Afzelia (PROSEA)

Plant Resources of South-East Asia
Introduction

Afzelia J.E. Smith

Protologue: Trans. Linn. Soc., London 4: 221 (1798).

Family: Leguminosae

Chromosome number: x= unknown; n= 12 reported for several non-Malesian species

Trade groups

Afzelia: heavy hardwood, Afzelia javanica (Miq.) J. Léonard, A. rhomboidea (Blanco) S. Vidal, A. xylocarpa (Kurz) Craib.

Vernacular names

Afzelia (En)
Philippines: tindalo (Tagalog), balayong (central), apalit (Luzon)
Cambodia: beng
Laos: kha
Thailand: makha-mong (general), makha-luang (northern), makha-yai (central)
Vietnam: gõ.

Origin and geographic distribution

Afzelia consists of some 15 species, most (about 10) of which are African. Three species occur in the Malesian region and are confined to eastern Sumatra, western Java, western and northern Borneo and the Philippines. A. rhomboidea is the most widespread Malesian species. One species is native to mainland South-East Asia (Burma, Indo-China, Thailand).

Uses

Afzelia wood is highly valued; it is nicely figured and durable. It is regarded as one of the finest woods for high grade furniture, cabinet work, parquet flooring and interior finish. It is also used for house construction, mainly as door and window frames but also for beams, panelling, doors and stairs. Other general uses are wood handicrafts, musical instruments, agricultural tools, boats, waterwheels, carts and sleepers. A decorative veneer can be made from the wood, but the wood is often regarded as too hard and dense for making utility plywood.

The bark of A. xylocarpa is used for tanning cattle hides and goat and sheep skins. The fatty cotyledons of young seeds are edible.

Production and international trade

The production of wood from A. xylocarpa in Thailand was 25 000 m³ in 1985, 28 000 m³in 1986, 40 000 m³ in 1987, and 34 000 m³ in 1988. The wood is mostly used domestically to produce furniture and parquetry. The average price of sawn Afzelia timber in Thailand was US$ 430/m³ in 1985 and 1986, increasing to US$ 715/m³ in 1988. Production and trade figures are not available from other countries. Afzelia timber is not important in the trade in South-East Asia except for Thailand, although A. rhomboidea wood is highly valued in the Philippines for furniture and interior finishing. There is probably still some trade in the Philippines.

Properties

Afzelia wood is heavy and hard. The heartwood is reddish-yellow, red to dirty red-brown, often with some streaks, and distinctly demarcated from the grey-white sapwood. The density is 850-900 kg/m³ at 15% moisture content. The grain is interlocked or sometimes straight (e.g. A. javanica), texture moderately fine to moderately coarse. Planed surfaces are often glossy.

For A. xylocarpa at 15% moisture content, the modulus of rupture is 95-125 N/mm², compression parallel to grain 53-65 N/mm² and shear about 17 N/mm². For A. rhomboidea at green condition (about 50% moisture content), the modulus of rupture is 84 N/mm², modulus of elasticity 11 000 N/mm², compression parallel to grain 33 N/mm², compression perpendicular to grain 12 N/mm², shear 12 N/mm², Janka side hardness 7635 N and Janka end hardness 7135 N.

The wood seasons well with little shrinkage and warping. It is moderately difficult to work, but easy in comparison with other high-density woods. The wood takes a high finish. It is very durable; the durability under exposure is about 10 years in tropical conditions.

The bark of A. xylocarpa contains catechol and pyrogallol; these chemical substances have tanning properties.

Description

Medium-sized trees of up to 42 m tall; bole straight or twisted, branchless for up to 15(-20) m, up to 120(-180) cm in diameter, buttressed or not, or fluted; bark thin, smooth, grey, sometimes with brown or black spots, inner bark white to brown or red; crown often broad and sprawling.
Leaves alternate, paripinnate with 3-9 leaflets; stipules very small and early caducous; leaflets opposite, leathery and usually glabrous. Inflorescence paniculate, terminal or lateral with puberulous peduncles.
Flowers bisexual, rather large, with bracteoles shorter than the flower buds; receptacle elongate; sepals 4, imbricate, puberulous on the outer side; petal 1, orbicular or kidney-shaped with a long claw; fertile stamens usually 7, free or fused in the basal half, staminodes 2-4, rarely absent; ovary stipitate, with the stipe adnate to the tubular receptacle, with many uniseriate ovules, style elongate with a small dark stigma.
Pod compressed, woody, glabrous, dark brown or black at maturity.
Seed elliptical to orbicular, rather thick, with a prominent yellow to red aril.
Seedling with epigeal germination; cotyledons succulent, hardly spreading; first two leaves opposite, subsequent leaves arranged spirally, first leaves often with somewhat larger leaflets.

