Intsia bijuga var. bijuga

Family

Caesalpiniaceae (Leguminosae - Caesalpinioideae)

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Chromosome number

2n = 24

Synonyms

Afzelia bijuga (Colebr.) A.Gray (1854).

Vernacular names

Origin and geographic distribution

Intsia bijuga is very widespread in coastal regions of islands in the Indian and Pacific Oceans, including eastern Madagascar and the Seychelles. It has been planted near the sea-shore in Tanzania and in Mauritius.

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Uses

In Madagascar the wood of Intsia bijuga, known as ‘hintsy’, is highly prized for heavy carpentry, construction including naval construction, flooring, joinery, doors, furniture, railway sleepers, vats, shingles and decorative purposes. It is considered one of the best woods available in the eastern lowlands, being beautiful and strong. Traditionally, it has been used for coffins and canoes.
In tropical Asia, the wood is known as ‘merbau’ together with the wood of Intsia palembanica Miq. Merbau is important on the international timber market. It is a very good general-purpose timber because of its favourable physical and mechanical properties, combined with a high natural durability and an attractive appearance. It is used in house building, especially for high-class exterior joinery such as windows, solid panel doors, framing and weatherboarding, for waterwork construction such as bridges, wharves, sluices and sheet piles, and for high-grade flooring. In the Samoa and Fiji islands, the wood is used for house posts, furniture and traditional carved bowls.
In Madagascar Intsia bijuga is planted in fences and in reforestation programmes, and the fruits serve as laxative. The bark contains tannin and has been used for producing reddish brown dyes. In tropical Asia the seeds are occasionally eaten after careful preparation; they are soaked in salt water for 3–4 days and then boiled. Bark and leaves are used medicinally against rheumatism, diarrhoea and urinary diseases. The seed oil can be used as an insect repellent for stored products; its activity is comparable to that of neem (Azadirachta indica A.Juss.).

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Production and international trade

The trade in merbau timber (comprising several Intsia spp., mainly Intsia bijuga and Intsia palembanica) is considerable. The major producing countries are Indonesia, Malaysia and Papua New Guinea, and the major importers are China, India and the European Union. In 2007 registered merbau export from Indonesia was nearly 250,000 m³. In 2006 export from Papua New Guinea was 89,000 m³. Malaysia produced about 100,000 m³ of merbau in 2006, mainly from Peninsular Malaysia, at an average export price of US$ 663/m³. Peninsular Malaysia reached its maximum annual production in 1989 with 246,000 m³. In 2010 the price of merbau sawn wood was about US$ 520/m³.
Exports of Intsia bijuga wood from Madagascar are small. In 2007 China imported 250 m³ from Madagascar on a total of 105,000 m³ of merbau import (68% of the total as round logs, 32% sawn timber). The import of merbau wood by the European Union in 2005 was approximately 25,000 m³.

Properties

The heartwood is yellow-orange to red-brown, darkening upon exposure, and distinctly demarcated from the whitish, 4–8 cm wide sapwood. The grain is usually straight, sometimes wavy or interlocked, texture moderately coarse and even. The wood is often without lustre, sometimes slightly lustrous on quarter-sawn surfaces and with an attractive figure. It feels slightly oily to the touch.
Wood from Madagascar has the following properties. It is heavy, with a density of 780–930 kg/m³ at 12% moisture content, and hard. The wood air dries slowly, but with little degrade. It kiln dries fairly well, but mild kiln schedules are required to obtain good results when drying thicker boards. The rates of shrinkage are low, from green to oven dry (1.8–)2.7–4.0% radial and 3.7–7.1% tangential. Once dry, the wood is moderately stable to stable in service.
At 12% moisture content, the modulus of rupture is 152–210 N/mm², modulus of elasticity 12,550–16,000 N/mm², compression parallel to grain 63–84 N/mm², shear 8–10 N/mm², cleavage 14–24 N/mm and Chalais-Meudon side hardness 6.1–10.
The wood generally saws and works well, but it may cause dulling of saw teeth and cutting edges; it may be hard to work with hand tools. The surface of fresh wood may be marred by an oily exudate, and during sawing the saw teeth may become covered with a gummy substance. A reduction of the cutting angle of 20° is advantageous in planing quarter-sawn material with interlocked grain to prevent picking-up of grain. Pre-boring for nailing and screwing is advisable; the holding power for nails and screws is good. Boring and turning give no problems and generally a smooth finish. The wood stains and polishes satisfactorily, but requires considerable filling. It usually glues satisfactorily with most modern types of glue. It is difficult to cut or slice into veneer, even after pre-steaming, mainly due to its high density. When in contact with water, water-soluble extractives create blackish-lined dark-coloured spots on the surface which are very difficult to remove. Manufactured exterior joinery products have to be protected from water on building sites. The wood does not corrode iron, but it does stain black in the presence of iron and moisture.
The heartwood is durable, being resistant to fungal, termite and powder-post beetle attacks. The sapwood is liable to Lyctus. The heartwood is fairly resistant to marine borers, with a service life in sea water of about 3 years. The heartwood is very difficult to treat with preservatives. The sawdust may cause irritation.
The wood contains 28–43% cellulose, 21–25% lignin, 14–17% pentosan, 1.1–1.5% ash and little silica. The solubility is 9–22% in alcohol-benzene, 5–8% in hot water and 19.5–27.5% in a 1% NaOH solution.

