Paraserianthes (PROSEA)

Plant Resources of South-East Asia
Introduction

List of species

Paraserianthes Nielsen

Protologue: Bull. Mus. Natn. Hist. Nat., 4e sér., sect. B, Adansonia 5: 326 (1983).

Family: Leguminosae

Chromosome number: x= 13; P. falcataria subsp.falcataria: 2n= 26

Trade groups

Batai: lightweight timber, e.g. Paraserianthes falcataria (L.) Nielsen.

Vernacular names

Batai

Brunei: puah
Indonesia: jeungjing (general), sengon laut (Java), sika (Moluccas)
Malaysia: kayu machis (Sarawak)
Papua New Guinea: white albizia
Philippines: Moluccan sau, falcata.

Origin and geographic distribution

Paraserianthes consists of 4 species. It is native to Sumatra, Java, Bali and Flores, the Moluccas, New Guinea, the Solomon Islands and Australia. Its origin probably lies in the eastern Malesian area as the largest diversity is found here. The peculiar disjunct distribution of the two subspecies of P. lophantha (Willd.) Nielsen (south-western Australia and Sumatra, Java, Bali and Flores, respectively), a shrub or small tree, is thought to have originated from a once more continuous distribution, probably during the cooler and less humid glacial periods in the Pleistocene. At present species of this genus are widely planted throughout the tropics.

Uses

The comparatively soft wood of batai is suitable for general utility purposes such as light construction, especially rafters, panelling, interior trim, furniture and cabinet work. As the wood is not durable and susceptible to various kinds of insect and fungal attacks, it should be used under cover and not in contact with the ground. It is useful for lightweight packing materials such as packages, boxes, cigar and cigarette boxes, crates, tea chests and pallets. It is a well-known source for matches. Because the wood is fairly easy to cut, batai is also suitable for wooden shoes, musical instruments, toys and novelties, forms and general turnery. Batai is an important source of lightweight veneer and plywood and is very suitable for the manufacture of light- and medium-density particle board, wood-wool board and hardboard and has recently also been used for blockboard. The wood is also fairly extensively used to supply pulp for the manufacture of paper and has been used for the manufacture of viscose rayon. Batai is commonly planted for reforestation and afforestation of vacant and denuded forest lands and for firewood and charcoal production, although it is generally not valued as firewood. Its suitability as a shade tree for tea and other crops is limited because solitary trees are easily damaged by wind.

The leaves are sometimes used as a fodder for chickens and goats. The bark is reported to serve for tanning nets in Ambon, and it is sometimes used locally as a substitute for soap. It is also stripped from the tree and used for packing purposes. The pods have been used as a substitute for peté beans (Parkia speciosa Hassk.).

Production and international trade

In Japan there is a great demand for batai wood for manufacture of lightweight furniture and furniture components (e.g. drawer sides); the butt log portion is used particularly for these purposes. Timber from natural and plantation-grown trees is imported in Japan, but no statistics are available.

Properties

Batai is a lightweight, soft to moderately soft wood. The colour of the heartwood ranges from whitish to pale pinkish-brown or light yellowish- to reddish-brown (in older trees); the heartwood of younger trees is not clearly demarcated from the sapwood (pale coloured), but it is more distinct in older trees. The density is (230-)300-500 kg/m³ at 12% moisture content. The grain of the wood is straight or interlocked, texture moderately coarse but even.

At 12% moisture content the modulus of rupture is 48-58 N/mm², modulus of elasticity 6900-8830 N/mm², compression parallel to grain 27(-58) N/mm², compression perpendicular to grain 2 N/mm², shear 6-9 N/mm², cleavage (at 15% moisture content) 33 N/mm radial and 35.5 N/mm tangential, Janka side hardness 1165 N at 15% moisture content and 2000 N at 12% moisture content, and Janka end hardness (at 15% moisture content) 2175 N.

