Bikinia coriacea (PROTA)

Plant Resources of Tropical Africa Introduction

List of species

General importance
Geographic coverage Africa
Geographic coverage World
Timber
Conservation status

distribution in Africa (wild)

1, base of bole; 2, twig with flower buds; 3, fruit. Redrawn and adapted by Iskak Syamsudin

Bikinia coriacea (J.Morel ex Aubrév.) Wieringa

Protologue: Wageningen Agric. Univ. Pap. 99(4): 204 (1999).

Family: Caesalpiniaceae (Leguminosae - Caesalpinioideae)

Synonyms

• Monopetalanthus coriaceus J.Morel ex Aubrév. (1968).

Vernacular names

• Andoung de Morel (Fr).

Origin and geographic distribution

Bikinia coriacea has a very small area of distribution, being endemic to north-western Gabon and possibly also occurring in central Gabon.

Uses

The wood, traded from Gabon as ‘andoung’ together with other Bikinia spp., Aphanocalyx spp. and some other Caesalpiniaceae, is used for light construction, joinery, furniture, vehicle bodies, ladders, sporting goods, toys, novelties, tool handles, boxes, crates, matches, veneer, plywood and pulpwood. It is also suitable for light flooring, interior trim, ship building and railway sleepers.

Production and international trade

The export of ‘andoung’ logs from Gabon increased from 2700 m³ in 1991 to 47,000 m³ in 1999. However, the contribution of Bikinia coriacea was probably small because of its limited area of distribution. At present, the export of ‘andoung’ timber from Gabon seems insignificant.

Properties

The heartwood is pale pinkish brown with small stripes, darkening upon exposure, and not distinctly demarcated from the up to 12.5 cm wide sapwood. The grain is interlocked, texture fine and even.

The wood is medium-weight, with a density of 530–670 kg/m³ at 12% moisture content, and rather soft but tough. It air dries fairly well with little degrade, but some care is needed. The rates of shrinkage are moderate to rather high, from green to oven dry 3.7–4.5% radial and 7.1–9.5% tangential. Once dry, the wood is stable in service.

At 12% moisture content, the modulus of rupture is 109–163 N/mm², modulus of elasticity 8240–13,630 N/mm², compression parallel to grain 48–55 N/mm², shear 5–10.5 N/mm², cleavage 13–20 N/mm and Chalais-Meudon side hardness 2.1–4.1.

The wood works well with both machine and hand tools. In planing operations rough patches may occur due to the interlocked grain. The wood holds screws and nails well. Gluing properties are good and the wood paints well and takes a satisfactory finish. Boring and peeling characteristics are good. The wood is moderately durable, being quite resistant to termite attack, but susceptible to pinhole borer and Lyctus attacks. The heartwood is resistant to impregnation with preservatives, but the sapwood is permeable.

Description

• Large tree up to 53 m tall; bole straight, cylindrical, branchless for up to 26 m, up to 100(–120) cm in diameter, with buttresses up to 2 m high; bark surface smooth to fissured, greyish brown with reddish brown lenticels, inner bark fibrous, orange-brown; crown hemispherical; twigs greyish brown with brown lenticels, yellowish brown hairy.
• Leaves arranged spirally, paripinnately compound with 19–36 pairs of leaflets; stipules free, obovate, up to 7 cm long, early caducous leaving annular scars on twigs; petiole 2–7 mm long, rachis up to 20 cm long, slightly grooved above; leaflets opposite, sessile, narrowly oblong to linear, asymmetrical, 0.5–5 cm × 0.1–0.8 cm, leathery, glabrous.
• Inflorescence an axillary compound raceme 3–8 cm long, brown short-hairy, with up to 6 lateral branches up to 1.5 cm long; bracts up to 1 cm long.
• Flowers bisexual or male, zygomorphic, scented, at base with 2 ovate bracteoles up to 8 mm long; pedicel 0.5–4 mm long, hairy; sepals 5, small, up to 1 mm long, 2 fused into a 2-lobed band; petals 3–5, white, one up to 6 mm long, others up to 1 mm long; stamens 10, 9 fused at base, 1 free, anthers purplish; ovary superior, with c. 2 mm long stipe, hairy, 1-celled, style c. 5 mm long, hairy at base; male flowers with reduced ovary.
• Fruit an obovate, flat pod 10–14 cm × 4–6 cm, with 0.5–1 cm long stipe, short-pointed at apex, narrowly winged at upper suture, with a longitudinal vein near the middle of the lateral sides, 1–2-seeded.
• Seeds lens-shaped, c. 3 cm long, with very thin seed coat.
• Seedling with epigeal germination; hypocotyl 6–8.5 cm long, epicotyl 15–19 cm long; first two leaves opposite, with 14–16 pairs of leaflets, subsequent leaves alternate.

