4273

5(2): Timber trees; Minor commercial timbers

Homalium Jacq.

Enum. syst. pl.: 5, 24 (1760).

FLACOURTIACEAE

x = unknown; Homalium tomentosum: n = 11

Trade groups Malas: heavy hardwood, e.g. Homalium foetidum (Roxb.) Benth., Homalium longifolium Benth., Homalium tomentosum (Vent.) Benth.

Malas: aranga (En, Fr), Burma lancewood (En). Indonesia: gia (general), dlingsem (Javanese), melmas (Kalimantan), momala (Sulawesi). Malaysia: selimbar, petaling padang (Peninsular), takaliu, keruing rengkas, bansisian (Sabah). Philippines: aranga (general). Burma (Myanmar): myaukchaw, myaukugo. Laos: 'khên nang. Thailand: kha nang (central).

Homalium consists of over 200 species occurring throughout the tropics and sometimes in the subtropics. Within the Malesian area about 32 species are present. The largest number of species is found in the Philippines (11) and New Guinea (11), followed by Peninsular Malaysia (8), Borneo (5), Sumatra and Sulawesi (4), Java (3), the Moluccas (2) and the Lesser Sunda Islands (1). The two most important timber producing species, Homalium foetidum and Homalium tomentosum almost exclude each other in distribution, the first occurring in the wetter areas, the second in the drier ones.

Malas is used in general and heavy constructions, for house building (e.g. for posts, flooring, basements), posts, wharf and bridge decking, boat building (keels), oars, dunnage (as a substitute for keruing), truck bodies, scantlings, sleepers, joinery, boxes, furniture, and tool handles. It is reported as excellent for turnery. Due to its resistance to marine borers the timber is also suitable for salt water piling. It is sometimes used for charcoal and is one of the best fuelwoods in Papua New Guinea, burning even when wet.

Malas timber is exported in only limited quantities. Export is mainly from Papua New Guinea; very small amounts are available from other countries. Japan is the main importing country, others are Korea, Germany and Australia. Malas accounted in 1987 for 1.3% of the total timber import from Papua New Guinea in Japan.

Malas is a heavy hardwood. The heartwood is brown, reddish-brown or sometimes yellow-brown; sapwood slightly paler and not distinctly demarcated from the heartwood. The density of malas is (715—)750—1120 kg/m³ at 15% moisture content. The grain is straight or shallowly interlocked, sometimes deeply interlocked, texture fine and even.
At 12% moisture content the modulus of rupture of Homalium foetidum wood is c. 150 N/mm², modulus of elasticity 19 000 N/mm², compression parallel to grain 84 N/mm², shear 19 N/mm², cleavage 38 N/mm radial and Janka side hardness 9900 N.
The rates of shrinkage of malas are moderate to fairly high: from green to 12% moisture content 2.5% radial and 5.0% tangential, from green to oven dry 4.1—5.2% radial and 7.5—13.2% tangential. Malas is usually difficult to season because it is particularly prone to end and surface checking, especially back-sawn material, and it has a slight tendency to twist. However, test results from various areas differ. The wood should be quarter-sawn to avoid degrade. Air drying 4 cm thick boards from green to 15% moisture content takes about 5 months. A mild kiln schedule is recommended although some checking (sometimes severe) cannot be avoided. Checks are, however, often only shallow and can readily be removed by dressing. Kiln drying from green to 12% moisture content takes 5—6 days.
The working properties of malas are good, although the wood is slightly difficult to saw because of its high density, but it has only little blunting effect on saw teeth; it is non-siliceous. The wood planes and machines to a smooth finish with slight picking up on radial faces. It sands very well and takes a good polish, and it turns well, producing a relatively smooth finish. Pre-boring before nailing is necessary to prevent splitting. The green wood seems suitable for bent applications in furniture. It is highly suitable for the production of plywood, particulary as face veneer.
The heartwood is moderately durable to durable and is fairly resistant to termite attack. The sapwood is not susceptible to attack by Lyctus borers and ambrosia beetles. The wood of some species is resistant to marine borers. The absorption of preservatives by the heartwood is only fair, the sapwood can be treated well. In an open-tank treatment using a mixture of 50% creosote and 50% fuel oil a maximum absorption of 93 kg/m³ has been observed for heartwood of Homalium longifolium.
Freshly sawn wood has a distinct iodine-like odour that often persists through to the seasoned material. Wood of Homalium foetidum contains 59% cellulose, 35% lignin, 12% pentosan and 2.1% ash. The solubility is 11.6% in alcohol-benzene, 1.4% in cold water, 2.6% in hot water and 13.6% in a 1% NaOH solution. The energy value is about 18 150 kJ/kg.