The rates of shrinkage are moderate, from green to 12% moisture content 1.1-2.1% radial and 2.6-4.0% tangential, and from green to oven dry (2.1-)2.5-3.4% radial and (3.6-)5.0-6.5% tangential. Batai wood usually air dries fairly rapidly without serious degrade, and the kiln- drying properties are satisfactory. The most common drying defect is bowing. Boards of 12 mm thick air dry in about one month, but boards of 40 mm thick may take 2.5-3 months to air dry from green to 15% moisture content. Boards of 2.5 cm thick can be kiln dried to 10% moisture content in 4 days, at a temperature of 49-77° C and corresponding moisture content of 79% to 33%. The stability of the wood after drying is good; movement in service is small.

Batai is easy to work with machines and hand tools, but, although the wood is non-siliceous, it is reported to be abrasive to saws due to pinching and subsequent burning of sawteeth as a result of tension stresses relieved in the wood. Sharp knives are needed to produce smooth surfaces in planing; if not, grain may pick up badly after planing, especially on radial surfaces. Best planing results are obtained when a 20° cutting angle is used. The wood moulds and mortises well but tension wood, if present, will give a woolly surface. Boring is usually easy, but the nailing properties are rated as poor. Gluing is no problem. Batai peels and slices easily without pretreatment into veneer of 0.8 mm or 1.6 mm thick; the veneer produced is of good quality, light and smooth, with curly figure, and can be dried easily. Batai is very suitable for low- and medium-density particle boards (density 427-613 kg/m³). The pulping characteristics of the wood are excellent; batai is listed among the best tropical woods recommended for pulping. The strength properties of kraft and soda pulps are comparable to good-quality eucalypt pulp, and the neutral sulphite semi-chemical process also produces pulp with excellent strength properties. Only minimum bleaching is required to achieve high-quality, white paper, because of the paleness of the wood.

Batai wood is not durable when used outside. Graveyard tests in Indonesia showed an average service life in contact with the ground of 0.5-2.1 years. It is often highly vulnerable to attack by termites, powder-post beetles and fungi. The wood can be treated easily with preservatives by the open tank procedure and using a mixture of creosote and diesel fuel. Stake tests showed an average life in contact with the ground of 15 years under tropical conditions when the stakes had been treated with preservatives.

Sawdust from dry wood may cause allergic reactions and may irritate nose and throat. Batai wood contains 49% cellulose, 27% lignin, 15.5% pentosan, 0.6% ash and 0.2% silica. The solubility is 3.4% in alcohol-benzene, 3.4% in cold water, 4.3% in hot water and 19.6% in a 1% NaOH solution. The energy value of the wood is 19 500-20 600 kJ/kg.

Description

Unarmed trees (or shrubs) up to 40 m tall; bole generally straight and cylindrical in dense stands, branchless for up to 20 m and up to 100 cm or sometimes more in diameter; buttresses small or absent; bark surface white, grey or greenish, smooth or slightly warty, sometimes shallowly fissured and with longitudinal rows of lenticels, inner bark white, yellowish, pink or pale red-brown, fibrous; young parts often densely tomentose.
Leaves alternate, bipinnate, the rachis and pinnae with extrafloral nectaries; stipules linear or filiform, caducous; leaflets opposite, many.
Inflorescence axillary, consisting of pedunculate spikes or racemes, the spikes sometimes arranged in panicles.
Flowers bisexual, regular, 5-merous, subtended by bracts; calyx valvate, gamosepalous, tubular to cup- or bell-shaped; corolla valvate, gamopetalous, funnel- or bell-shaped, creamy to yellowish; stamens numerous, the filaments united at base into a tube which is shorter or longer than the corolla, anthers quadrangular, minute, opening by longitudinal slits; ovary solitary, shortly stipitate or sessile, glabrous.
Fruit a chartaceous, flat, straight pod, not segmented, dehiscent along both sutures, many-seeded.
Seed subcircular to oblong, flat to convex, without aril, with a thick sclerified exotesta, not winged; endosperm absent; cotyledons large.
Seedling with epigeal germination; cotyledons stipulate, sessile; first two leaves opposite or arranged spirally, pinnate or bipinnate, subsequent leaves bipinnate.

