Albizia (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Albizia Durazz.

Protologue: Mag. Tosc. 3: 11 (1772).

Family: Leguminosae

Chromosome number: x= 13; A. chinensis, A. lebbeck, A. lebbekoides, A. procera: 2n= 26

Vernacular names

• Albizia (En)
• Malaysia: batai, batai batu, kungkur (general).

Origin and geographic distribution

Albizia comprises about 150 species and has a pantropical distribution, with centres of speciation in Africa, Madagascar and tropical America. It occurs throughout the Asian tropics and 20 species are indigenous within the Malesian region. A. lebbeck is planted and naturalized throughout the tropics.

Uses

In South-East Asia the wood of Albizia is quite variable in quality and is used for house construction (posts, beams), bridge construction, mine timber, boat building, dugout canoes, spokes and wheel rims, furniture and cabinet work, framework, mouldings, shuttering, interior finish, parquet and strip flooring, panelling, partitioning, oars, casks, oil presses, agricultural implements, carving, musical instruments, picture frames, turnery, gunstocks, novelties, fancy boxes, matches and matchboxes. The wood is suitable for the production of veneer and plywood, sometimes even for decorative veneers, and produces good firewood and charcoal. In the Philippines A. acle is regarded a suitable substitute for black walnut ( Juglans nigra L.) from the temperate zones.

Albizia is frequently planted as a shade tree for various crops like tea and coffee and to improve the soil fertility, occasionally as an ornamental in parks and along roads. A. chinensis , A. lebbeck and A. procera are also planted to rehabilitate degraded sites and in fire- and wind-breaks. The trunk of A. lebbeck and A. procera yields a gum which is similar to arabic gum. A red dye and tannin used to be extracted from the bark, especially that of A. lebbekoides . The bark of the latter is used in Cambodia as a remedy for colic, and in the Philippines it is put into fermenting sugar cane juice to make an intoxicating liquor. The bark, which contains saponin, has been used as a substitute for soap (especially A. saponaria ), as a fish poison, and shows insecticidal activity. Leaves of some species are sometimes used as fodder for cattle. The outer bark of A. splendens is used for lighting fires in humid conditions.

Production and international trade

In Sabah the lightweight wood of A. chinensis and A. pedicellata is traded as "batai" together with the wood of Paraserianthes falcataria (L.) I.C. Nielsen, the medium-weight timber as "batai batu". In 1992 "kungkur" timber ( A. splendens ) was exported from Sabah together with "petai" ( Parkia spp.), as a total volume of 2100 m³of sawn timber and a total value of about US$ 480 000. In 1996 Papua New Guinea exported about 11 810 m³of "brown albizia" ( A. procera ) logs at an average free-on-board (FOB) price of US$ 99/m³.

Properties

Albizia yields a lightweight to medium-weight, occasionally heavy hardwood with a density of 315-950 kg/m³at 15% moisture content. Important species and their density at 15% moisture content are: A. pedicellata 315-450 kg/m³, A. chinensis 320-640 kg/m³, A. splendens 470-845 kg/m³, A. lebbekoides 500-900 kg/m³and A. procera 600-950 kg/m³. Heartwood pale brown to dark reddish-brown or golden-brown with paler streaks and bands, often similar to Juglans spp., sharply demarcated from the white to straw-coloured sometimes very wide sapwood; grain sometimes straight but usually interlocked or wavy; texture moderately fine to moderately coarse and even. Maximum sapwood width of 12-15-year-old trees is 10-12 cm. Growth rings sometimes distinct due to contrast in density of the fibres between earlywood and latewood; vessels medium-sized to very large, solitary and in radial multiples of 2-3(-4) with a tendency to oblique arrangement, vessels with white, yellow or dark gum-like or solid deposits; parenchyma moderately abundant, apotracheal diffuse and paratracheal vasicentric and aliform, sometimes confluent, also apotracheal in marginal bands; rays very fine to moderately fine; ripple marks absent; pith flecks occasionally present.

Shrinkage is low to moderate or high, but the wood seasons well with little or no degrade, although logs of some species are liable to develop heart shakes unless converted green. Boards of A. splendens 13 mm and 38 mm thick take respectively 3.5 and 4.5 months to air dry. Kiln drying gives good results. The wood is soft and fairly weak (lightweight species), or moderately hard and strong (medium-weight species); that of A. procera is reported hard, strong and tough. The wood is somewhat difficult to work with hand and machine tools and tends to pick up in planing and moulding; the cutting angle should not exceed 20. The wood of A. splendens , however, has good working properties and finishes well, both in the green as well as in the air-dry state. It polishes excellently. The wood is non-durable to durable when in contact with the ground or exposed to the weather. In a graveyard test in the Philippines the average service life was 10 years for A. acle and A. procera , 3 years for A. saponaria and only 16 months for A. chinensis . The wood is resistant to dry-wood termites but the sapwood is susceptible to Lyctus . The heartwood is extremely resistant to impregnation, the sapwood is permeable. The energy value of the wood is 19 500-21 500 kJ/kg.

Sawdust may cause irritation to mucous membranes. The bark of older trees of A. lebbekoides contains 15-20% tannin.

