Macaranga (PROSEA Timbers)

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Plant Resources of South-East Asia
Introduction
List of species


Macaranga Thouars

Protologue: Gen. Nov. Madag.: 26 (1806).
Family: Euphorbiaceae
Chromosome number: x= 11; M. denticulata (Blume) Müll. Arg., M. indica, M. peltata (Roxb.) Müll. Arg., M. tanarius: n= 11

Vernacular names

  • Mahang (trade name). Macaranga (En)
  • Brunei: marakubong, sedaman
  • Indonesia: mahang kapur (general)
  • Malaysia: benua (Sarawak), marakubong (Sabah)
  • Papua New Guinea: macaranga (En)
  • Philippines: hamindang (Filipino)
  • Burma (Myanmar): petwaing
  • Thailand: lo.

Origin and geographic distribution

Macaranga comprises some 250 species. About 30 of these occur in tropical Africa and Madagascar, the rest in tropical Asia from India to Indo-China, China, Taiwan, the Ryukyu Islands, Thailand, throughout the Malesian region, northern Australia and the Pacific, east to Fiji. The main centre of diversity is found within Malesia where some 160 species occur, with an exceptionally high number of endemics in Borneo and New Guinea.

Uses

Peeled Macaranga poles are frequently used for temporary construction and especially for parts of native houses not in contact with the ground. The wood is used for light framing, interior trim, moulding, shingles, packing cases, outriggers for canoes and, especially, match splints. In the Philippines it has been a favourite wood for wooden shoes. M. indica has been used to support pepper vines. Poles of M. tanarius have been used by pepper growers in southern Sumatra to make temporary ladders to harvest their crop. Macaranga yields a high-quality pulp and produces high-quality particle board, cement-bonded board and wood-wool board, and is suitable for the production of plywood. It provides good fuelwood.

The bark and pith or the fruit of several species produce a resin or gum called "kino" or "selaru" that can be used as a glue. The bark of some species has been used to tan fishing nets and in Papua New Guinea as twine for hut construction. Certain species are the most common hosts of the lac insect; production, however, is negligible. A decoction of the leaves or roots of various species is used as an internal medicine. In Malaysia a decoction of the root-bark of various species is drunk to treat diarrhoea, dysentery, fever, used to clean wounds and applied after childbirth. Large leaves of M. gigantea and M. mappa are used to wrap food, etc.

Production and international trade

Macaranga is regarded as a commercial timber in Indonesia, but little is traded separately. When traded it is found in mixed consignments of lightweight hardwood. In 1996 Papua New Guinea exported 219 m3of Macaranga logs at an average free-on-board (FOB) price of US$ 98/m3.

Properties

Macaranga yields a lightweight hardwood with a density of 270-500(-590) kg/m3at 15% moisture content, but for M. involucrata densities of over 830 kg/m3and for M. lowii of 800-815 kg/m3are reported. Heartwood pale yellow-brown to pale brown or grey-brown, sometimes with a pinkish tinge, not clearly differentiated from the sapwood; grain straight or slightly interlocked; texture moderately fine to moderately coarse and even; planed surfaces lustrous. Growth rings sometimes apparent; vessels moderately small to medium-sized, solitary and in radial multiples of 2-4(-6), tyloses few; parenchyma moderately abundant, apotracheal in narrow bands, visible with a hand lens, occasionally tending to diffuse or diffuse-in-aggregates; rays very fine, visible with a hand lens; ripple marks absent.

Shrinkage is moderate and in seasoning the wood is liable to sap-stain and is subject to insect attack. The wood is soft to moderately hard and fairly weak. It is very easy to work but somewhat fibrous. The wood is non-durable and permeable to pressure treatment. It is moderately resistant to susceptible to dry-wood termites, the sapwood is susceptible to Lyctus .

The medicinal properties are probably due to the tannin.

See also the tables on microscopic wood anatomy and wood properties.

