Afzelia bella (PROTA)

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Plant Resources of Tropical Africa
Introduction
List of species


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distribution in Africa (wild)
1, leaf; 2, inflorescence; 3, dehisced fruit. Redrawn and adapted by Iskak Syamsudin
base of bole
slash
flowering branch
flowers
flowers
flowers
seedling
wood in transverse section
wood in tangential section
wood in radial section

Afzelia bella Harms


Protologue: Bot. Jahrb. Syst. 49: 425 (1913).
Family: Caesalpiniaceae (Leguminosae - Caesalpinioideae)
Chromosome number: 2n = 24

Vernacular names

  • Afzelia (En).
  • Doussié, azodau (Fr).

Origin and geographic distribution

Afzelia bella is widespread, occurring from eastern Guinea and Liberia east to the Central African Republic, and south to DR Congo and Cabinda (Angola).

Uses

Like other Afzelia spp., the wood of Afzelia bella is characterized by an excellent stability with little susceptibility to variations in humidity, small shrinkage rates during drying and a good natural durability. The wood is durable and treatment with preservatives is unnecessary, even for usage in permanent humid conditions or in localities where wood-attacking insects are abundant. This makes it an excellent wood for use in pleasure-crafts, especially for keels, stems and panels, for bridges, as well as interior fittings. For such uses it is sometimes as much in demand as teak. The wood is also valued for joinery and panelling, both interior and exterior, parquet floors, doors, frames, stairs, vehicle bodies, furniture, sporting goods, mine props, musical instruments, railway sleepers, agricultural implements, utensils, tool handles, turnery, fibre board and particle board. It is suitable for decorative sliced veneer. Because of its good resistance to many chemical products and great dimensional stability, it is often preferred to materials like metals and synthetics for vats and precision equipment in industrial applications. The neutral pH of the wood makes it suitable for applications in contact with vulnerable objects such as antiques and old books in libraries. However, it should not be used in contact with textiles under more humid conditions because of the presence of colorants. The wood is also used as firewood and for charcoal production.

The leaves are sometimes eaten cooked as a vegetable. Livestock browses on the foliage. The seed aril is edible and reportedly sweet. Bark and sometimes roots and leaves are used in traditional medicine. Bark decoctions and macerations are taken to treat intestinal parasites, diarrhoea, menstruation problems, haemorrhoids and rheumatism, and as tonic. Ground bark is applied externally against skin diseases. Leaves are administered against constipation. The tree is decorative and sometimes planted as ornamental shade tree.

Production and international trade

Afzelia bella is not the most important Afzelia species for the international timber market. Its wood is often mixed with that of more commonly traded species such as Afzelia bipindensis Harms and Afzelia pachyloba Harms, and traded as ‘doussié’, for which Cameroon is the main exporting country. In 2003 Cameroon exported 9900 m³ of sawn doussié wood and 47,750 m³ in 2005. However, the share of Afzelia bella in these amounts was probably small because it is usually a small-sized tree in Central Africa. Exports from Côte d’Ivoire declined strongly in 2007 and 2008 because of dwindling stands and the economic crisis in importing countries. In 2005 Ghana exported 9000 m³ of sawn Afzelia wood (as ‘papao’), and 7000 m³ in 2006 at an average price of US$ 780 per m³.

Properties

The heartwood is orange-brown to golden brown, becoming red-brown upon prolonged exposure, sometimes with darker streaks. It is distinctly demarcated from the whitish to pale yellow, up to 8 cm wide sapwood. The grain is straight to interlocked, texture medium to coarse but even. The wood is slightly glossy and dried wood has a leather-like smell upon planing.

The wood is medium-weight to fairly heavy, with a density of 700–840 kg/m³ at 12% moisture content. Drying usually does not cause problems, without deformation and splitting, but the wood dries rather slowly. For thick boards (more than 7.5 cm), preliminary air drying under cover is recommended before kiln drying. The shrinkage rates are low, from green to oven dry 3.1% radial and 5.5% tangential. Once dry, the wood is very stable in service.

At 12% moisture content, the modulus of rupture is 90 N/mm², modulus of elasticity 12,500 N/mm², compression parallel to grain 60–85 N/mm², shear 6.5 N/mm², cleavage 17 N/mm, Janka side hardness 6000 N and Chalais-Meudon side hardness 4.3.