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

Botany

• Evergreen to briefly deciduous shrubs or small to fairly large trees up to 35(-50) m tall, rarely armed lianas; bole straight or rather crooked, short or branchless for up to 20 m, up to 100(-150) cm in diameter, sometimes with small buttresses; bark surface smooth to closely fissured, lenticellate, grey to blackish, inner bark coarsely fibrous, reddish-brown or yellow to cream; crown usually flattened.
• Leaves arranged spirally, bipinnate, rachis and pinnae with extrafloral nectaries; leaflets many, opposite, entire; stipules caducous.
• Flowers in pedunculate glomerules or corymbs which are axillary or aggregated into a terminal or axillary panicle, 5-merous, often dimorphic, the marginal flowers in each head bisexual, the central ones male; calyx and corolla connate, valvate; stamens many, united into a tube below, long exserted; ovary superior, 1-locular with many ovules, style filiform.
• Fruit a straight, flat, dehiscent to indehiscent pod.
• Seed circular to ellipsoid, more or less flattened, the hard testa with pleurogram.
• Seedling with epigeal germination; cotyledons emergent, fleshy; hypocotyl elongated; first 2 leaves opposite or subopposite, subsequent ones arranged spirally, initially pinnate or bipinnate from the start.

A. lebbeck develops according to Troll's architectural tree model, characterized by only plagiotropic axes and built by continuous superposition of branches thus forming a sympodial stem. Albizia species flower shortly after the appearance of new leaves. In Java A. lebbekoides flowers in March-June and fruits in July-November. In Central Java A. procera flowers in April-June with the major fruit production in August and September, in East Java these periods are January-October and May-October, respectively. Pollination is generally by bees or butterflies, but bird pollination has also been recorded. In species with indehiscent pods the dispersal unit is the entire pod. The dispersal agent is water, except for A. pedicellata for which wind dispersal is reported.

Albizia belongs to the subfamily Mimosoideae and the tribe Ingeae, together with e.g. the genera Archidendron and Paraserianthes. The distinction between the various genera is difficult, and has given rise to a complicated nomenclatural history. Albizia is often misspelled as Albizzia, A. lebbekoides often as A. lebbeckioides.

Ecology

Albizia is usually found scattered or in small groups as a pioneer in open, secondary vegetation or primary deciduous or monsoon forest, savanna and scrub vegetation, from sea-level up to 1700 m altitude; A. chinensis has been cultivated up to 2400 m. They occur in areas with a seasonal climate, often on sandy soils or otherwise well-drained locations. A. dolichadena prefers swamp forest. A. retusa is a littoral species. In the Philippines A. acle is commonly associated with molave (Vitex parviflora A.L. Juss.). In Papua New Guinea A. procera is commonly found in fire-induced grasslands in association with Eucalyptus. Several species can be planted in rocky and shallow sites with a pronounced dry season of at least 4 months.

Silviculture

Albizia is easy to propagate from seed. Direct sowing is often applied, as planting out nursery-grown plants disturbs the long taproot which develops rapidly in young seedlings; in the latter case a survival rate of as low as 4% has been recorded. Some 5-10 seeds per planting hole is usually satisfactory for direct sowing. Cuttings can also be used. Seed should be collected from the tree as it is very susceptible to insect attack and rotting. Seed viability is usually high and seed can be stored for up to 5 years without serious decline in viability. Available seed counts per kg are: A. acle about 240, A. chinensis 49 500-52 000, A. lebbeck 7000-10 500, A. lebbekoides 49 000-59 000 and A. procera 21 000-41 000. Pretreatment of seed with boiling water, concentrated sulphuric acid or by nicking the seed-coat is usually recommended to overcome dormancy, but untreated seed of various species gave 20-80% germination. To assure optimal germination, seeds should be sown in full light. A. lebbeck and A. procera form nitrogen-fixing nodules in the nursery without any inoculation treatment. When sterilized soil was inoculated with Rhizobium obtained from the nodules of a large A. lebbeck tree, however, the seedlings from that tree developed optimally. Seedlings are stumped before planting; in A. lebbeck the stem is cut back to 5 cm, the roots to 15 cm, whereas in A. procera a shoot length of 10-20 cm and a root length of 20-40 cm with a diameter at the collar of 0.5-1.0 cm are recommended. Seedlings up to 1 m tall have been successfully planted as bare-rooted stock. Root cuttings have been successful when taken at least 15 cm long and 1 cm in diameter. In trials in Java the mean annual clear bole volume increment was 7.7-8.5 m³/ha for 15-year-old trees of A. chinensis, 2.8 m³/ha for 12-year-old A. lebbekoides trees and 6.7 m³/ha for 12-year-old A. procera trees. In these trials A. lebbekoides developed a poor stem form due to forking and formation of low and heavy branches. In the Philippines A. chinensis yielded 10-12 m³/ha/year on fertile sites. Lopping the branches for fodder and coppicing are very well tolerated. A rotation of 10-15 years is recommended for A. lebbeck planted for fuelwood, and of 30 years for timber production. The fungus Fusarium oxysporum is a serious disease of several Albizia species, causing gummosis of the vessels and eventually leading to death. In the Philippines the following pests have been observed in A. acle: Lophococcus convexus, a scale insect attacking and killing smaller branches, caterpillars of the faggot worm Clavia cremeri feeding on the leaves, and a flat-headed woodborer, Chrysochroa fulminans, whose larvae feed on the sapwood, possibly girdling the tree inside and whose adults feed on leaves and green bark.

Genetic resources and breeding

In the Philippines A. acle is protected and A. procera is considered a vanishing timber tree.

Prospects

As the timber of several Albizia species, especially that of A. acle and A. procera, is of good quality and growth is moderately fast their potential deserves further exploration.

Literature

12, 47, 101, 130, 162, 193, 198, 209, 218, 234, 238, 259, 260, 261, 267, 300, 304, 308, 333, 341, 343, 344, 348, 387, 402, 405, 406, 432, 436, 464, 488, 526, 536, 632, 633, 677, 678, 696, 697, 736, 740, 741, 780, 804, 816, 829, 831, 839, 857, 861, 865, 899, 910, 933, 934, 955, 970, 974, 1038, 1039, 1086, 1098, 1104, 1163, 1177, 1198, 1199, 1221, 1242.