Acer (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Acer L.

Protologue: Sp. pl. 2: 1054 (1753); Gen. pl., ed. 5: 474 (1754).

Family: Aceraceae

Chromosome number: x= 13;A. laurinum:n= 13

Vernacular names

• Maple (En, trade name)
• Indonesia: huru kapas (Sundanese), madang alu (Minangkabau, Sumatra), walik sana, wuru kembang (Javanese)
• Malaysia: perdu (Sarawak)
• Philippines: Philippine maple (En), baliag (Mountain Province), laing (Tagalog). Burma (Myanmar): Himalayan maple (En)
• Thailand: kuam.

Origin and geographic distribution

Acer comprises about 200 species occurring mainly in northern hemisphere temperate regions, particularly in North America. The only Malesian species is A. laurinum Hassk. (synonyms: A. caesium (Reinw. ex Blume) Kosterm., A. garrettii Craib, A. niveum Blume), which is found in Burma (Myanmar), Thailand, Peninsular Malaysia, Sumatra, Java, Borneo, the Philippines, Sulawesi and the Lesser Sunda Islands (east to Timor).

Uses

Utilization of the wood of A. laurinum is very limited, due to its scarcity and the absence of heartwood. It has been used for construction, especially in mountainous areas, and is suitable for boxes and crates, and walking sticks. The occasional presence of bird's-eye grain makes it suitable for fine furniture, cabinet work and musical instruments.

Production and international trade

Supplies of A. laurinum timber are very limited. The wood is used rarely and only on a local scale.

Properties

A. laurinum yields a lightweight to medium-weight hardwood with a density of 400-720 kg/m³at 15% moisture content. Heartwood pale yellow or pale brown with a pink or grey tinge, occasionally almost white, not clearly differentiated from the sapwood; grain straight to slightly interlocked; texture rather fine and even; often with conspicuous figure of coloured bands and flames, occasionally with bird's-eye grain. Growth rings very distinct due to the presence of thicker-walled fibres of a darker colour; vessels small to medium-sized, indistinct to the naked eye, solitary and in radial multiples of 2-3, open; parenchyma apotracheal in marginal or seemingly marginal bands, visible to the naked eye and prominent on longitudinal surfaces; rays visible with a hand lens, narrow and very low with pale deposits giving rise to conspicuous brownish silver grain; ripple marks absent.

The wood is moderately hard and moderately strong. It seasons well, is easy to work and finishes very well. The sapwood is susceptible to blue stain and Lyctus . The wood is non-durable when exposed to the weather or in contact with the ground.

See also the table on microscopic wood anatomy.

Botany

A deciduous to semi-evergreen, monoecious or dioecious, medium-sized to large tree up to 40(-48) m tall; bole cylindrical, branchless for up to 28 m, up to 110(-150) cm in diameter, with buttresses up to 2 m high; bark surface becoming longitudinally shallowly fissured or scaly with age, red-brown or brown to greyish-brown, middle bark brightly coloured, inner bark fibrous, mottled yellow-brown to red-brown; crown dense. Leaves decussate, simple, entire, whitish or pale blue-grey and with prominent reticulation below, exstipulate. Flowers in a unisexual, axillary, corymbose panicle, small, regular, pale yellowish; sepals and petals 4-5; stamens (4-)6(-8); disk present; ovary superior, 2-locular, woolly, with 2 ovules in each cell, styles 2. Fruit a red or purplish samara which splits into 2(-3), winged, 1-seeded parts. Seedling with either epigeal or hypogeal germination; leaves coarsely, distantly toothed.

Trees have been observed flowering in April to August and are generally leafless when in flower. Pollination is by bees which collect the honey. Ripe fruits are present from July to November, but in Sabah trees are reported to set fruit rarely. The winged fruits are dispersed by wind.

Acer is the only genus of the family Aceraceae found in the Malesian area. A. laurinum belongs to the monotypic section Hyptiocarpa Fang. A. garrettii Craib has long been considered to comprise a distinct species but fairly recently it proved to be identical with A. laurinum .

Ecology

A. laurinum occurs scattered in primary, or occasionally secondary, hill or montane forest, at (150-)800-2550 m altitude. It grows in seasonal to non-seasonal climates.

Silviculture A. laurinum can be propagated by seed: per kg there are about 4900 dry, winged fruits. It may be planted at 1000-1500 m altitude, but planting on open sites is not recommended. Conversion of the wood should be done rapidly after harvest to avoid serious discolouration from moulds and sap-stain fungi.

Genetic resources and breeding

A. laurinum is uncommon but fairly widespread and seldom harvested and does not seem to be threatened. There are no records of ex situ conservation.

Prospects

As the quality of the wood is not very high, the utilization of A. laurinum will probably not increase in the near future. It may prove useful for small objects like household utensils and picture frames. A. laurinum has some ornamental value because of its conspicuous glaucous lower leaf surfaces.

Literature

61, 70, 101, 198, 232, 238, 257, 260, 267, 341, 436, 595, 617, 772, 780, 861, 934, 974, 976, 1048, 1125, 1137, 1221.

R.E. Nasution