Shrubs or small to medium-sized, rarely large, often slender trees up to 30(—62) m tall; bole generally straight and cylindrical, usually branchless for at least half the total height of the tree, up to 75(—140) cm in diameter, often with steep buttresses; bark surface smooth, corky, becoming variously rugose, rusty brown, outer bark c. 2 cm thick, inner bark hard, granular, cream with orange to yellow-brown flecks or mottles; crown comparatively narrow and dense. Leaves simple, alternate, entire or crenate-serrate, pinnately veined; stipules absent or minute and caducous. Inflorescence axillary or subterminal, many-flowered, consisting of spike-like racemes or panicles. Flowers solitary or in fascicles along the rachis, actinomorphic, bisexual, (4—)5—8(—12)-merous; calyx tube broadening upwards, connate with the ovary, with flat, linear or obovate-spatulate lobes; petals inserted in throat of calyx, similar to and alternating with the sepals; stamens positioned in front of and/or rarely on the base of the petals, solitary or in fascicles of 2—8(—12), anthers small, dorsifixed; disk consisting of usually tomentose glands opposite each sepal; ovary almost inferior, free only in the upper half, unilocular, with 2—6(—8) placentas, each with (1—)3—7 ovules near the apex, styles 2—5(—7), free or joined at base, stigma small. Fruit a capsule, dry and more or less coriaceous, often with a persistent calyx and corolla, indehiscent or splitting into 2—8 valves from the apex. Seeds 1 or few, tiny, without an aril; with abundant endosperm.

— Macroscopic characters:
Heartwood brown, reddish-brown or sometimes yellow-brown, not clearly demarcated from the paler sapwood (pale yellow-brown to pinkish-brown). Grain usually straight or sometimes interlocked. Texture fine and even; figure sometimes evident on back-sawn material from indistinct growth rings; wood dull in appearance. Growth rings usually indistinct; vessels small, indistinct to the naked eye, evenly distributed; parenchyma absent, rays not visible to the naked eye, although visible as darker streaks on quarter-sawn surfaces; ripple marks absent.
— Microscopic characters:
Vessels diffuse, (18—)24—30(—56)/mm², solitary (6—63%) and in radial multiples up to 4(—8), mostly oval, average tangential diameter 50—130(—155) µm; perforation plates simple; intervessel pits alternate, mostly polygonal sometimes rounded, non-vestured, minute, 3—4(—5) µm in diameter; vessel-ray pits half-bordered, otherwise similar to intervessel pits, often unilaterally compound; helical thickenings absent; tyloses absent. Fibres 1.1—2.1 mm long, distinctly septate, moderately thick-walled to thick-walled, with numerous indistinctly, minutely bordered pits mainly confined to the radial walls. Parenchyma absent or very sparse, paratracheal, in 2—4-celled strands. Rays 11—19/mm, uniseriate and 3—4(—5)-seriate, 0.5—1.5 mm high, markedly heterocellular, uniseriate rays composed entirely of upright cells, multiseriate rays with 4—10(—20) marginal rows of upright cells (Kribs type heterogeneous II or I); horizontal intercellular canals absent. Prismatic crystals abundant, mainly in upright ray cells, sometimes more than one crystal per chamber, strands of smaller crystals present in the septate fibres in some samples. Silica absent. Extraneous reddish-brown deposits common in ray cells of darker coloured samples.
Species studied: Homalium bracteatum, Homalium foetidum, Homalium loheri Merr., Homalium oblongifolium Merr., Homalium tomentosum.
The wood of some Nothofagus species may resemble malas, but it can easily be differentiated from malas by the presence of coarser intervessel pitting and large vessel-ray pits.

The mean heights of Homalium tomentosum trees in a plantation after 2 and 5 years are 3 m and 5 m, respectively, with a mean diameter of 7 cm at the age of 5 years. Homalium trees planted in western Java were 11 m tall after 8 years, with a diameter of 20 cm and a clear bole of 6 m.
In Java Homalium tomentosum flowers from April to September and fruits are ripe from May to September. Homalium grandiflorum flowers only every 10—15 years. The often accrescent calyx and corolla form a parachute after anthesis. Thus seed dispersal is mainly by wind.

Several of the Malesian species of Homalium were formerly placed in a separate genus called Blackwellia. In the field, species of Homalium might be confused with Euphorbiaceae, especially when the leaves are entire. Bark surface and slash characteristics are similar to those of Xanthophyllum (Polygalaceae).

Most of the species, at least the ones reaching timber size, occur in primary or sometimes secondary lowland rain forest up to 600(—1400) m altitude. They are locally common, although they do not occur gregariously, and sometimes grow in periodically inundated sites on sandy or clayey soils, sometimes on limestone, often along rivers. Homalium tomentosum occurs strictly on well-drained sites in climates with a pronounced dry season.