Adulterations and substitutes

The wood of Intsia bijuga resembles that of African Afzelia spp., both in aspect and properties, and is used for similar purposes.

Description

Semi-deciduous, small to medium-sized tree up to 30(–40) m tall; bole often low-branching but sometimes branchless for up to 18 m, up to 80(–120) cm in diameter, often buttressed in older trees; bark surface smooth, pale grey to pale brown, inner bark thick, fibrous, pale red to pale yellowish brown; crown rounded to umbrella-shaped, dense; twigs glabrous. Leaves alternate, paripinnately compound with (1–)2–3 pairs of leaflets; stipules fused at base, forming a persistent scale; petiole thick, 1–2 cm long, rachis up to 8 cm long; leaflets asymmetrically ovate or elliptical to nearly round, 4–16 cm × 3–11 cm, obtuse to rounded, often slightly notched at apex, margins entire, leathery, glabrous, pinnately veined with 12–20 pairs of lateral veins. Inflorescence a terminal panicle up to 10 cm long, short-hairy. Flowers bisexual, zygomorphic, whitish; pedicel 3–5 mm long, with 2 deciduous bracteoles; hypanthium elongate, 6–8 mm long; sepals 4, unequal, ovate, 6–16 mm × 4–6 mm, short-hairy; petal 1, 1–3 cm long, with claw at base and crisped lamina broader than long, white tinged yellow or pink; stamens 3, c. 4 cm long, hairy, purple-red, staminodes 4–7, c. 1 cm long; ovary superior, compressed spindle-shaped, 2–3 mm long, hairy, 1-celled, with c. 2 mm long stipe, style up to 4 cm long. Fruit an oblong, flattened pod 7–28 cm × 3–7 cm, glabrous, pale brown, with slightly raised veins, tardily dehiscent with 2 leathery to woody valves, up to 6-seeded. Seeds discoid to oblong, 1.5–3.5 cm × 1–3 cm, dark brown, more or less covered with detachable rusty brown scurf. Seedling with epigeal germination.

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Other botanical information

Intsia comprises 3 species centred in tropical Asia, with Intsia bijuga reaching tropical Africa. Intsia is closely related to Afzelia. The latter genus differs by its usually more numerous leaflets and fertile stamens, and by its seeds having an aril.

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Anatomy

Wood-anatomical description (IAWA hardwood codes):
Growth rings: 2: growth ring boundaries indistinct or absent. Vessels: 5: wood diffuse-porous; 13: simple perforation plates; 22: intervessel pits alternate; 23: shape of alternate pits polygonal; 25: intervessel pits small (4–7 μm); 29: vestured pits; 30: vessel-ray pits with distinct borders; similar to intervessel pits in size and shape throughout the ray cell; 42: mean tangential diameter of vessel lumina 100–200 μm; 46: ≤ 5 vessels per square millimetre; (58: gums and other deposits in heartwood vessels). Tracheids and fibres: 61: fibres with simple to minutely bordered pits; 66: non-septate fibres present; 69: fibres thin- to thick-walled. Axial parenchyma: 80: axial parenchyma aliform; 81: axial parenchyma lozenge-aliform; (82: axial parenchyma winged-aliform); (83: axial parenchyma confluent); (89: axial parenchyma in marginal or in seemingly marginal bands); 91: two cells per parenchyma strand; 92: four (3–4) cells per parenchyma strand. Rays: 97: ray width 1–3 cells; 104: all ray cells procumbent; 115: 4–12 rays per mm. Mineral inclusions: 136: prismatic crystals present; 142: prismatic crystals in chambered axial parenchyma cells.
(F.D. Kamala, P.E. Gasson & E.A. Wheeler)