The wood saws easily when good equipment is used; it contains little silica (less than 0.015%) and stellite-tipped saw teeth are not needed for sawing fresh wood. Some logs have gum pockets, which may cause problems in sawing by blunting saw teeth. Tungsten-carbide-tipped cutting tools are recommended in planing and moulding operations. It is advisable to reduce the cutting angle to 15° to avoid rough surfaces when interlocked grain is present. The use of a filler is recommended to obtain smooth surfaces. The nailing and screwing properties are satisfactory, but pre-boring is recommended to avoid splitting. Gluing usually does not cause problems. The wood paints and varnishes well, but wood zones close to the centre of the log may contain anti-oxidant substances that slow down drying of varnish and may cause problems in painting. Sliced veneer of good quality can be produced, but the wood is not suitable for peeling. The wood has a good reputation for its resistance to acids and alkalines.

The heartwood is durable, with an excellent resistance to fungal, termite and borer attacks, but it is liable to marine borers. The sapwood is susceptible to Lyctus attack. The heartwood is resistant to impregnation with preservatives. Saw dust may cause allergic reactions, irritation of mucous membranes and asthma in wood workers.

Logs may have crevices filled with a whitish powdery substance originating from the wood vessels; the substance consists of kaempferol and derivatives. Kaempferol and its glycosides have antibacterial, antifungal and anti-inflammatory activities. These compounds have also been isolated from the bark together with other flavonoids and glycosides.

Although anti-nutritive and toxic compounds have been reported for the leaves, the foliage can be used as fodder because the level of these compounds is low. After a test of rumen degradation by goats, the foliage of Afzelia bella was even ranked as high-quality forage. The seeds contain about 7% water, 13% protein, 54% carbohydrate, 23% lipid and 3% ash. The energy value is 2190 kJ per 100 g. The seed oil contains crepenynic acid and dehydrocrepenynic acid. Crepenynic acid is a potential inhibitor of essential fatty acid metabolism, and proved toxic to sheep. Dehydrocrepenynic acid acts as inhibitor of conjugation in gram-negative bacteria, which may provide a means to control the spread of antibiotic resistance.

Adulterations and substitutes

The wood of three other Afzelia species is similar to that of Afzelia bella and also traded as ‘doussié’: Afzelia africana Sm. ex Pers., mainly exported from West Africa, and Afzelia bipindensis Harms and Afzelia pachyloba Harms, mainly exported from Central Africa. The excellent properties of Afzelia bella wood concerning dimensional stability and high natural durability are comparable to some well-known timbers such as merbau (Intsia spp.) and teak (Tectona grandis L.f.), and to the African makore (Tieghemella heckelii (A.Chev.) Roberty) and douka (Tieghemella africana Pierre).

Description

  • Evergreen or deciduous shrub or small to medium-sized tree up to 25(–35) m tall; bole straight and cylindrical or irregular, up to 100(–150) cm in diameter, often with unequal, small buttresses; bark surface brown to orange-brown, superficially scaly, with hoops or plate-sized scars of swirly concentric rings, inner bark granular, yellowish to pinkish, with gritty orange streaks, with yellowish brown exudate, aromatic; crown elongate to rounded or flattened depending on age and growing conditions, with tortuous, more or less upright branches; twigs slightly hairy to glabrous.
  • Leaves alternate, paripinnately compound with 3–6 pairs of leaflets; stipules with basal parts fused and persistent, upper parts free, linear and caducous; petiole and rachis together 6–18 cm long; petiolules 1–6 mm long, often slightly twisted; leaflets opposite, elliptical to elliptical-lanceolate, 4–16 cm × 1.5–7 cm, obtuse to short-acuminate at apex, usually glabrous, pinnately veined with 7–13 pairs of lateral veins.
  • Inflorescence a terminal or axillary panicle up to 25 cm long, usually short-hairy.
  • Flowers bisexual, zygomorphic, sweet-scented; pedicel 0.5–1 cm long; bracteoles c. 0.5 cm × 0.5 cm, caducous; hypanthium 1–2.5 cm long; sepals 4, 1–2.5 cm long, densely short-hairy; petal 1, 4–6 cm long, with long claw, 2-lobed, white to pink with red marking in the centre; fertile stamens 7 and 3–4 cm long, rudimentary stamens 2 and c. 1.5 cm long; ovary superior, c. 1 cm long, with short stipe, slightly hairy, style c. 4.5 cm long.
  • Fruit a kidney-shaped, flattened pod 10–12 cm × 4–5 cm, dark brown to black, dehiscing with 2 woody valves, (1–)3–15-seeded.
  • Seeds ellipsoid or oblong-ellipsoid, 2–3 cm long, black, with 2-lobed, orange to red aril covering the seed for c. 2/3.
  • Seedling with epigeal germination; hypocotyl 6–11 cm long, epicotyl 8–12 cm long, glabrous; cotyledons fleshy, oblong, 2–3 cm long, erect; first 2 leaves opposite, with 3 pairs of leaflets.

