smooth surface, except on radial surfaces of green wood. The wood is easy to bore and turn, but the quality of finish is rough. Tests on machining properties showed poor results in mortising, shaping and sanding. The wood is easy to nail without splitting and, after some filling, it takes an attractive and smooth polish. Geronggang can be peeled at a 90° peeling angle to produce good veneer, without pretreatment. Gluing with urea-formaldehyde with the addition of 20% wheat flour gives good plywood.

Geronggang is rated as non-durable. Untreated stakes have a service life in contact with the ground of less than one year to 2 years. The wood is susceptible to termite and ambrosia beetle attack. It is easily treated with preservatives using the open tank process. It absorbs 320-480 kg/m³ of creosote. Laboratory tests indicate, however, that it is difficult to treat with CCA preservative by the full-cell process. Treated wood can be very durable.

Wood of C. arborescens contains 53% cellulose, 22% lignin, 18.5% pentosan, 1.0% ash and 0.1% silica. The solubility is 4.1% in alcohol-benzene, 0.7% in cold water, 5.1% in hot water and 14.2% in a 1% NaOH solution. The energy value is 19 900 kJ/kg.

Derum is a moderately heavy hardwood. The heartwood is brown with a purple tinge and is not clearly differentiated from the sapwood. The density is (580-)700-950(-1050) kg/m³ at 15% moisture content. The grain is straight or interlocked, texture moderately fine and even.

At 15% moisture content, compression parallel to grain is 48 N/mm², compression perpendicular to grain 9.5 N/mm², and shear 14.5 N/mm².

The rates of shrinkage are moderate, from green to 15% moisture content 2.3% radial and 4.6% tangential. Derum seasons fairly slowly but without serious defects. Boards of 15 mm thick take about 3 months to air dry, boards of 40 mm thick 6 months.

Derum is moderately difficult to difficult to resaw; cross cutting is rated as easy to difficult. Planing is fairly easy, producing smooth surfaces.

Logs of C. formosum were peeled successfully into 1.6 mm thick veneer in experiments in Malaysia, but with slight difficulty into 3.2 mm thick veneer. The veneer dries at a moderate rate with only slight defects. It was glued with urea-formaldehyde adhesive to produce good-quality plywood; phenol-formaldehyde adhesive is not suitable. The wood is moderately durable in contact with the ground or when exposed to the weather.

Description

Deciduous or evergreen trees or shrubs of up to 35(-50) m tall; bole straight or of rather poor shape, branchless for up to 27 m, up to 60(-100) cm in diameter, without buttresses, sometimes slightly fluted at base; bark surface smooth or papery-scaly to fissured, at the base of the stem exuding a yellow or orange to red resinous translucent sap hardening black; crown rather compact and dark; branches compressed, ridged.
Leaves simple, opposite or rarely subopposite, decussate, sessile or shortly petioled, often with minute translucent glandular dots; stipules absent.
Inflorescence a terminal panicle or axillary raceme or cyme, sometimes flowers single.
Flowers bisexual, actinomorphic, 5-merous, sometimes heterodistylous, scented; sepals coriaceous, persistent in fruit, with longitudinal pale or black glandular lines or dots; petals caducous to subpersistent, obovate, deep crimson to pink or white, with red or black glandular dots or lines, sometimes with a scale-like, nectariferous appendage at the base; stamens in 3 bundles, with numerous, dorsifixed, crimson to white anthers and alternating with 3 staminodial scales, filaments slender, united for over half their length; ovary superior, incompletely 3-celled, styles 3, free, slender, glabrous, with small, capitate stigmas; ovules 4 or more on the basal half of each placenta.
Fruit a more or less woody, 3-valved, dehiscent capsule, the columella-like placenta persistent at base and becoming woody, septa attached to the columella at base, free in the distal part.
Seed imbricate, cylindrical to ovoid, winged unilaterally or all around.
Seedling with epigeal germination.

Wood anatomy

Macroscopic characters

Geronggang:

Heartwood light brick-red to dark pink when fresh, darkening on exposure to medium brown with a reddish tinge, generally distinct from the yellowish sapwood.
Grain generally straight, sometimes interlocked.
Texture moderately coarse but uniform.
Growth rings indistinct or absent.
Vessels visible to the naked eye.
Tyloses common to infrequent, visible with hand lens.
Parenchyma not visible with hand lens.
Rays not visible to the naked eye, barely distinct with hand lens.
Ripple marks absent.

