Difference between revisions of "Diospyros crassiflora (PROTA)"

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Plant Resources of Tropical Africa Introduction

List of species

General importance
Geographic coverage Africa
Geographic coverage World
Medicinal
Timber
Fuel
Conservation status

Diospyros crassiflora Hiern

Protologue: Monogr. Eben.: 260 (1873); Trans. Camb. Phil. Soc. 12: 260 (1873).

Family: Ebenaceae

Synonyms

Vernacular names

African ebony, West African ebony, Benin ebony (En). Ebène d’Afrique, ebène noir, ebénier véritable du Gabon (Fr).

Origin and geographic distribution

Diospyros crassiflora occurs from southern Nigeria east to the Central African Republic, and south to Gabon and DR Congo.

Uses

The black heartwood (traded from Cameroon as ‘mevini’, from Equatorial Guinea as ‘ébano’ and from Gabon as ‘evila’) is used for heavy flooring, interior trim, ship building, vehicle bodies, furniture, cabinet making, musical instruments (especially the black keys of pianos, but also guitar fingerboards), precision equipment, turnery, carvings, knife-handles and brush backs. The sapwood and sometimes also the heartwood is used for poles, posts, vehicle bodies, agricultural implements, toys, novelties, sporting goods, combs, ladders, boxes, crates, crossbows, veneer and plywood. The wood is also used as firewood.

In traditional medicine, a bark decoction is drunk and used as a wash to treat ovarian problems, and the bark powder is applied to heal sores and wounds. The leaf sap is applied as eye drops to treat eye inflammations. In Gabon the bark is used in a mixture with the heartwood of Pterocarpus soyauxii Taub. to treat yaws.

Production and international trade

The wood of Diospyros crassiflora is considered the true ebony of commerce from Africa and has been for a long time an important export product from Nigeria, Cameroon and Gabon. The total volumes exported from these countries are unknown, but are low at present because of dwindling stands. In the 1960s around 70 m³ of wood were exported annually from Cameroon and 56 m³ in 1972, and in 1960 Gabon exported 130 m³ and in 1994 35 m³. Currently, export and utilization of the wood requires special permission in Cameroon. DR Congo is considered the major exporter at present. The high-quality carvings are in great demand by tourists.

Properties

The heartwood is jet-black to black-brown or dark brown with black streaks. It is distinctly demarcated from the sapwood, which is pinkish to pale red after cutting darkening to pale reddish brown upon exposure, and up to 12 cm thick. The grain is straight, occasionally interlocked or curly, texture fine.

The wood is heavy with a density of 900–1010 kg/m³ at 12% moisture content. It air dries slowly, with high risks of distortion and checking, but in small dimensions it may dry fairly rapidly and with little degrade. The rates of shrinkage are high, from green to 12% moisture content about 5.5% radial and 6.5% tangential and from green to oven dry 7.0% radial and 11.0% tangential. Once dried, the wood is often poorly stable in service.

At 12% moisture content, the modulus of rupture is 130–179 N/mm², modulus of elasticity 15,500–18,900 N/mm², compression parallel to grain 58–88 N/mm², shear 17 N/mm, Janka side hardness 14,320 N and Monnin hardness 7.0.

The wood is difficult to saw and work, with serious dulling effect on saws and cutting edges. Stellite-tipped sawteeth and tungsten-carbide cutting tools are recommended, and powerful machines are needed for machining. The wood surfaces take an excellent polish, but picking up of interlocked or curly grain may occur in planing and a reduced cutting angle is recommended. The wood has a tendency to split upon nailing, and pre-boring is advised. It has good slicing properties, but powerful machines are needed. The gluing properties are satisfactory. A preliminary surface treatment with alcohol is recommended for coatings. The wood is moderately durable, being moderately resistant to termite attack, but susceptible to pinhole borers and marine borers attacks. It is extremely resistant to preservative treatment. Saw dust may cause allergic contact dermatitis in wood workers.

The stem bark showed significant in-vitro antibacterial and antifungal activities. Plumbagin, cyclocanaliculatin, gerberinol, lupeol, lupenone and betulinic acid have been isolated from the stem bark, and the naphthoquinone crassiflorone has also been isolated. Some of these compounds have also shown antibacterial and antifungal properties.