Growth and development

In Indonesia, an 8-year-old stand had an average height of 10.7 m with an average bole diameter of 15 cm. In Madagascar, under optimal conditions in regions with high annual rainfall, growth can be up to 1 m per year in full sun, but trees planted in the shade have been recorded to reach an average height of 1.4 m only after 7 years. In enrichment plantings in Madagascar, the average height of Intsia bijuga trees 5 years after sowing was 3 m and the average stem diameter 4 cm; after 10 years, the trees were 5 m tall and 8 cm in bole diameter, and after 20 years 8 m and 14 cm. In Madagascar the age of trees with a bole branchless for about 10 m and 50 cm in diameter has been estimated at 100 years. Young trees grow best under moderately shaded conditions. It may take a long time of about 30 years before trees start producing seeds. The seeds are dispersed by sea; they are frequently washed up on beaches.
Tests in Madagascar showed that the roots of Intsia bijuga develop a symbiosis with ectomycorrhizae.

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Ecology

In Madagascar Intsia bijuga is characteristic for undisturbed humid forest of the coastal zone of the eastern parts of the island, often also found behind beaches, usually below 50 m altitude. It occurs in regions with a mean annual rainfall of 2000–3000(–3500) mm, with up to 3 dry months, and a mean annual temperature of 24–27°C. It usually grows on well-drained, sandy soils with a pH of 4.7–5.3. Also elsewhere it occurs most frequently in coastal areas, often in a zone behind mangroves, but it is also found inland up to 600 m altitude. Intsia bijuga has some resistance to salt spray and saline soils and is quite resistant to wind. It does not tolerate longer periods of drought. It is frequently associated with Calophyllum chapelieri Drake, Hymenaea verrucosa Gaertn. and Uapaca thouarsii Baill., but sometimes it occurs in almost pure stands.

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Propagation and planting

In Papua New Guinea it has been observed that after logging dormant seeds in the soil germinate abundantly in the gaps around the stumps.
There are 180–250 seeds per kg. The seeds are protected by a hard seed coat, which is impermeable to water. Mature seeds have a moisture content of less than 10% and hence can survive for more than 3 years without any specific treatment. Germination may take up to nearly 2 years. To promote rapid and simultaneous germination, scarification followed by soaking in water is necessary. The most effective scarification technique is to use a file to scrape off the small protrusion of the seed coat (the strophiole) located at the opposite side of the hilum. Treatment with fungicides may protect scarified seeds from damage by fungi. Immersion in concentrated sulphuric acid for one hour is also effective in rupturing the seed coat. Seeds must be planted vertically with the hilum downward, so that the seed coat is shed as the hypocotyl emerges from the soil. Seed may be sown directly into the field. The germination rate of scarified seeds is 60–95% in a period of 3–20 weeks.
Seedlings need a high light intensity for optimal growth, and in the open growth is much faster than under closed canopy conditions. However, experiments in Indonesia showed that growth of seedlings under shelter or under shade trees was faster than in full sunlight. Appropriate drainage and high air humidity are important for good growth. Seedlings can be transplanted into the field when they are about 3 months old, at a spacing of 3 m × 4 m or 5 m × 5 m. In enrichment plantings in degraded forest in Madagascar, seeds have been sown at distances of 2 m × 1 m to 3.3 m × 3 m. Propagation by root suckers and cuttings is possible. Tests in tropical Asia with stem cuttings showed varying results, from low percentages of sprouting and rooting to 90% rooting.

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Management

In Madagascar natural stands of up to 80 exploitable trees per ha have been recorded, with a wood volume of 160 m³/ha. In Papua New Guinea a 50-year rotation for natural stands has been reported as suitable for Intsia spp., but in Malaysia it has been estimated that a rotation of some 120 years would be required for plantations.
In Madagascar it has been observed that young Intsia bijuga trees in enrichment plantings are very sensitive to soil and air humidity. They developed well in forest with a more or less constant humidity, but poorly when planted in more open conditions and they did not survive periods of drought. Seeds are sown in strips of 50 cm wide and 2 m apart, which have been cut open in the forest. These strips should be cleared every 2–3 years until the Intsia bijuga trees are 12–15 years old and reach the canopy of the forest. Thinning of the stands is needed once every 10 years.