Wood anatomy

Macroscopic characters

Demarcation between sapwood and heartwood usually indistinct, heartwood white to pale pink or light reddish-brown, with little figure or no figure at all.
Grain usually interlocked, sometimes straight.
Texture moderately coarse and even.
Growth rings indistinct; vessels readily visible to the naked eye, without deposits; parenchyma paratracheal and sparse, visible with a 10× hand lens as distinct sheaths to the vessels, and diffuse, appearing as small white dots at cross-section; rays fine and visible with a lens at cross-section.
Ripple marks absent.

Microscopic characters

Growth rings indistinct.
Vessels diffuse, 1-3(-4)/mm², solitary and in radial multiples of 2(-3), mostly circular to oval, average tangential diameter 160-340μm, perforations simple; intervessel pits alternate, vestured, round to polygonal, 5-8μm; vessel-ray and vessel-parenchyma pits similar to intervessel pits, but half-bordered; helical thickenings absent; tyloses absent.
Fibres 1200-1500μm long, non-septate, thin-walled, with simple to minutely bordered pits mainly confined to radial walls, with tendency to storied structure.
Parenchyma scanty, paratracheal, vasicentric and diffuse.
Rays 6-12/mm, narrow, mainly uniseriate, with some 2-seriate rays (c. 20%), 300-400(-500)μm high, homogeneous.
Prismatic crystals in long vertical strands in diffuse parenchyma.
Brownish deposits abundant in ray cells.

Species studied: P. falcataria.

Growth and development

Batai grows so fast that it is sometimes called "miracle tree". P. falcataria is even mentioned in the Guinness Book of Records as the world's fastest growing tree. On good sites, trees may attain a height of 7 m in a little more than one year. Trees reach a mean height of 25.5 m and a bole diameter of 17 cm after 6 years, 32.5 m high and 40.5 cm diameter after 9 years, 38 m high and 54 cm diameter after 12 years, and 39 m high and 63.5 cm diameter after 15 years. Growth of young trees in a phosphorus-deficient soil is promoted by inoculation with mycorrhizal fungi; Glomus fasciculatum and Gigaspora margarita, in combination with Rhizobium have proved to be effective. Nitrogen-fixing nodules containing leghaemoglobin are found on roots.

Trees may already flower at the age of 3 years. Two flowering periods per year have been observed in Peninsular Malaysia and Sabah. Ripe pods appear approximately 2 months after flowering. The pods dehisce when ripe, often still attached to the tree, scattering the seeds on the ground.

Other botanical information

The genus Paraserianthes belongs to the tribe Ingeae (subfamily Mimosoideae) and was recently separated from Albizia. Apart from Albizia, its closest relatives are Serianthes (especially S. minahassae (Koord.) Merr. & Perry), and Archidendropsis (especially subgenus Basaltica Nielsen). These relationships are mainly based on pollen morphology but are often supported by similarities in wood anatomy. The genus Paraserianthes is subdivided into 2 sections: section Paraserianthes and section Falcataria Nielsen. The first section comprises only the species P. lophantha and is distinguished by its solitary, axillary, not paniculate racemes and its pollen with costae (pores surrounded by distinct thickenings).

Ecology

The four species of Paraserianthes occur in a wide variety of habitats generally ranging from sea-level to 1600 m but sometimes up to 3300 m altitude. As they are pioneers, they occur in primary but more characteristically in secondary lowland rain forest, but also in light montane forest, elfin forest and grassy plains or along roadsides near the sea. They are found on sandy and lateritic soils as long as drainage is sufficient. The species are adapted to perhumid to monsoon climates (with a dry season of up to 4 months). In their natural habitat, the annual precipitation may range between 2000-2700 mm or sometimes up to 4000 mm. The optimal temperature range is 22-29° C with a maximum of 30-34° C and and a minimum of 20-24° C. In natural stands in Irian Jaya P. falcataria is associated with species such as Toona sureni (Blume) Merr., Terminalia spp., Celtis spp., Agathis labillardieri Warb., Pterocarpus indicus Willd. and Diospyros spp.

