Alphitonia (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Alphitonia Reissek ex Endl.

Protologue: Gen. pl.: 1098 (1840).

Family: Rhamnaceae

Chromosome number: x= unknown; 2n= unknown

Vernacular names

• Papua New Guinea: white almond (En).

Origin and geographic distribution

Alphitonia comprises about 10 species occurring in Borneo, the Philippines, the Lesser Sunda Islands (Timor), the Moluccas, New Guinea, Australia and in the Pacific east to the Marquesas Islands and Hawaii. Only 2 species occur in Malesia.

Uses

The wood of Alphitonia is used for temporary construction, house building (posts, rafters), interior finish, cabinet making, furniture, mouldings, turnery, veneer, joinery, flooring, vehicle bodies, barrels, fencing and axe handles. It yields a good firewood and is suitable for the production of pulp.

The bark of A. excelsa has been used for rope in the Philippines and as soap in the Moluccas. It has also been used in tanning. Its wood has been used to dye cloth red-brown or orange-yellow. In Australia the leaves are used as fodder. In Papua New Guinea Alphitonia is regarded as suitable for reforestation purposes.

Production and international trade

Alphitonia wood is used mainly on a local scale. In 1996 Papua New Guinea exported 515 m³of "white almond" logs at an average free-on-board (FOB) price of US$ 95/m³.

Properties

A. macrocarpa yields a lightweight to medium-weight hardwood with a density of 360-650 kg/m³at 12% moisture content, A. excelsa is a medium-weight to occasionally heavy timber with a density of 685 to over 830 kg/m³. Heartwood pink-brown, sapwood straw-coloured; wood occasionally streaky and always with a smell of "sarsaparilla" ( Smilax spp.). Growth rings indistinct; vessels small to medium-sized, solitary and in radial multiples of 2-4 occasionally over 4, with dark gummy and white deposits; parenchyma sparse, paratracheal vasicentric or apotracheal in irregularly spaced bands; rays moderately fine; ripple marks absent.

Shrinkage upon air drying is moderate. The wood of A. macrocarpa is weak and non-durable but that of A. excelsa is strong and moderately durable. The sapwood is non-susceptible to Lyctus .

The bark of A. excelsa shows antibacterial activity. The average fibre length of A. excelsa wood is 1.04 mm and it is suitable for chemical pulping having a high pulp yield and requiring comparatively few chemicals.

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

Botany

Evergreen, small to fairly large trees up to 40 m tall; bole straight, up to 100 cm in diameter, branchless for up to 20 m, without buttresses; bark surface smooth, greyish to whitish or greenish-brown, pustular, inner bark greenish or straw-coloured with spicy odour. Buds and young twigs often densely brownish pubescent. Leaves alternate, simple, entire, whitish or rusty pubescent below; stipules small, caducous. Inflorescence an axillary or rarely terminal, many-flowered cyme. Flowers bisexual, small, whitish to greenish, 5-merous; hypanthium saucer-shaped to hemispherical; sepals keeled within; petals clawed, hooded; disk thick, nectariferous; ovary inferior, 2-3-locular with 1 ovule in each cell, style short, 2-3-lobed. Fruit a globose to broadly ovoid drupe with 2-3 dehiscent stones; mesocarp thick, mealy. Seed almost completely enclosed in a loose, membranous, reddish-brown aril; testa smooth.

A. excelsa develops according to Roux's architectural tree model, characterized by a continuously growing monopodial orthotropic trunk with plagiotropic branches. In the Philippines A. excelsa is considered a fast-growing species. Seeds are eaten and dispersed by birds.

Ecology

Alphitonia is a fairly common element of lowland to montane, disturbed or secondary rain forest, up to 2500 m altitude. In Papua New Guinea A. excelsa can be found in the dry savanna belt in the south-east; in Australia it is reported to grow sometimes on very poor sandy soils. A. macrocarpa is found in the montane regions of Papua New Guinea, especially in secondary forest and in fallow vegetation.

Silviculture Alphitonia is reputed to have pioneer characteristics.

Genetic resources and breeding

As harvesting of Alphitonia timber is limited, genetic erosion is not a major risk.

Prospects

It is unlikely that the use of Alphitonia timber, at least in South-East Asia, will increase in the near future, due to its relatively sparse occurrence.

Literature

46, 135, 150, 163, 304, 348, 355, 402, 436, 447, 464, 553, 568, 739, 955, 974, 1048, 1070, 1090, 1222, 1232.