Derum:

Heartwood light brown to medium brown, sometimes with a purple tinge, but rarely with red or pink highlights, not distinct from the sapwood.
Grain generally straight, sometimes interlocked.
Texture moderately fine and uniform.
Growth rings indistinct or absent.
Vessels not visible to the naked eye.
Tyloses generally absent.
Apotracheal banded parenchyma abundant and distinct with hand lens.
Rays not visible to the naked eye, barely distinct with hand lens.
Ripple marks absent.

Microscopic characters

Geronggang:

Growth rings indistinct or absent.
Vessels diffuse, 7-10/mm², occasionally in diagonal pattern, but mostly in short radial multiples (sometimes in radial multiples of 4 or more and then a large vessel is aligned with several abnormally small vessels), 100-200μm in diameter; perforation plates simple; intervessel pits alternate, circular to oval, non-vestured, 4-6(-8)μm; vessel-ray pits similar but half-bordered; tyloses common to infrequent.
Vasicentric or vascular tracheids absent or rare.
Fibres 1-1.4 mm long, non-septate, thin- to thick-walled, pits simple to minutely bordered.
Axial parenchyma scanty, paratracheal to vasicentric, locally aliform, in some specimens continuous tangential bands sporadically present; mostly 8 cells per parenchyma strand. Rays 6-10/mm, 300-600μm in height, homocellular to heterocellular, with one row of upright and/or square marginal cells, (1-)2-3(-4) cells wide; storied structure absent.
Crystals absent.
Silica bodies present in procumbent and upright ray cells.

Derum:.

Growth rings indistinct or absent.
Vessels diffuse, 15-35/mm², mostly in short radial multiples, 90-120μm in diameter; perforation plates simple; intervessel pits alternate, circular to oval, non-vestured, 4-6μm in diameter; vessel-ray pits similar to intervessel pits but half-bordered; tyloses, if present, not common.
Vasicentric or vascular tracheids absent or rare.
Fibres 1-1.4 mm long, non-septate, thin- to thick-walled, pits simple to minutely bordered.
Axial parenchyma banded in wide to narrow bands (generally 2-5 cells wide), bands sometimes interconnecting and forming a slightly wavy or irregular pattern; mostly 8 cells per parenchyma strand.
Rays 11-15/mm, 300-600μm in height, homocellular to heterocellular, with one row of upright and/or square marginal cells, mostly 2-3 cells wide (1-2 cells wide in some samples of C. sumatranum); storied structure absent.
Crystals absent.
Silica bodies present in procumbent and upright ray cells.

Species studied: geronggang: C. arborescens; derum: C. cochinchinense, C. formosum, C. sumatranum.

Growth and development

Little information is available on growth rates, but geronggang trees are fast growers. Mean annual diameter increments of 1.3 cm are reported in young trees. Trees are believed to reach timber size in about 60 years.

C. formosum can be easily recognized when in blossom, because the crown is then more or less leafless and the twigs appear to flush red as the buds open and subsequently carry pink flowers. Most species are heterodistylous: long-styled plants with long stamens and small pollen grains, and short-styled plants with long stamens and large pollen grains. Stamens seem not to be heteromorphic but those of the long-styled flower type curve when the flowers open, which brings the anthers to the same height as the styles of the short-styled flowers. Stigmas of long-styled plants receive much more pollen than stigmas of short-styled plants. Nectariferous petal appendages are present in heterodistylous species and the flowers are pollinated by bees (e.g. Apis spp.); these species show a trend towards specialized insect pollination. The wing-like expansion of the testa of the seed may promote dispersal by wind.

Other botanical information

The genus Cratoxylum belongs to the tribe Cratoxyleae together with two other genera from Madagascar and North America. It is most closely related to the Madagascan genus Eliea , as evidenced by features of the wood anatomy. Cratoxylum is divided into three sections. This botanical subdivision coincides with the two trade groups recognized. Geronggang wood originates from the two species of the section Isopterygium Engler which is characterized by the presence of a wing all around the seed. The two other sections (Cratoxylum and Tridesmos (Choisy) Dyer) with unilaterally winged seeds, provide derum wood.