There are approximately 453 000 air-dried seeds of Homalium tomentosum per kg. Seeds are reported to have a very low germination capacity, less than 5%. Germination starts 3—6 weeks after sowing. Direct sowing in the field is fairly successful for this species. Plantation establishment by means of stumps or wildlings is also satisfactory. Natural regeneration is abundant and seedlings can tolerate moderate shade.

Initial growth and canopy closure of Homalium tomentosum is slow. This species is resistant to fire. It is reported to coppice well.

Locally in Irian Jaya, Homalium trees have been logged selectively and classified together with timbers from Canarium, Dillenia, Koordersiodendron, Palaquium, Syzygium and Vatica. Large trees of Homalium foetidum regularly have heart rot; the logs split easily when harvested.

Production of Homalium tomentosum is rather low, especially on poor sites. The standing stock volume of Homalium foetidum in natural forest of Papua New Guinea is estimated at 0.15—0.35 m³/ha in hill forest and 0.4—0.8 m³/ha in lowland forest. In the Bismarck Archipelago it may locally reach 6 m³/ha.

There is a risk of genetic erosion of natural populations of Homalium; moreover, very few plantations exist. In Papua New Guinea, malas is very popular and may need conservation regulations. Some species occur only very locally or are even rare, e.g. Homalium loheri and Homalium oblongifolium in the Philippines.

As the timber of Homalium is of high quality and durable, it may be worthwhile to pay more attention to problems regarding its silvicultural characteristics and the management of natural forest in which it is represented. The establishment of experimental plantations should be promoted.

Ashton, P.S., 1988. Manual of the non-dipterocarp trees of Sarawak. Vol. 2. Sarawak Branch for Forest Department Sarawak. pp. 255-258.
Bolza, E. & Kloot, N.H., 1966. The mechanical properties of 81 New Guinea timbers. Division of Forest Products Technological Paper No 41. Commonwealth Scientific and Industrial Research Organization, Melbourne. pp. 20-27.
Dahms, K.-G., 1982. Asiatische, ozeanische und australische Exporthölzer [Asiatic, Pacific and Australian export timbers]. DRW-Verlag, Stuttgart. pp. 188-189.
Desch, H.E., 1941. Manual of Malayan timbers. Vol. 1. Malayan Forest Records No 15. Federated Malay States Government. pp. 202-207.
Eddowes, P.J., 1977. Commercial timbers of Papua New Guinea. Forest Products Research Centre, Department of Primary Industry, Port Moresby. pp. 20-21.
Martawijaya, A., Kartasujana, I., Mandang, Y.I., Prawira, S.A. & Kadir, K., 1992. Indonesian wood atlas. Vol. 2. Forest Products Research and Development Centre, Bogor. pp. 46-50.
Reyes, L.J., 1938. Philippine woods. Technical Bulletin No 7. Commonwealth of the Philippines, Department of Agriculture and Commerce. Bureau of Printing, Manila. pp. 337-339.
Sleumer, H., 1954. Flacourtiaceae. In: van Steenis, C.G.G.J. (Editor): Flora Malesiana. Ser. 1, Vol. 5. Noordhoff-Kolff, Djakarta. pp. 1-106.
Sun, K.K., et al., 1983. Studies on the end-use development of lesser-known tropical timbers (II). Studies on five species amberoi (Pterocymbium beccarii K. Schum.), celtis (Celtis nymanii K. Schum.), dillenia (Dillenia papuana Martelli), malas (Homalium foetidum Benth.), spondias (Spondias dulcis Forst.), grown in Kapuluk district, New Britain, Papua New Guinea. Research Reports of the Forest Research Institute, Korea Republic No 30: 191-212.
Whitmore, T.C., 1983. Flacourtiaceae. In: Whitmore, T.C. (Editor): Tree flora of Malaya. A manual for foresters. 2nd Edition. Vol. 2. Malayan Forest Records No 26. Forest Research Institute Malaysia. Longman Malaysia SDN. Berhad, Kuala Lumpur. pp. 137-161.

E. Boer (general part), M.S.M. Sosef (general part, selection of species), W.G. Keating (properties), J. Ilic (wood anatomy)

Homalium bracteatum
Homalium caryophyllaceum
Homalium celebicum
Homalium dictyoneurum
Homalium foetidum
Homalium grandiflorum
Homalium longifolium
Homalium minahassae
Homalium panayanum
Homalium tomentosum

Boer, E., Sosef, M.S.M., Keating, W.G. & Ilic, J., 1995. Homalium Jacq.. In: Lemmens, R.H.M.J., Soerianegara, I. and Wong, W.C. (Editors): Plant Resources of South-East Asia No 5(2): Timber trees; Minor 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:
Homalium bracteatum
Homalium caryophyllaceum
Homalium celebicum
Homalium dictyoneurum
Homalium foetidum
Homalium grandiflorum
Homalium longifolium
Homalium minahassae
Homalium panayanum
Homalium tomentosum