Adulterations and substitutes

The wood of Diospyros crassiflora is often mixed with that of other African Diospyros spp. with blackish heartwood such as Diospyros mespiliformis Hochst. ex A.DC. African blackwood (from Dalbergia melanoxylon Guill. & Perr.) resembles the wood of Diospyros crassiflora and is used for similar purposes.

Description

Dioecious medium-sized tree up to 25 m tall; bole cylindrical or fluted, branchless for up to 15 m, up to 120 cm in diameter, without buttresses; bark surface with fine longitudinal fissures, exfoliating in rather thick scales, blackish grey to black, inner bark black and brittle in outer layer, pale salmon pink with creamy streaks in inner layer; branches reddish grey-brown, with longitudinal cracks; young twigs glabrous. Leaves alternate, simple and entire; stipules absent; petiole up to 1.5 cm long, grooved above, nearly glabrous; blade lanceolate-elliptical to oblong-elliptical, 10–21 cm × 4–10 cm, cuneate to rounded and slightly asymmetrical at base, abruptly acuminate at apex, thin-leathery, nearly glabrous, glossy dark green above, paler below, pinnately veined with 5–8 pairs of lateral veins, finest veins perpendicular to lateral veins. Inflorescence an axillary fascicle, often on older branches, 3–6-flowered for male inflorescence, 1–2-flowered for female one. Flowers unisexual, regular, nearly sessile; calyx fleshy, up to 10 mm long, pinkish red, with tube slightly longer than the (4–)5 lobes; corolla 2.5–3 cm long, fleshy, short-hairy, pinkish white, with ellipsoid tube and 4–6 short lobes; male flowers with numerous stamens up to 1.5 cm long, with very short filaments, ovary rudimentary; female flowers with rudimentary stamens, ovary superior, globose, c. 5 mm in diameter, 8–10-celled, styles 4–5. Fruit an ellipsoid to obovoid berry, up to 10 cm × 6.5 cm, sparsely hairy to glabrous, yellowish when ripe, enclosed at base by enlarged calyx up to 4 cm in diameter, up to 10-seeded. Seeds oblong, up to 5 cm × 2 cm × 1.5 cm, glossy brown to black.

Other botanical information

Diospyros is a large pantropical genus of about 500 species; in tropical Africa about 90 species occur and several produce valuable timber or edible fruits.

Anatomy

Wood-anatomical description (IAWA hardwood codes):

Growth rings: 2: growth ring boundaries indistinct or absent. Vessels: 5: wood diffuse-porous; (10: vessels in radial multiples of 4 or more common); 13: simple perforation plates; 22: intervessel pits alternate; (23: shape of alternate pits polygonal); 25: intervessel pits small (4–7 μm); 30: vessel-ray pits with distinct borders; similar to intervessel pits in size and shape throughout the ray cell; 41: mean tangential diameter of vessel lumina 50–100 μm; 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; 70: fibres very thick-walled. Axial parenchyma: 77: axial parenchyma diffuse-in-aggregates; 78: axial parenchyma scanty paratracheal; 86: axial parenchyma in narrow bands or lines up to three cells wide; 87: axial parenchyma reticulate; 92: four (3–4) cells per parenchyma strand; 93: eight (5–8) cells per parenchyma strand. Rays: 96: rays exclusively uniseriate; 97: ray width 1–3 cells; 106: body ray cells procumbent with one row of upright and/or square marginal cells; 107: body ray cells procumbent with mostly 2–4 rows of upright and/or square marginal cells; 108: body ray cells procumbent with over 4 rows of upright and/or square marginal cells; (109: rays with procumbent, square and upright cells mixed throughout the ray); (113: disjunctive ray parenchyma cell walls present); 116: ≥ 12 rays per mm. Mineral inclusions: 136: prismatic crystals present; 142: prismatic crystals in chambered axial parenchyma cells.