Wood anatomy

Macroscopic characters

Heartwood dirty red-brown, distinctly demarcated from the grey-white sapwood. Grain straight. Texture moderately coarse. Growth rings usually distinct because vessels are absent in the inner part of a growth ring; in the remaining part, vessel diameter decreasing from inner to outer side; vessels just visible to the naked eye, in heartwood locally filled with a homogeneous red-brown mass; vasicentric parenchyma distinct, rays only visible with a lens; ripple marks absent.

Microscopic characters

Growth rings boundaries marked by initial parenchyma and/or by a difference in vessel frequency. Vessels diffuse, usually absent in the inner part of a growth ring, 3-8/mm², solitary and in radial multiples of 2-4, solitary vessels often arranged in zones separated from zones with predominantly radial pore multiples, completely surrounded by parenchyma, round to oval, average tangential diameter 110-190μm; perforations simple; intervessel pits alternate, distinctly vestured, hexagonal, 6μm, often with coalescent apertures; vessel-ray pits numerous, vessel-axial parenchyma pits scarce to very numerous, both similar to intervessel pits but half-bordered. Fibres 450-675μm long, non-septate, thick-walled, with simple pits confined to the radial walls; gelatinous layers often present, almost entirely filling up the fibre lumina. Axial parenchyma abundant, mainly paratracheal but also banded and apotracheal; paratracheal parenchyma vasicentric to winged-aliform, often developing into banded parenchyma; banded parenchyma present except in the inner part of a growth ring where vessels are often absent, 1-4 cells wide, some bands long in tangential direction, also initial; apotracheal diffuse parenchyma scarce, usually near paratracheal and banded parenchyma; parenchyma strands (2-)4-celled. Rays 6-10/mm, (1-)2-3(-4)-seriate, up to 5-25 cells high, homocellular, entirely composed of procumbent cells. Crystals prismatic, in chambered axial parenchyma cells. Deposits present in heartwood; vessels locally with red-brown gummy contents, also libriform fibres, axial and ray parenchyma often entirely or partly filled up with red-brown solid deposits or with colourless to red-brown grains. All elements non-storied.

Species studied: A. javanica.

Growth and development

Four-month-old seedlings of A. xylocarpa are 30-35 cm high; after 3 years they are 135 cm tall on average. As expected from the dense wood, Afzelia trees are slow growers. Mean annual girth increment is unknown.

A. javanica flowers in Java from October to November, A. rhomboidea in the Philippines from August to September. Fruits of A. xylocarpa in Thailand are fully mature in June to August.

Other botanical information

The genus Afzelia is closely related to Intsia, differing only in the number of fertile stamens, the thicker and more woody pod and the arillate seed. The wood of Afzelia and Intsia is fairly similar. The Asian species were formerly placed within a separate genus, Pahudia, because they differ from the African species in having partly fused filaments. This feature has, however, been proved to be variable and consequently Pahudia has been united with Afzelia. Afzelia J.E. Smith is conserved against the older homonym Afzelia J.F. Gmelin, a genus of the Scrophulariaceae.

Ecology

Afzelia occurs scattered in mixed deciduous and dry evergreen forests, usually on well-drained clayey or laterite soils but sometimes in periodically inundated places. It is found at low altitudes, up to 400 m within Malesia, but up to 900 m on the South-East Asian mainland. In Java, A. javanica is locally planted up to 800 m altitude. In the Philippines, tindalo (A. rhomboidea) is found on low ridges and hills near the coast and along the edges of dipterocarp forests.