Ecology

Geronggang characteristically occurs in freshwater or peat-swamp forest on sandy or sandy-loamy soils, and sometimes in coastal dipterocarp swamp forest. It generally appears scattered but is sometimes locally abundant and can even become dominant. Geronggang is found in areas without a pronounced dry season (A and B rainfall types) from sea-level up to 900 m, in Sabah up to 1800 m altitude. It is often found in areas with shifting cultivation or other more secondary habitats. In Sabah it is found associated with palawan (Tristania spp.) and Weinmannia blumei Planchon. In Sumatra the main associated species are pulai (Alstonia scholaris (L.) R.Br.), terentang (Campnosperma spp.) and perupok (Lophopetalum spp.).

Derum is generally found in drier sites than geronggang, such as open woodland or well-drained sites on a wide variety of soils. It occurs in both primary and secondary forests and sometimes in thickets or grassland. Derum has been encountered in heath forest and on limestone hills as well as along rivers and in hill forest from sea-level up to 1200 m altitude.

Silviculture and management

Natural regeneration of geronggang is usually scarce but is often abundant in gaps in the forest. Enrichment planting with nursery-raised seedlings on an experimental scale in Indonesia showed good results in swamp forests. Planting strips are usually spaced 6 m apart and the spacing within the strips is 2 m. Fellings may result in an increase of geronggang in swampy areas.

Harvesting

In swamp forest in Indonesia geronggang trees of over 40 cm in diameter are harvested. It is advisable to remove geronggang logs from the felling area as soon as possible; they should be sawn quickly. The logs are susceptible to fungal and insect attack and they tend to split. Geronggang logs float in water and can be transported by river. Geronggang is easy to treat with preservatives.

Genetic resources

Most geronggang and derum species occur commonly and widespread and are not readily liable to genetic erosion, but some of them (e.g. C. maingayi) are rare and may become endangered.

Prospects

Geronggang trees often occur abundantly in secondary forest (after felling), they grow rapidly, and the wood is comparatively easy to impregnate. These features extend the possibilities for this tree's application and may prove profitable in the future. However, more research is needed on growth, propagation and silviculture.

Literature

Ani Sulaiman, 1987. Malaysian timbers - geronggang. Timber Trade Leaflet No 104. Malaysian Timber Industry Board, Forest Research Institute Malaysia. 5 pp.
Ashton, P.S., 1988. Manual of the non-dipterocarp trees of Sarawak. Vol. 2. Sarawak Branch for Forest Department, Sarawak. pp. 295-302.
Browne, F.G., 1955. Forest trees of Sarawak and Brunei and their products. Government Printing Office, Kuching. pp. 195-198.
Burgess, P.F., 1966. Timbers of Sabah. Sabah Forest Records No 6. Forest Department, Sabah, Sandakan. pp. 311-316.
Gogelein, A.J.F., 1967. A revision of the genus Cratoxylum Bl. (Guttiferae). Blumea 15: 453-475.
Kochummen, K.M., 1983. Hypericaceae. In: Whitmore, T.C. (Editor): Tree flora of Malaya. 2nd edition. Vol. 2. Malayan Forest Records No 26. Longman Malaysia SDN Berhad, Kuala Lumpur. pp. 248-252.
Lim, S.C., 1985. Lesser-known timbers XIV - derum. Timber Digest 76: 1-3.
Martawijaya, A., Kartasujana, I., Kadir, K. & Prawira, S.A., 1986. Indonesian wood atlas. Vol. 1. Forest Products Research and Development Centre, Bogor. pp. 36-40.
Robson, N.K.B., 1974. Hypericaceae. In: van Steenis, C.G.G.J. (Editor): Flora Malesiana. Ser. I, Vol. 8. Martinus Nijhoff/Dr. W. Junk Publishers, The Hague, Boston, London. pp. 1-29. | 10 | Wong, C.N., 1984. Studies on Malaysian timber for plywood manufacture: preliminary trial on derum (Cratoxylon formosan). Malaysian Forester 47: 237-248.

Selection of species

Authors

J. Kartasubrata (general part),
A. Martawijaya (properties),
R.B. Miller (wood anatomy),
G. dos Santos (wood anatomy),
M.S.M. Sosef (selection of species)