Other botanical information

Afzelia comprises about 11 species, 7 of which occur in tropical Africa and 4 in South-East Asia. It is closely related to Intsia.

Three varieties have been distinguished in Afzelia bella: var. graciolor Keay, occurring from Côte d’Ivoire to Ghana and becoming a medium-sized tree with comparatively small leaflets and flowers; var. bella, occurring from Nigeria to DR Congo and Cabinda (Angola), an understorey shrub or small tree up to 12 m tall, rarely taller; and var. glabra Aubrév. from Congo with glabrous inflorescences.

Afzelia bella is close to Afzelia bipindensis Harms, which is usually a much bigger tree. However, in Côte d’Ivoire and Ghana (where Afzelia bipindensis does not occur) Afzelia bella can also reach large dimensions.

Afzelia parviflora

Afzelia parviflora (Vahl) Hepper (synonym: Afzelia bracteata Vogel ex Benth.) occurs in Guinea, Sierra Leone, Liberia and western Côte d’Ivoire, in evergreen and moist semi-deciduous forest, often along rivers. It differs from Afzelia bella in its leaflets, which are usually more rounded at apex, in its larger, more or less persistent bracts (small and early deciduous in Afzelia bella), and in its petal, which is carmine red inside. Afzelia parviflora is a small to medium-sized tree up to 30(–35) m tall with bole up to 50(–100) cm in diameter. Its wood is similar to that of Afzelia bella, with a density of about 790 kg/m³ at 12% moisture content, and is used for similar purposes, and traditionally for canoes. The bark is used in traditional medicine to treat onchocerciasis. Pounded seeds are reportedly an ingredient of soup.

Anatomy

Wood-anatomical description (IAWA hardwood codes):

  • Growth rings: 1: growth ring boundaries distinct.
  • Vessels: 5: wood diffuse-porous; 13: simple perforation plates; 22: intervessel pits alternate; 23: shape of alternate pits polygonal; 26: intervessel pits medium (7–10 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; 47: 5–20 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; 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.
(N.P. Mollel, P. Baas & H. Beeckman)

Growth and development

The growth of Afzelia bella is slightly slower than that of Afzelia africana. In plantations on cleared sites in evergreen forest in Côte d’Ivoire, the average height of trees was 13–15 m 17 years after planting, with a mean bole diameter of 15.5–19 cm. In Côte d’Ivoire trees flower in October–December and fruits mature in December–March. In Ghana trees flower in the dry season, before losing their leaves and ripe fruits develop towards the end of the dry season. The roots are associated with ectomycorrhizal fungi.

Ecology

In Côte d’Ivoire and Ghana, Afzelia bella usually occurs in moister forest types, in evergreen as well as moist semi-deciduous forest. It is often found on slopes and in slightly swampy localities. In Cameroon, Gabon and DR Congo Afzelia bella occurs as understorey shrub or small tree in primary as well as secondary forest on well-drained localities.

Propagation and planting

Natural regeneration of Afzelia bella is usually in the shade. There are 600–700 seeds per kg. The germination rate of fresh seed is high, and germination starts 1–3 weeks after sowing. Tests in Côte d’Ivoire showed a high mortality in planted seedlings, up to 70%.