Diseases and pests

Phellinus noxius, causing brown rot of roots and crown, is considered a threat to plantations. The roots of seedlings of Intsia bijuga may be infected by nematodes. In the Philippines Rotylenchulus sp. and Helicotylenchus sp. have been found in nurseries. In Indonesia young plantations suffered from grazing by deer, while rats are also considered a serious pest.
In Madagascar cylindrical protuberances up to 10 cm × 5 cm are commonly found on the bark of bole and larger branches, possibly caused by fungi.

Harvesting

Yield

In Madagascar trees with a free bole of 18 m long yielding 10 m³ of wood have been reported, but a wood volume of 2 m³ per tree is more common, of which about 1.2 m³ results after sawing as merchantable wood.

Handling after harvest

Fresh logs sink in water and must be transported over land.

Genetic resources and breeding

In the major merbau timber-producing countries, Intsia bijuga and other Intsia spp. are over-exploited, sometimes as a result of indiscriminate and illegal commercial logging. In 1992 Intsia spp. were proposed for inclusion in Appendix II of CITES. They were considered to merit conservation because stands have been exploited for many years for their hardwood which is popular in both domestic and international markets. However, the proposal was turned down. Intsia bijuga is included in the IUCN Red List of threatened species as vulnerable because of intensive exploitation.
In Madagascar Intsia bijuga is endangered because it has been much overexploited for its valuable timber. Remaining significant stands are few and restricted to protected and inaccessible localities along the eastern coast. Considerable variation has been reported in Intsia bijuga in Madagascar. Types with smaller leaves, fruits and seeds occur, but also the wood is variable, from yellowish and comparatively soft to reddish brown and hard. The wood variation may be influenced by environmental factors which affect the growth rate.

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Prospects

The market demand for Intsia timber is high for doors, window frames, parquet flooring, furniture and cabinet work. A significant portion of the production is for export, and various claims exist of illegal and unsustainable harvesting and illegal export. On a worldwide scale, there is an urgent need to regulate the harvest of Intsia timber. The prospects seem to depend on whether the exploitation of the remaining stands is properly controlled. This has already been brought to the attention of the international community. Merbau-producing species, including Intsia bijuga, have been suggested recently for inclusion in CITES Appendix III to obtain a better overview of trade data as a tool to ensuring sustainable management and trade.
It is evident that felling cycles should be long for these rather slow-growing trees; at least 60 years, though 80 years is probably more realistic. This means that a decrease in the amount of timber harvested is necessary in most areas. The often fair regeneration in logged-over areas and promising enrichment planting with nursery-raised seedlings offer possibilities for a fair supply of Intsia bijuga timber in the future. In Madagascar Intsia bijuga is well suited for enrichment planting in degraded forests in the high-rainfall regions in the coastal lowlands on sandy soils in the eastern parts of the island.

Major references

• Blaser, J., Rajoelison, G., Tsiza, G., Rajemison, M., Rabevohitra, R., Randrianjafy, H., Razafindrianilana, N., Rakotovao, G. & Comtet, S., 1993. Choix des essences pour la sylviculture à Madagascar. Akon’ny Ala: Bulletin du Département des Eaux et Forêts 12–13. 166 pp.
• Bolza, E. & Keating, W.G., 1972. African timbers: the properties, uses and characteristics of 700 species. Division of Building Research, CSIRO, Melbourne, Australia. 710 pp.
• CTFT (Centre Technique Forestier Tropical), 1951. Hintsy I. Fiche botanique et forestière. Bois et Forêts des Tropiques 18: 139–142.
• du Puy, D.J., Labat, J.N., Rabevohitra, R., Villiers, J.-F., Bosser, J. & Moat, J., 2002. The Leguminosae of Madagascar. Royal Botanic Gardens, Kew, Richmond, United Kingdom. 750 pp.
• Guéneau, P., Bedel, J. & Thiel, J., 1970–1975. Bois et essences malgaches. Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 150 pp.
• Johns, R.J., Laming, P.B., den Outer, R.W. & Sosef, M.S.M., 1993. Intsia Thouars. In: Soerianegara, I. & Lemmens, R.H.M.J. (Editors). Plant Resources of South-East Asia No 5(1). Timber trees: Major commercial timbers. Pudoc Scientific Publishers, Wageningen, Netherlands. pp. 264–270.
• Kiener, A., 1954. Note sur le Hintsy (Intsia bijuga O. Kze.). Bois et Forêts des Tropiques 38: 36–42.
• Orwa, C., Mutua, A., Kindt, R., Jamnadass, R. & Simons, A., 2009. Agroforestree database: a tree reference and selection guide. Version 4.0. [Internet] World Agroforestry Centre (ICRAF), Nairobi, Kenya. http://www.worldagroforestry.org/ resources/databases/ agroforestree. Accessed September 2011.
• Parant, B., Chichignoud, M. & Rakotovao, G., 1985. Présentation graphique des caractères technologiques des principaux bois tropicaux. Tome 5. Bois de Madagascar. CIRAD, Montpellier, France et Département des Recherches forestières et piscicoles du FOFIFA, Antananarivo, Madagascar. 161 pp.
• Tong, P.S., Chen, H.K., Hewitt, J. & Affre, A., 2009. Review of trade in merbau from major range states. TRAFFIC Southeast Asia, Petaling Jaya, Selangor, Malaysia. 128 pp.