When planted, P. falcataria is able to grow on comparatively poor sites and to survive without fertilization. However, it does not thrive in poorly drained, flooded or waterlogged areas.

Propagation and planting

Batai is strongly light-demanding and regenerates naturally only when the soil is exposed to sunlight. In the forest, wildlings sprout in abundance only when the canopy is open and when the soil is cleared from undergrowth. Wildlings can be successfully collected and potted for planting, but they are delicate and have to be handled carefully.

Seeds are difficult to collect from the ground since they are small. The weight of 1000 seeds is 16-26 g. Usually they are collected by cutting down branches bearing ripe brown pods. The seeds can easily be collected from felled trees if the fruits happen to be in the right condition. Untreated seeds germinate irregularly; germination may start after 5-10 days but sometimes it is delayed for up to 4 weeks from sowing. To hasten germination and to make it more simultaneous, seeds can be treated by soaking them in boiling water for 1-3 minutes, or by immersion in concentrated sulphuric acid for 10 minutes and subsequent washing and soaking in water for 18 hours. The germination rate can be as high as 80% to almost 100%. Seeds of batai are usually sown by broadcasting, pressed gently into the soil, and then covered by a layer of fine sand up to 1.5 cm thick.

For storage, seeds are air dried for 24 hours and then packed in polyethylene bags. When stored at 4-8C, the germination rate after 18 months may still be 70-90%.

The soil in the seed-bed must be loose and well-drained; application of a surface layer of mulch is advisable and excessive shading should be avoided. The seedlings can be transplanted when they have reached a height of 20-25 cm with a woody stem and a good fibrous root system; this stage can be reached in 2-2.5 months. Container plants are often transplanted into the field when 4-5 months old. The stem is cut back to about 10 cm above the root collar, and the taproot to a length of about 22 cm. The seedlings are usually planted into the field with a spacing of 2 m × 2 m to 4 m × 4 m. The average yearly production of batai seedlings in the Philippines was 2.1 million in the period 1979-1982.

Seed tissue of batai has been successfully used for propagation by tissue culture in the Philippines.

Silviculture and management

Batai plantations should be kept weed-free during the first few years. The application of fertilizers may improve the yield; application of 12.5 kg/ha of P was found satisfactory. When the stand (for timber production) is 4-5 years old, it can be thinned to a density of 250 stems/ha, and after 10 years to 150 stems/ha. When the trees are grown for timber production, artificial pruning is necessary, as they have a tendency to fork. The cutting cycle is usually 12-15 years. Trees grown for pulp production have a cutting cycle of about 8 years.

Batai is commonly used in agroforestry systems, usually in a cutting cycle of 10-15 years, in combination with annual crops in the first year and grazing animals in subsequent years. Pure stands give a good protective cover to prevent erosion on slopes, and they are recommended for this purpose in the Philippines on catchment areas sheltered from typhoons. Batai trees coppice fairly well, which is advantageous for pulpwood production, but they are very susceptible to fire.

Diseases and pests

In 1988 and 1989 gall rust disease caused by Uromycladium tepperianum provoked severe damage in Bukidnon Province (Mindanao, the Philippines). The government banned the transport of logs in and out of Bukidnon Province, and planting was suspended.

Nursery seedlings are susceptible to damping-off caused by fungi of Rhizoctonia, Sclerotium, Fusarium, Pythium and Phytophthora. Sterilizing the soil before sowing and applying fungicides to soil and seeds may control the disease. The fungus Corticium salmonicolor causes a disease known as pink canker or salmon canker. At first, light brown lesions appear on the bark of young trees; they gradually enlarge and develop cracks, the colour turns to pale salmon or pinkish and then mycelium mats appear around the lesions. The disease may seriously damage plantations. Plantations can also suffer from other fungal diseases like red root caused by Ganoderma pseudoferrum. An anthracnose seedling disease caused by a Colletotrichum species has been observed in Sumatra.