Propagation and planting

In Thailand, pods of A. xylocarpa are collected when they become brown or dark brown and before they split open. After air drying for one week, the pods are opened to retrieve the seeds, which are then cleaned. The seed weight of A. xylocarpa is 6.5-8 g on average. Before sowing, the aril is removed and the seeds are soaked in water for 24-72 hours. Soaking for one hour in a 20% solution of sulphuric acid promotes germination. The seeds are then sown in nursery beds or in pots filled with compost. The beds must be shaded (with a light reduction of 50%) and watered occasionally. Usually the seeds germinate in 1-2 weeks. Seedlings are often transplanted into containers filled with a mixture of black ash (25%), coarse sand (12.5%), green manure (12.5%) and garden soil (50%). They are planted into the field when about 35 cm tall, generally at 4 m × 4 m.

Silviculture and management

Afzelia wood is usually obtained from natural forests which are managed under selective cutting systems. In Thailand, trees were formerly cut selectively in a 15-30-year-rotation. At present the minimum girth of the bole permitted for cutting is 200 cm at breast height (about 64 cm in diameter). Only a few plantations of Afzelia exist. In Thailand, A. xylocarpa is planted in mixed plantations, together with rosewood (Dalbergia spp.) and teak (Tectona grandis L.f.). In Java, A. javanica is planted very locally.

Diseases and pests

Seedlings of A. xylocarpa in nurseries often suffer from damping-off, a disease caused by fungi such as Phytophthora, Pythium, Fusarium and Rhizoctonia spp. Seedlings are also attacked by larvae of insects such as longhorn beetles of the genera Aristobia and Batocera, but these pests are less serious in mixed plantations.

Harvesting

As the branchless bole of Afzelia trees is usually not long and the wood is heavy, the logs prepared for transportation are usually short. The logs sink in water and must be transported over land. To prevent insect attack, the logs are debarked soon after cutting, and to prevent splitting they are coated at both ends with tar or lime.

Genetic resources

Usually Afzelia trees occur scattered in the forest. As the timber is regarded locally as very valuable (e.g. in Thailand and the Philippines) the desire to cut the trees is great, and in the past exploitation has been considerable, at least locally. This makes the species liable to genetic erosion.

Prospects

Afzelia yields a timber that can be used for many purposes. The supply is, however, limited. Planting is carried out on a very small scale. The establishment of mixed plantations seems promising, but more information on growth, propagation and silviculture is needed, in particular for the species occurring outside Thailand, about which almost nothing is known.

Literature

Chalermpongse, A., 1982. Damping-off of seedlings in forest nurseries. Technical Bulletin No 725. Royal Forest Department, Bangkok. 19 pp.
Cockburn, P.F., 1976. Trees of Sabah. Vol. 1. Forest Department Sabah, Kuching. pp. 157-158.
Dahms, K.-G., 1982. Asiatische, Ozeanische und Australische Exporthölzer [Asiatic, Pacific and Australian export woods]. DRW-Verlag, Stuttgart. pp. 187-188.
de Guzman, E.D., Umali, R.M. & Sotalbo, E.D., 1986. Guide to Philippine flora and fauna. Vol. 3. Dipterocarps, non-dipterocarps. Natural Resources Management Center, Ministry of Natural Resources and University of the Philippines, Manila. pp. 199-200.
de Vogel, E.F., 1980. Seedlings of dicotyledons. Pudoc, Wageningen. pp. 306-308.
Larsen, K., Larsen, S.S. & Vidal, J.E., 1984. Leguminosae - Caesalpinioideae. In: Smitinand, T. & Larsen, K. (Editors): Flora of Thailand. Vol. 4. TISTR Press, Bangkok. pp. 126-128.
Reyes, L.J., 1938. Philippine woods. Technical Bulletin No 7. Commonwealth of the Philippines, Department of Agriculture and Commerce, Manila. pp. 137-139.
Royal Forest Department, 1985. The Thai hardwoods. Technical Bulletin No R.188. 127 pp.
Santisuk, T. & Niyomdham, C., 1983. Leguminosae. In: Phengklai, C. (Editor): Thai economic trees. Part 3. ACFT Press, Bangkok. pp. 199-201.
Switachart, S., 1972. A study on seed germination of makha mong (Afzelia xylocarpa) by soaking in different concentrations of sulphuric acid. Technical Bulletin No R.138. Royal Forest Department, Thailand. pp. 5-10.

Selection of species

Authors

C. Phengklai (general part),
T. Smitinand (general part),
R.P. van der Zwan (properties),
R.W. den Outer (wood anatomy),
M.S.M. Sosef (selection of species)