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Other references

• Boiteau, P., Boiteau, M. & Allorge-Boiteau, L., 1999. Dictionnaire des noms malgaches de végétaux. 4 Volumes + Index des noms scientifiques avec leurs équivalents malgaches. Editions Alzieu, Grenoble, France.
• Brenan, J.P.M., 1967. Leguminosae, subfamily Caesalpinioideae. In: Milne-Redhead, E. & Polhill, R.M. (Editors). Flora of Tropical East Africa. Crown Agents for Oversea Governments and Administrations, London, United Kingdom. 230 pp.
• CAB International, 2010. Forestry Compendium. Intsia bijuga. [Internet] http://www.cabi.org/ fc/?compid=2&dsid=28750&loadmodule=datasheet&page=2147&site=163. Accessed September 2011.
• Fouquet, D., 1984. Etude comparative de bois commerciaux provenant de continents différents pouvant être confondus. Bois et Forêts des Tropiques 205: 35–59.
• Keong, C.H., 2006. Review of trade in merbau (Intsia spp.) from major range States to Germany and the EU: A preliminary assessment. TRAFFIC International, Petaling Jaya, Selangor, Malaysia. 9 pp.
• Sallenave, P., 1955. Propriétés physiques et mécaniques des bois tropicaux de l’Union française. Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 129 pp.
• Schatz, G.E., 2001. Generic tree flora of Madagascar. Royal Botanic Gardens, Kew, Richmond, United Kingdom. 477 pp.
• Takahashi, A., 1978. Compilation of data on the mechanical properties of foreign woods (part 3) Africa. Shimane University, Matsue, Japan. 248 pp.
• World Conservation Monitoring Centre, 1998. Intsia bijuga. In: IUCN. Red list of threatened species. Version 2011.1. [Internet] http://www.iucnredlist.org. Accessed September 2011.

Afriref references

Sources of illustration

• Brenan, J.P.M., 1967. Leguminosae, subfamily Caesalpinioideae. In: Milne-Redhead, E. & Polhill, R.M. (Editors). Flora of Tropical East Africa. Crown Agents for Oversea Governments and Administrations, London, United Kingdom. 230 pp.

Author(s)

•	A. Asamoah Kwame Nkrumah University of Science & Technology, Kumasi, Ghana
•	A. Atta-Boateng Kwame Nkrumah University of Science & Technology, Kumasi, Ghana
•	A. Sarfowaa Kwame Nkrumah University of Science & Technology, Kumasi, Ghana

Editors

•	R.H.M.J. Lemmens PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
•	D. Louppe CIRAD, Département Environnements et Sociétés, Cirad es-dir, Campus international de Baillarguet, TA C 105 / D (Bât. C, Bur. 113), 34398 Montpellier Cédex 5, France
•	A.A. Oteng-Amoako Forestry Research Institute of Ghana (FORIG), University P.O. Box 63, KNUST, Kumasi, Ghana

Associate editors

•	E.A. Obeng Forestry Research Institute of Ghana (FORIG), University P.O. Box 63, KNUST, Kumasi, Ghana

Photo editor

•	G.H. Schmelzer PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Correct citation of this article

Asamoah, A., Atta-Boateng, A. & Sarfowaa, A., 2012. Intsia bijuga (Colebr.) Kuntze. [Internet] Record from PROTA4U. Lemmens, R.H.M.J., Louppe, D. & Oteng-Amoako, A.A. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands. <http://www.prota4u.org/search.asp>. Accessed .

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