Plantation pests in Malaysia, Indonesia and the Philippines include stem-borers such as the longicorn beetle Xystrocera festiva and the red borer Zeuzera coffea (a cossid moth). Leaf-eating caterpillars (e.g. Eurema blanda, E. hecabe and Semiothesa emersaria) may attack seedlings and trees. Aphids have occasionally been a problem on seedlings. Insecticides are commonly used to control these pests.

Harvesting

Plantations are clear-cut when the cutting age is reached. Usually harvesting is problem-free as the trees are harvested when still comparatively young and consequently have small and lightweight logs which can be yarded and loaded easily. Rapid extraction, conversion and seasoning of batai wood is necessary to prevent insect attack and infection with fungi. The wood is particularly prone to sap-stain attack.

Yield

Batai is a fast grower and the yield is often high. In 8-12-year rotations, mean annual volume increments of (10-)25-30(-40) m³/ha are attained. On fertile soils in Indonesia, mean annual increments of 50-55 m³/ha have even been reached in plantations of 9-12 years old (120 trees/ha when 9 years old and 76 trees/ha when 12 years old).

Genetic resources

Batai is planted on a large scale all over the tropics and the genetic resources are quite comprehensive. P. pullenii is endemic to Papua New Guinea, where it occurs very locally and might be liable to genetic erosion or extinction.

Prospects

Breeding programmes should be conducted to obtain superior trees in respect to shape of bole (preferably without a tendency to fork and long and straight) and resistance to diseases and pests. Superior trees can be mass produced by tissue culture.

Literature

Chauhan, L. & Dayal, R., 1985. Wood anatomy of Indian Albizias. IAWA (International Association of Wood Anatomists) Bulletin 6(3): 213-218.
Dayan, M.P., 1989. Moluccan sau - Albizia falcataria (L.) Back. RISE (Research Information Series on Ecosystems) Vol. 1(10): 84-97.
Eusebio, M.A., Sinohin, V.O. & Dayan, M.P., 1990. Gall rust disease of Albizia falcataria (L.) Back. RISE (Research Information Series on Ecosystems) Special Issue. 14 pp.
Griffioen, K., 1954. Albizzia falcata, een goede industrie-houtsoort [Albizzia falcata, a good industrial wood species]. Tectona 43: 97-110.
Lamprecht, H., 1989. Silviculture in the tropics. Deutsche Gesellschaft für Technische Zusammenarbeit (GTZ), Eschborn. pp. 237-238.
Martawijaya, A., Kartasujana, I., Mandang, Y.I., Prawira, S.A. & Kadir, K., 1989. Atlas kayu Indonesia [Indonesian wood atlas]. Vol. 2. Forest Products Research and Development Centre, Bogor. pp. 59-64.
Natawiria, D., 1973. Pests and diseases of Albizia falcataria (A. falcata). Rimba Indonesia 17: 58-69.
National Academy of Sciences, 1979. Tropical Legumes: resources for the future. Washington, D.C. pp. 173-177.
Nielsen, I., Guinet, Ph. & Baretta-Kuipers, T., 1983. Studies in Malesian, Australian and Pacific Ingeae (Leguminosae-Mimosoideae): the genera Archidendropsis, Wallaceodendron, Paraserianthes, Pararchidendron and Serianthes, part 2. Bulletin du Muséum National d'Histoire Naturelle, 4e sér., sect. B, Adansonia 5: 335-360.
Peh, T.B. & Khoo, K.C., 1984. Timber properties of Acacia mangium, Gmelina arborea, Paraserianthes falcataria and their utilization aspects. Malaysian Forester 47: 285-303.

Selection of species

Authors

J.P. Rojo (general part, wood anatomy, selection of species),
D.S. Alonzo (properties)
J. Ilic (wood anatomy)