Aglaia (PROSEA Timbers)

Plant Resources of South-East Asia Introduction

List of species

Aglaia Lour.

Protologue: Fl. Cochinch.: 173 (1790).

Family: Meliaceae

Chromosome number: x= unknown; A. edulis:n= 40, A. elliptica: 2n= 68, A. korthalsiiMiq.: 2n= 84, A. leptantha: 2n= 68, A. odoratissimaBlume: 2n= 84, A. perviridis:n= 20, A. spectabilis:n= 20

Aglaia: medium-heavy to heavy hardwood, e.g. Aglaia cucullata (Roxb.) Pellegrin, A. lawii (Wight) C.J. Saldanha ex Ramamoorthy, A. leptantha Miq., A. pachyphylla Miq., A. silvestris (M. Roemer) Merr., A. spectabilis (Miq.) Jain & Bennet.

• Aglaia: amoora (general)
• Indonesia: parak (general), langsat (Kalimantan)
• Malaysia: bekak, pasak (Peninsular), segera (Iban, Sarawak), langsat-langsat (Sabah), lantupak (Dusun, Sabah)
• Philippines: guijo, makaasim (general), katong (Tagalog). Burma (Myanmar): thanatka-wa
• Cambodia: chomnay poveang
• Thailand: tasua (central), sangkhriat (Trang)
• Vietnam: gội, gội tia, gội trang.

Aglaia currently consists of 105 species, but it is expected that more will be discovered. The species are distributed from southern India and Sri Lanka, through Burma (Myanmar), Thailand, Indo-China towards the Malesian area, northern Australia, New Caledonia, the Solomon Islands, Fiji and Samoa. In general, comparatively few species of Aglaia are endemic; high percentages of endemics are, however, present in New Guinea and Fiji. Within Malesia the largest number of species is found in Borneo (50), followed by Peninsular Malaysia (48), Sumatra (38), the Philippines (35) and New Guinea (33). There is a marked geographical division into species with a western distribution (52 species, confined to the Sunda shelf) and species with an eastern distribution (37 species, confined to Australasia and/or the Pacific).

Aglaia wood is suitable for a wide range of purposes. The heavier timber is used where a good strength and durability are required, as in house and bridge building. The moderately heavy timber is used for light and interior construction. The attractive figure and good working properties of some species make their wood suitable for furniture, flooring, fine finishing, cabinets, turnery, rifle butts, decorative wall panelling, interior trim and face veneer as a substitute for mahogany ( Swietenia spp.). The wood is also used for general construction (beams, joists, rafters, doors and door frames, windows, weatherboards, venetian blinds), joinery, boat building, billiard cue butts, soles, agricultural implements and tool handles. Smaller boles are often used for fences or poles in local house construction.

The fruit and the aril of the seed of some species are edible.

The flowers are aromatic and may be used in tea or to perfume household textiles. The leaves have a wide range of traditional medicinal applications.

Japan imports Aglaia timber mainly from Papua New Guinea and the Solomon Islands. It imports small amounts from other areas (e.g. Thailand). The bulk of the timber is sold in the domestic markets. In Papua New Guinea, Aglaia timber is ranked in the MEP (Minimum Export Price) group 3; in 1992 saw logs fetched a minimum price of US$ 50/m³.

Aglaia yields a medium-weight to heavy hardwood. The heartwood is pale red to dark reddish-brown, sometimes turning to walnut-brown or chestnut-brown, usually distinctly demarcated from the pale yellow to pale red-brown sapwood, but sometimes indistinctly defined. The density is 450-1120 kg/m³at 15% moisture content. The grain is interlocked, sometimes straight, texture moderately fine to moderately coarse. The wood is sometimes glossy, and often has a fragrant, sometimes even pungent, odour when fresh, resembling both cedar and camphor. A regular, diagonal and wavy ribbon figure is generally visible on radial surfaces, and tangential surfaces have an irregular curly figure, marked with characteristic fine zigzag lines formed by cutting through wavy concentric belts of soft tissue.