Management

Afzelia bella usually occurs scattered, rarely in small groups.

Harvesting

The minimum bole diameter for harvesting is 50 cm in Côte d’Ivoire, 70 cm in Gabon and 80 cm in the Central African Republic.

Handling after harvest

Prolonged stocking of logs after harvesting does not cause problems except occasional black holes in the sapwood caused by borer attacks. Logs of Afzelia bella are too heavy to be transported by river.

Genetic resources

Afzelia bella is not threatened by genetic erosion because it occurs widespread and is locally common, particularly in Central Africa. Moreover, it is not exploited on a large scale. The large variation in the size of the trees, with seemingly regional differences, is remarkable. Differences in wood properties between provenances have also been recorded.

Prospects

Afzelia bella may have prospects as a commercial plantation timber, although it does not grow rapidly. The high value of its wood makes it economically interesting. The large variation in tree habit and size, and in wood properties warrant research on its genetic diversity and breeding for superior characteristics.

The seeds may be a useful nutrient source for humans and animals, but further toxicological studies are needed. Pharmacological studies are needed to support the uses in traditional medicine. The tree has ornamental value.

Major references

  • Amartey, S., Huang, Z. & Attah, A., 2004. Alternative timbers to Iroko (Milicia excelsa) for various end-uses: Ghana’s offer. Paper prepared for the 35th Annual Meeting, International Research Group on Wood Preservation, 6–10 June 2004, Ljubljana, Slovenia. 7 pp.
  • ATIBT (Association Technique Internationale des Bois Tropicaux), 1986. Tropical timber atlas: Part 1 – Africa. ATIBT, Paris, France. 208 pp.
  • Aubréville, A., 1959. La flore forestière de la Côte d’Ivoire. Deuxième édition révisée. Tome premier. Publication No 15. Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 369 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.
  • CIRAD Forestry Department, 2009. Doussie. [Internet] Tropix 6.0. http://tropix.cirad.fr/ africa/ doussie.pdf. January 2011.
  • CTFT (Centre Technique Forestier Tropical), 1980. Doussié. Bois et Forêts des Tropiques 189: 37–54.
  • de Koning, J., 1983. La forêt de Banco. Part 2: La Flore. Mededelingen Landbouwhogeschool Wageningen 83–1. Wageningen, Netherlands. 921 pp.
  • Gérard, J., Edi Kouassi, A., Daigremont, C., Détienne, P., Fouquet, D. & Vernay, M., 1998. Synthèse sur les caractéristiques technologiques des principaux bois commerciaux africains. Document Forafri 11. Cirad, Montpellier, France. 185 pp.
  • Hawthorne, W. & Jongkind, C., 2006. Woody plants of western African forests: a guide to the forest trees, shrubs and lianes from Senegal to Ghana. Kew Publishing, Royal Botanic Gardens, Kew, United Kingdom. 1023 pp.
  • Sallenave, P., 1964. Propriétés physiques et mécaniques des bois tropicaux. Premier supplément. Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 79 pp.