Other botanical information

Bikinia comprises 10 species and is confined to rainforest and gallery forest of western Central Africa. It is most closely related to Aphanocalyx and Tetraberlinia.

Anatomy

Wood-anatomical description (IAWA hardwood codes):

• Growth rings: (1: growth ring boundaries distinct); 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)); 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: 79: axial parenchyma vasicentric; 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: 96: rays exclusively uniseriate; (97: ray width 1–3 cells); 104: all ray cells procumbent; 106: body ray cells procumbent with one row of upright and/or square marginal cells; 113: disjunctive ray parenchyma cell walls present; 115: 4–12 rays per mm.
• Mineral inclusions: 136: prismatic crystals present; 142: prismatic crystals in chambered axial parenchyma cells.

(E. Ebanyenle, P. Baas & H. Beeckman)

Growth and development

An average annual growth rate of 2 cm in bole diameter has been estimated for a 47-years-old tree with a bole diameter of 105 cm in an arboretum in Gabon.

Flowering trees have been recorded in July and October. Pollination is probably by insects such as bees, flies, butterflies and moths, and perhaps also by sunbirds. The seeds, having a very thin seed coat, are susceptible to desiccation, which necessitates immediate germination after seed shedding. Seedlings probably need ectomycorrhizal fungi for proper growth.

Ecology

Bikinia coriacea occurs in dryland rainforest up to 300 m altitude. It usually occurs scattered in the forest, but important stands have been reported in some regions in north-western Gabon.

Handling after harvest

Logs are susceptible to insect and fungal attacks after felling; they should be removed from the forest as soon as possible or treated with preservatives. Fresh logs float in water and thus can be transported by river.

Genetic resources

Bikinia coriacea may become threatened by genetic erosion because it has a small distribution area. It does not seem to be logged much at present, but more intensified logging operations in the future might easily endanger this species.

Prospects

Bikinia coriacea provides wood of good quality, and, like some other Bikinia spp., it may have good prospects for planting in timber plantations because it seems to grow quite rapidly into large, straight and cylindrical boles, even on poor soils. However, much research is still needed, especially on propagation and growth in relation to mycorrhizal relationships.

Major references

• Aubréville, A., 1968. Légumineuses - Caesalpinioidées (Leguminosae - Caesalpinioideae). Flore du Gabon. Volume 15. Muséum National d’Histoire Naturelle, Paris, France. 362 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.

• de Saint-Aubin, G., 1963. La forêt du Gabon. Publication No 21 du Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 208 pp.

• Détienne, P., 2001. Du nouveau chez les andoungs. Bois et Forêts des Tropiques 267(1): 101–103.

• Sallenave, P., 1964. Propriétés physiques et mécaniques des bois tropicaux. Premier supplément. Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 79 pp.

• Sallenave, P., 1971. Propriétés physiques et mecaniques des bois tropicaux. Deuxième supplément. Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 128 pp.

• Takahashi, A., 1978. Compilation of data on the mechanical properties of foreign woods (part 3) Africa. Shimane University, Matsue, Japan. 248 pp.

• Wieringa, J.J., 1999. Monopetalanthus exit: a systematic study of Aphanocalyx, Bikinia, Icuria, Michelsonia and Tetraberlinia (Leguminosae, Caesalpinioideae). Wageningen Agricultural University Papers 99(4). Wageningen Agricultural University, Wageningen, Netherlands. 320 pp.

Other references

• CIRAD Forestry Department, 2009. Andoung. [Internet] Tropix 6.0. http://tropix.cirad.fr/ africa/andoung.pdf. August 2010.

• 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.

Sources of illustration

• Aubréville, A., 1968. Légumineuses - Caesalpinioidées (Leguminosae - Caesalpinioideae). Flore du Gabon. Volume 15. Muséum National d’Histoire Naturelle, Paris, France. 362 pp.

• de Saint-Aubin, G., 1963. La forêt du Gabon. Publication No 21 du Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 208 pp.

Author(s)

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

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

Correct citation of this article

Obeng, E.A. & Acquah, S.B., 2011. Bikinia coriacea (J.Morel ex Aubrév.) Wieringa. [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 18 December 2024.

• See the Prota4U database.