At 12% moisture content, the modulus of rupture is 81-145 N/mm², modulus of elasticity11 660-15 780 N/mm², compression parallel to grain 46-55 N/mm², shear c. 12.5 N/mm², cleavage 68.5 N/mm tangential, and Janka side hardness 3785 N.

The rates of shrinkage are moderate to fairly high: from green to 15% moisture content 1.4-3.0% radial and 2.7-7.1% tangential, from green to 12% moisture content 2.5-2.9% radial and 4.4-6.9% tangential, and from green to oven dry 4.1-6.8% radial and 6.9-10.7% tangential. The wood usually dries without much degrade, but slight collapse and twisting may occur; stacks should be weighted down to prevent distortion. Boards 75 mm thick take about 6 months to air dry from green to 20% moisture content. The moisture content of green wood is often rather high (94-123% in A. cucullata , but only 71-79% in A. lawii ), and mild kiln schedules are required in drying. Deformation on cross-section (collapse) may be severe during kiln drying (e.g. in A. lawii ). Boards 75 mm thick can be kiln dried from 20% to 12% moisture content in about 4 days. Once dry, form stability is good.

In general, the workability of Aglaia wood is good. The wood machines and saws well, but the heavier wood requires much power in sawing (e.g. A. lawii ). The often curly and wavy grain of the wood requires sharp and fine-set planes, however. Planed surfaces are smooth and lustrous, and finishing gives good results. The wood peels and slices satisfactorily. It has been suggested that only a limited number of species may be used for first grade face veneer, but this has not been confirmed. Veneer may warp severely during drying. Unbleached pulp is not very bright, but is very strong. The sawdust of several species may cause dermatitis.

The wood is rated as moderately durable to durable, even in contact with the ground, but for some species it is rated as non-durable and susceptible to Lyctus attack (e.g. A. argentea ) and sometimes also to pinhole borer and termite attack. The wood may be susceptible to staining. The heartwood is often very difficult to treatment with preservatives, the sapwood moderately easy to easy. A test of A. cucullata heartwood showed a retention of 62 kg/m³using the pressure treatment method, and 407 kg/m³for sapwood; heartwood of A. lawii absorbed only 20 kg/m³, and sapwood 327 kg/m³. Treatment of green logs or sawn timber by the boron diffusion process is recommended.

Aglaia wood contains 67.5-74% holocellulose, 46.5-50%α-cellulose, 32.5-37% lignin, c. 12% pentosan and 0.3-1.1% ash. The solubility is 1.1-3.6% in alcohol-benzene, 2.1-5.6% in hot water, and 8.8-19.6% in a 1% NaOH solution.

Dioecious, usually small or medium-sized trees, sometimes large and up to 40(-50) m tall, rarely shrubs; bole unbranched for up to 24 m, up to 160(-200) cm in diameter, often with small to tall (up to 3(-5) m high) buttresses; bark surface with scattered large lenticels and smaller ones in longitudinal rows, otherwise smooth or, in larger trees, often with deciduous squarish scales, inner bark yellowish-brown; latex rarely present in bole bark; in some species which become small trees only, twigs contain latex, sometimes abundantly; crown sympodial; apical bud consisting of 2-4 slender unexpanded leaves, without bud scales. Indumentum consisting of stellate hairs or stellate or peltate scales present, at least on the younger parts. Leaves arranged spirally, usually imparipinnate with 3-27 leaflets, rarely with a single leaflet, lacking stipules; leaflets entire, the apex acuminate to caudate with an obtuse to acute acumen. Inflorescence usually axillary, occasionally ramiflorous or cauliflorous; male inflorescence large, much divaricately branched, with up to several thousand flowers; female inflorescence similar but usually smaller, sometimes a narrow spike-like raceme. Flowers unisexual, with well developed rudiments of the opposite sex, 3(-4) or 5(-6)-merous; calyx cup-shaped, often thickened at base; petals free or united at base, subrotund, elliptical or obovate, often yellow, sometimes white or pink; stamens united to form a tube, anthers (3-)5-10(-21), usually in a single whorl, inserted on the inner face of the tube, usually glabrous; ovary superior, 1-3(-10)-locular, style short or absent, style-head small, capitate, conical or clavate; disk absent. Fruit a 1-4(-6)-seeded, more or less globose to pear-shaped berry, nut or less frequently a 1-3(-4)-valved capsule, each locule with 1(-2) seeds. Seeds large, usually with an aril nearly or completely covering the seed, without endosperm.