(E.E. Mwakalukwa, P.E. Gasson & E.A. Wheeler)

Growth and development

Diospyros crassiflora is slow growing. In natural forest in Cameroon the mean diameter growth was 4.5 mm/year for trees with a mean height of 14.5 m and a mean age of 50 years. However, two trees measured over a period of 10 years in central Gabon had an average annual growth rate of only 1 mm in diameter. In a 50-years-old plantation in Cameroon, dominant trees were on average 24 m tall and 22 cm in bole diameter, whereas the standing volume was estimated at 320 m³/ha.

In Cameroon flowering of trees has been recorded from February to May, in Gabon from September to October. Fruits ripen about 6 months later. They are eaten by animals, which probably serve as seed dispersers.

Ecology

Diospyros crassiflora occurs in lowland semi-deciduous and evergreen forest up to 1000 m altitude, but usually avoids the most humid forest types.

Management

Diospyros crassiflora is in general uncommon in the forest, usually occurring as isolated trees or in small groups of 2–3. In western Cameroon the average wood volume of boles of more than 15 cm diameter was recorded as 0.25 m³/ha. Trees coppice well.

Diseases and pests

In Cameroon attacks of jumping plant-lice and other leaf-defoliating insects on Diospyros crassiflora have been recorded.

Harvesting

Trees are harvested by the selective logging system. Some caution is needed during harvesting operations because logs may have brittle heart. In Gabon and the Central African Republic the minimum bole diameter allowed for felling is 40 cm, in DR Congo and Cameroon 60 cm.

Handling after harvest

Due to the high density of the wood logs do not float in water and cannot be transported by river.

Genetic resources

Nearly all big trees of Diospyros crassiflora have been heavily overexploited with few remaining stands in the most remote areas of its range, and the species seems to have poor natural regeneration. Therefore, Diospyros crassiflora is classified as endangered in the IUCN Red List of threatened species.

Prospects

In spite of the fact that Diospyros crassiflora is highly demanded for its commercial ebony wood, very little research has been carried out on its propagation and management in natural forest. Therefore, requirements for sustainable exploitation are still unclear, but the long time needed for the production of black heartwood of sufficient diameter to be interesting for the timber market and the scarcity of large trees seem to preclude sustainable commercial exploitation. More research is recommended in natural regeneration measures to protect the species.

Major references

• 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.

• Burkill, H.M., 1994. The useful plants of West Tropical Africa. 2nd Edition. Volume 2, Families E–I. Royal Botanic Gardens, Kew, Richmond, United Kingdom. 636 pp.

• Dalziel, J.M., 1937. The useful plants of West Tropical Africa. Crown Agents for Overseas Governments and Administrations, London, United Kingdom. 612 pp.

• Dzoyem, J.P., Tangmouo, J.G., Kechia, F.A., Lontsi, D., Etoa, F.X. & Lohoue, P.J., 2006. In vitro antidermatophytic activity of Diospyros crassiflora Hiern [Ebenaceae]. Sudanese Journal of Dermatology 4(1): 10–15.

• Keay, R.W.J., 1989. Trees of Nigeria. A revised version of Nigerian trees (1960, 1964) by Keay, R.W.J., Onochie, C.F.A. & Stanfield, D.P. Clarendon Press, Oxford, United Kingdom. 476 pp.

• Kennedy, D.J., 1936. Forest flora of southern Nigeria. Government Printer, Lagos, Nigeria. 277 pp.

• Letouzey, R. & White, F., 1970. Ebenaceae. Flore du Gabon. Volume 18. Muséum National d’Histoire Naturelle, Paris, France. 189 pp.

• Neuwinger, H.D., 2000. African traditional medicine: a dictionary of plant use and applications. Medpharm Scientific, Stuttgart, Germany. 589 pp.

• White, F., 1978. The taxonomy, ecology and chorology of African Ebenaceae I. The Guineo Congolian species. Bulletin du Jardin Botanique National de Belgique 48: 245–358.

• White, F., 1987. Ebenaceae. In: Bamps, P. (Editor). Flore d’Afrique centrale. Spermatophytes. Jardin botanique national de Belgique, Brussels, Belgium. 103 pp.