Botany

Evergreen, dioecious, small to medium-sized trees up to 30(-40) m tall; bole straight, up to 50(-70) cm in diameter, occasionally with stilt roots, rarely with buttresses; bark surface smooth or rough with lenticels, hoop-marked, stripping off easily, greyish or pinkish, inner bark pink to reddish-brown, sometimes exuding a colourless, pink or red-brown gum; crown open, often bluish-green. Leaves arranged spirally, simple, palmately or pinnately veined, the main veins joined by parallel, concentric veinlets giving the effect of spider-webbing, often prominently lobed, sometimes peltate; petiole often long and kneed; stipules often large and persistent. Flowers small, in a short, lateral raceme of small clusters subtended by often glandular bracteoles; petals absent; disk absent. Male flower with 2-5-lobed calyx, lobes valvate; stamens 1-20; anthers 3-4-celled; pistillode absent. Female flower with 3-5-lobed calyx; ovary superior, (1-)2-3(-6)-locular with 1 ovule in each cell, styles usually free and unlobed. Fruit a leathery or woody, often shouldered capsule, smooth to variously spiny, splitting into 2-valved parts leaving the central, commonly waxy column. Seed black, often with a thin orange to red aril. Seedling with epigeal germination; cotyledons emergent, leafy; hypocotyl elongated; all leaves arranged spirally, conduplicate to involute.

Macaranga species are short-lived pioneers becoming 15-20 years old. Most species develop according to Rauh's architectural model, characterized by a monopodial trunk with rhythmic growth and so developing tiers of branches that are themselves morphogenetically identical with the trunk. M. conifera , however, develops according to the Koriba's architectural model which is characterized by orthotropic axes which branch to produce initially equivalent modules but subsequently one of these becomes dominant constituting one unit of the sympodial trunk. Trees may flower when very young. Flowering and fruiting are fairly regular, several times a year. A few Macaranga species are either facultative or obligate myrmecophytes. The latter group of species provides specific nesting space, mainly hollow twigs, for ants of the genus Crematogaster . The ants protect the plants from herbivores.

The dimorphism of sapling leaves and those of mature trees renders identification difficult. Macaranga is very closely related to Mallotus , but differs in its 3-4-celled anthers and more conspicuously in its lateral inflorescences and the absence of stellate hairs.

Ecology

Most Macaranga species are pioneers and form a characteristic element of secondary forest especially along roadsides in western Malesia and New Guinea, but are less common in Sulawesi, the Moluccas and Java. They are often found gregariously and may locally form pure stands. A few species (section Pseudorottlera (Rchb. f. & Zoll.) Pax & K. Hoffm.) are found in primary forest. Most species thrive in a perhumid climate, some also under slightly seasonal conditions. The altitudinal range is large, with a few species occurring up to almost 3000 m altitude in New Guinea. Some species may occur along rivers and streams, in secondary seasonal swamp forest (e.g. M. recurvata ), secondary peat-swamp forest (e.g. M. pruinosa ), and on a wide variety of soil types including sandy, tufa, and clayey soils and limestone.

Silviculture Macaranga can be propagated by seed. For M. tanarius there are about 54 500 dry seeds/kg. Seeds of M. tanarius sown with adhering pulp have about 50% germination in 24-72(-265) days, whereas those of M. triloba have about 80% germination in 19-37 days. It is, however, difficult to get seedlings to grow. Most of the trees are very fast-growing pioneers but as they are small and low-branching, they are not interesting for the production of sawn timber. M. tanarius has been suggested as a shade and shelter tree to promote natural regeneration on deforested land. A few species reach 50 cm in diameter, e.g. M. hypoleuca .

Genetic resources and breeding

Some species are narrow endemics, but the genetic resources of most Macaranga species are not in danger as trees are common and characteristic elements of secondary vegetation.

Prospects

The fairly general occurrence of Macaranga and the long wood fibres make the exploitation for pulp and paper and the production of wood-based panels promising in the near future.

Literature

26, 33, 36, 70, 82, 83, 151, 162, 163, 209, 260, 267, 300, 337, 348, 402, 405, 428, 429, 436, 526, 543, 565, 678, 740, 741, 745, 780, 829, 831, 861, 934, 955, 966, 974, 1038, 1169, 1195, 1211, 1215, 1216, 1217, 1218, 1221, 1239, 1242, 1251.