• Macroscopic characters:

Heartwood usually dark brown or reddish-brown with purple tinge, occasionally pale brown or yellowish-brown; sapwood pale yellowish to greyish or pinkish-brown. Grain slightly to moderately interlocked. Texture moderately fine to moderately coarse; wood sometimes slightly lustrous; fresh wood often with fragrant odour. Growth rings indistinct; vessels visible to the naked eye; parenchyma in fine tangential bands, or invisible; rays almost invisible to the naked eye; ripple marks absent.

• Microscopic characters:

Growth rings absent. Vessels diffuse, 8-9(-11)/mm², solitary (25-60%) or in multiples of 2-4(-5), uniformly distributed, generally oval, average tangential diameter (75-)115-155μm; perforation plates simple; intervessel pits dense and alternate, 3-4μm in diameter; vessel-ray pits similar but half-bordered, brown deposits present; tyloses absent. Fibres 1.0-1.6 mm long, septate, thick-walled (c. 3μm), 15-25μm in tangential diameter, with minutely bordered to simple pitsmainly in the radial walls. Axial parenchyma paratracheal, vasicentric and aliform to confluent; apotracheal parenchyma diffuse, in strands of 4-8 cells. Rays multiseriate (40% to more than 80%) or uniseriate, multiseriate rays 2-3 cells wide, up to 0.6 mm high, heterocellular with 1-2(-3) rows of square to upright marginal cells, uniseriate rays short, mostly less than 0.4 mm high. Prismatic crystals often present in non-chambered parenchyma cells (absent in A. sapindina ). Silica bodies absent.

Species studied: A. beccarii C.DC., A. edulis , A. lawii , A. malaccensis , A. odorata , A. odoratissima , A. rimosa , A. sapindina .

Germination is semi-hypogeal, with the hypocotyl undeveloped and with peltate cotyledons. When the shoot axis begins to grow, the cotyledons are forced apart, the testa splits, and the cotyledons are exposed. The cotyledons remain on the soil surface. The first 2 leaves are simple and opposite, subsequent leaves are arranged spirally, simple at first, later with 2-3 leaflets. The number of leaflets increases to or even exceeds the number of leaflets on the mature plant.

In trial plantations of A. lawii in Java the mean height 10 years after planting was 10 m and the mean diameter was 10-12 cm.

Growth is usually sympodial with orthotropic branching. Some of the smaller species are monopodial and belong to Corner's tree architecture model. When the apical shoot is damaged, an axillary bud grows to form a new apical meristem.

Aglaia species usually flower around June and bear fruit in October to November. The bright-coloured perianth and the strong scent, especially in male flowers, attracts insects collecting pollen. Fruits did not develop when pollination was prevented. Small insects, probably mainly dipterans, are most likely the main pollinators of Aglaia flowers. Two main types of fruits can be distinguished: dehiscent fruits containing seeds with a red odourless aril which are dispersed by birds, and indehiscent fruits containing seeds with a white, yellow, orange or brown and sweet-tasting aril, which are dispersed by primates.

