Alloxylon (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Alloxylon P.H. Weston & Crisp

Protologue: Telopea 4: 498 (1991).

Family: Proteaceae

Chromosome number: x= unknown;A. flammeumP.H. Weston & Crisp: 2n= 22

Vernacular names

• Pink silky oak (En, trade name)
• Indonesia: kawoli (Je, Merauke, Irian Jaya).

Origin and geographic distribution

Alloxylon comprises 4 species, 3 of which are endemic to Australia. The only Malesian species is A. brachycarpum (Sleumer) P.H. Weston & Crisp (synonyms: Embothrium brachycarpum Sleumer, Oreocallis brachycarpa (Sleumer) Sleumer) which occurs in the southern Moluccas (Aru Islands) and southern New Guinea.

Uses

The nicely figured and attractive wood of A. brachycarpum is used for boat-building, interior trim, fine finish, furniture and cabinet work, mouldings, decorative wall panelling, inlaying and marquetry, turning and fancy veneer.

A. brachycarpum is a potential ornamental plant.

Production and international trade

In 1996 Papua New Guinea exported only 121 m³of "pink silky oak" logs at an average free-on-board (FOB) price of US$ 99/m³. Supplies are very limited.

Properties

A. brachycarpum yields a medium-weight hardwood with an average density of 540 kg/m³at 12% moisture content, but has also been reported to yield a lightweight wood of about 400 kg/m³. Heartwood pale pinkish-brown to deep pink, sapwood pale pink or pale yellow-brown; grain straight; texture medium to moderately coarse, uneven due to the broad rays; wood nicely figured with conspicuous silver grain and silky lustre on tangential surface. Growth rings indistinct; vessels moderately large, solitary and occasionally in radial multiples of up to 4, in tangential multiples and in clusters tending to tangential arrangement, visible to the naked eye, with pink deposits; parenchyma paratracheal vasicentric, aliform and confluent with narrow bands; rays of two distinct sizes, as wide as or wider than the vessels, conspicuous on radial surface; ripple marks absent.

Shrinkage upon seasoning is low and the wood seasons readily with very little degrade. The wood is fairly weak and moderately soft. It works excellently with both hand and machine tools and peels and slices well. It planes to a smooth surface and takes an excellent polish. The wood is moderately durable and extremely resistant to impregnation. The sapwood is susceptible to Lyctus .

See also the table on microscopic wood anatomy.

Botany

A medium-sized to large tree up to 40 m tall; bole straight, cylindrical, up to 85 cm in diameter, sometimes slightly spurred at base; bark surface shallowly fissured, pustular, peeling off in thick scales, brown to greyish, inner bark wine-red; crown small, open. Leaves arranged spirally, simple, entire, decurrent at base, exstipulate. Inflorescence an axillary raceme, (2-)10-50-flowered, 1-sided. Flowers in pairs, zygomorphic; tepals connate in a long, straight, cylindrical tube which splits into 4 segments, pinkish-red to bright red; stamens sessile, inserted near the apex of the tepals; disk semi-annular; ovary superior, long stipitate, fusiform, 1-locular with many ovules in 2 rows, style long, apically thickened. Fruit an oblong follicle, splitting at one side, with 2 rows of 5-7 seeds. Seed with a large distal wing. Seedling with epigeal germination; cotyledons fleshy; seedling leaves simple, entire.

A. brachycarpum is probably pollinated by birds. Its flowering period is from June to October. Fruits have been observed in July-September and January-February. The winged seeds are dispersed by wind.

Ecology

A. brachycarpum occurs scattered but is locally common in well-drained, primary, mixed rain forest on hills, ridges and high river banks, up to 800 m altitude. It seems to prefer gallery forest but has also been found in bamboo-eucalypt forest. It is often found growing together with Acacia , Flindersia and Grevillea spp.

Genetic resources and breeding

A. brachycarpum has a small area of distribution and is probably vulnerable to genetic erosion by habitat destruction.

Prospects

The use of Alloxylon wood is unlikely to increase, because supplies are very limited. However, this highly decorative wood will remain in demand.

Literature

300, 304, 341, 348, 403, 423, 464, 1024, 1200, 1232.

E. Boer & M.S.M. Sosef