Other references

• African Regional Workshop (Conservation & Sustainable Management of Trees, Zimbabwe), 1998. Diospyros crassiflora. In: IUCN. 2009 IUCN Red list of threatened species. Version 2009.1. [Internet] http://www.iucnredlist.org. October 2009.

• ATIBT (Association Technique Internationale des Bois Tropicaux), 1986. Tropical timber atlas: Part 1 – Africa. ATIBT, Paris, France. 208 pp.

• Burkhardt, D. & Lebel, J., undated. Taxonomy and biology of jumping plant-lice (Hemiptera: Psylloidea) of Cameroon, including pests of cultivated plants and forest timber and strategies for an integrated pest management. [Internet] http://www.kfpe.ch/ projects/rpdc/ burkhardt.php. October 2009.

• CIRAD Forestry Department, 2009. Ebène d’Afrique. [Internet] Tropix 6.0. http://tropix.cirad.fr/ africa/ebene.pdf. October 2009.

• Foahom, B., 2003. Preliminary investigations on insect pest attacks in a disturbed evergreen forest of south Cameroon. International Forestry Review 6(2): 195–200.

• Maisonneuve, J.F. & Manfredini, M.L. (Editors), 1988. Ebène. Les bois du Gabon. Département de Sciences Naturelles, Institut Pédagogique National, Ministère de l’éducation nationale, Libreville, Gabon. pp. 68–69.

• Meier, E., 2009. The wood database: Gaboon Ebony. [Internet] http://www.wood-database.com/ lumber-identification/hardwoods/ gaboon-ebony. October 2009.

• Owona Ndongo, P.A., Peltier, R., Linjouom, I., Louppe, D., Smektala, G., Beligné, V., Njoukam, R., Tieche, R. & Temgoua, L., 2009. Plantations de bois d’oeuvre en zone équatoriale africaine: cas de l’arboretum de l’Enef de Mbalmayo au sud du Cameroun. Bois et Forêts des Tropiques 299: 37–48.

• Raponda-Walker, A. & Sillans, R., 1961. Les plantes utiles du Gabon. Paul Lechevalier, Paris, France. 614 pp.

• Widodo, S.H., 2001. Crescentia L. In: van Valkenburg, J.L.C.H. & Bunyapraphatsara, N. (Editors). Plant Resources of South-East Asia No 12(2): Medicinal and poisonous plants 2. Backhuys Publishers, Leiden, Netherlands. pp. 191–194.

• UNEP-WCMC, 2006. Contribution to an evaluation of tree species using the new CITES Listing Criteria. UNEP World Conservation Monitoring Centre, Cambridge, United Kingdom. [Internet]. http://www.unep-wcmc.org/ species/tree_study/pdfs/ 1.pdf. October 2009.

• Vivien, J. & Faure, J.J., 1985. Arbres des forêts denses d’Afrique Centrale. Agence de Coopération Culturelle et Technique, Paris, France. 565 pp.

• White, F., 1963. Ebenaceae. In: Hepper, F.N. (Editor). Flora of West Tropical Africa. Volume 2. 2nd Edition. Crown Agents for Oversea Governments and Administrations, London, United Kingdom. pp. 2–15.

• 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.

• Wilks, C. & Issembé, Y., 2000. Les arbres de la Guinée Equatoriale: Guide pratique d’identification: région continentale. Projet CUREF, Bata, Guinée Equatoriale. 546 pp.

• Worbes, M., Staschel, R., Roloff, A. & Junk, W.J., 2003. Tree ring analysis reveals age structure, dynamics and wood production of a natural forest stand in Cameroon. Forest Ecology and Management 173: 105–123.

Sources of illustration

• Vivien, J. & Faure, J.J., 1985. Arbres des forêts denses d’Afrique Centrale. Agence de Coopération Culturelle et Technique, Paris, France. 565 pp.

• White, F., 1987. Ebenaceae. In: Bamps, P. (Editor). Flore d’Afrique centrale. Spermatophytes. Jardin botanique national de Belgique, Brussels, Belgium. 103 pp.

Author(s)

• E.A. Obeng

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

Correct citation of this article

Obeng, E.A., 2010. Diospyros crassiflora Hiern. [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 23 December 2024.

• See the Prota4U database.