Aglaia belongs to the tribe Aglaieae and is most closely related to the genus Lansium . The latter differs from Aglaia by its indumentum of simple hairs, its 5-locular ovary and the structure of the style and style-head. Aglaia is divided into 2 sections on the basis of whether the fruits are dehiscent. Section Amoora (Roxb.) Pannell with dehiscent fruits was formerly regarded as a separate genus and coincides more or less with the timber trade group amoora, which is often kept separate from the trade group aglaia in Papua New Guinea. Amoora timber is slightly less heavy and paler in colour, but there is much overlap with aglaia timber. Several botanists disagree with the merging of Amoora into Aglaia , arguing that Amoora trees can be easily distinguished in the forest by their larger size and little latex. Aglaia sensu stricto consists mainly of small laticiferous trees.

The exact type of indumentum of stellate hairs and/or scales is an important, often diagnostic feature for identification of species.

Aglaia usually occurs scattered and is locally common but never dominant. It is found in both primary and secondary forest, generally in evergreen rain forest or sometimes in monsoon or deciduous forest. Larger adult individuals may become canopy trees but generally they are elements of the subcanopy layer. Most species prefer flat or slightly undulating land, often along rivers, or in swamp forest in periodically inundated locations, sometimes in kerangas. Aglaia is usually found from near the coast, on coastal plains, towards the lower montane zone up to 1500 m altitude, but occasionally individual species ascend as high as 2500(-3800) m. The preferred soils are usually sandy to loamy or clayey, but many species also occur on limestone or on granitic soils.

Per kg there are about 380 green seeds of A. lawii . The seed does not need any pretreatment before being sown in full light and is sown as soon as possible after harvesting. There is no information on the longevity of the seed. Germination period and germination percentage have been determined for some species: seed of A. forbesii with pulp has nearly 100% germination in 30-81 days and seed without pulp has 30% in 31-40 days. Other germination rates are: 45% for A. leucophylla in 47-121 days, 22% for A. macrostigma King in 30-68 days, 85% for A. malaccensis in 13-44 days (seed in aril), 100% for A. silvestris in 27-43 days, and 76% for A. spectabilis in 8-46 days; A. lawii has 50% germination.

A. lawii has been planted on an experimental scale in Java. The trees developed somewhat crooked stems, and branches developed very low along the stem; the latter was attributed to the wide spacing adopted. In natural forest in Papua New Guinea, Aglaia constitutes up to 5% of the gross timber volume. Natural regeneration in forest with a closed canopy is generally satisfactory. Survival of A. argentea seedlings in natural forest in Irian Jaya was very low due to its slow growth; the initial 480 seedlings/ha declined to 0.5 trees/ha.

Seed of Aglaia is sometimes destroyed by larvae of various groups of insects, including moths, flies and beetles, developing from eggs laid in the young fruits.

A clear bole of A. cucullata 24 m long, with a diameter of 78 cm at breast height and of57 cm under the first branch, had a volume of 8.6 m³. A bole of A. lawii 15 m long, with a diameter of 60 cm at breast height and of 51 cm under the first branch, had a volume of 3.6 m³. In Papua New Guinea, the estimated timber volume of A. cucullata is up to 1.1 m³/ha, and in New Britain up to 2.7 m³/ha has been recorded. The estimated timber volume is up to 0.7 m³/ha for all other Aglaia spp. in Papua New Guinea. In the Elmerrillia ovalis (Miq.) Dandy forest in North Sulawesi, the estimated timber volume of Aglaia spp. is 1.2-2.4 m³/ha.

Several species of Aglaia show considerable morphological variation, which is often correlated with geographical distribution. Possible future germplasm collection activities should take this into account. Because of the comparatively high percentage of endemic species of Aglaia present in New Guinea, individual species may easily become endangered here as a result of selective logging and the conversion of natural forest into agricultural land or production forest.

For breeding purposes it is important to know that Aglaia is reported to have polyploid series.

As the wood of Aglaia is of great decorative value and often has good physical and mechanical properties which allow for wide utilization, it is probable that trials will be set up to test the species in plantations or enrichment planting.

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