Other references

  • Aké Assi, L., Abeye, J., Guinko, S., Riguet, R. & Bangavou, X., 1985. Médecine traditionnelle et pharmacopée - Contribution aux études ethnobotaniques et floristiques en République Centrafricaine. Agence de Coopération Culturelle et Technique, Paris, France. 140 pp.
  • Aubréville, A., 1968. Légumineuses - Caesalpinioidées (Leguminosae - Caesalpinioideae). Flore du Gabon. Volume 15. Muséum National d’Histoire Naturelle, Paris, France. 362 pp.
  • Aubréville, A., 1970. Légumineuses - Césalpinioidées (Leguminosae - Caesalpinioideae). Flore du Cameroun. Volume 9. Muséum National d’Histoire Naturelle, Paris, France. 339 pp.
  • Burkill, H.M., 1995. The useful plants of West Tropical Africa. 2nd Edition. Volume 3, Families J–L. Royal Botanic Gardens, Kew, Richmond, United Kingdom. 857 pp.
  • Chudnoff, M., 1980. Tropical timbers of the world. USDA Forest Service, Agricultural Handbook No 607, Washington D.C., United States. 826 pp.
  • de la Mensbruge, G., 1966. La germination et les plantules des essences arborées de la forêt dense humide de la Côte d’Ivoire. Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 389 pp.
  • Ezeagu, I.E., Metges, C.C., Proll, J., Petzke, K. & Akinsoyinu, A.O., 1996. Chemical composition and nutritive value of some wild-gathered tropical plant seeds. Food and Nutrition Bulletin 17(3): 275–278.
  • Hausen, B.M., 1981. Woods injurious to human health: a manual. Walter de Gruyter & Co., Berlin, Germany. 189 pp.
  • Hawthorne, W.D., 1995. Ecological profiles of Ghanaian forest trees. Tropical Forestry Papers 29. Oxford Forestry Institute, Department of Plant Sciences, University of Oxford, United Kingdom. 345 pp.
  • Koch, G., Richter, H.G. & Schmitt, U., 2006. Topochemical investigation on phenolic deposits in the vessels of afzelia (Afzelia spp.) and merbau (Intsia spp.) heartwood. Holzforschung 60: 583–588.
  • Neuwinger, H.D., 2000. African traditional medicine: a dictionary of plant use and applications. Medpharm Scientific, Stuttgart, Germany. 589 pp.
  • Normand, D., 1950. Atlas des bois de la Côte d’Ivoire. Tome 1. Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 148 pp.
  • Normand, D. & Paquis, J., 1976. Manuel d’identification des bois commerciaux. Tome 2. Afrique guinéo-congolaise. Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 335 pp.
  • Oteng-Amoako, A.A. (Editor), 2006. 100 tropical African timber trees from Ghana: tree description and wood identification with notes on distribution, ecology, silviculture, ethnobotany and wood uses. 304 pp.
  • Raponda-Walker, A. & Sillans, R., 1961. Les plantes utiles du Gabon. Paul Lechevalier, Paris, France. 614 pp.
  • Takahashi, A., 1978. Compilation of data on the mechanical properties of foreign woods (part 3) Africa. Shimane University, Matsue, Japan. 248 pp.
  • Ubani, O.N., Tewe, O.O. & Smith, J., 2004. Rumen dry matter degradation of tree species by West African dwarf goats. Tropical Science 44(1): 6–8.
  • Voorhoeve, A.G., 1979. Liberian high forest trees. A systematic botanical study of the 75 most important or frequent high forest trees, with reference to numerous related species. Agricultural Research Reports 652, 2nd Impression. Centre for Agricultural Publishing and Documentation, Wageningen, Netherlands. 416 pp.
  • White, L. & Abernethy, K., 1997. A guide to the vegetation of the Lopé Reserve, Gabon. 2nd edition. Wildlife Conservation Society, New York, United States. 224 pp.
  • Wilczek, R., Léonard, J., Hauman, L., Hoyle, A.C., Steyaert, R., Gilbert, G. & Boutique, R., 1952. Caesalpiniaceae. In: Robyns, W., Staner, P., Demaret, F., Germain, R., Gilbert, G., Hauman, L., Homès, M., Jurion, F., Lebrun, J., Vanden Abeele, M. & Boutique, R. (Editors). Flore du Congo belge et du Ruanda-Urundi. Spermatophytes. Volume 3. Institut National pour l’Étude Agronomique du Congo belge, Brussels, Belgium. pp. 234–554.

Sources of illustration

  • Aubréville, A., 1970. Légumineuses - Césalpinioidées (Leguminosae - Caesalpinioideae). Flore du Cameroun. Volume 9. Muséum National d’Histoire Naturelle, Paris, France. 339 pp.
  • Hawthorne, W. & Jongkind, C., 2006. Woody plants of western African forests: a guide to the forest trees, shrubs and lianes from Senegal to Ghana. Kew Publishing, Royal Botanic Gardens, Kew, United Kingdom. 1023 pp.

Author(s)

  • J. Gérard, UPR Production et valorisation des bois tropicaux et méditerranéens, 73 rue Jean-François Breton, TA B-40 / 16 (Bât. 16, Bur. 123), 34398 Montpellier Cédex 5, France
  • 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

Correct citation of this article

Gérard, J. & Louppe, D., 2011. Afzelia bella Harms. In: 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. Accessed 14 April 2019.