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Piptadeniastrum africanum (Hook.f.) Brenan

Protologue
Kew Bull. 1955(2): 179 (1955).
Family
Mimosaceae (Leguminosae - Mimosoideae)
Chromosome number
2n = 26
Synonyms
Piptadenia africana Hook.f. (1849).
Vernacular names
Dabema, dahoma, African greenheart (En). Dabéma (Fr). Musence (Po).
Origin and geographic distribution
Piptadeniastrum africanum occurs from Senegal east to southern Sudan and Uganda, and south to DR Congo and northern Angola.
Uses
The wood (trade names: dabema, dahoma) is used for construction, including marine construction and bridges, flooring, railway sleepers, mine props, ship building, vehicle bodies, interior trim, joinery, furniture, including garden furniture, cabinet work, sporting goods, turnery, hardboard, particle board and pulpwood. It is used traditionally to make dug-out canoes. In Europe the wood is considered an excellent replacement for oak (Quercus spp.), and is sometimes called ‘African oak’. It is also used as fuelwood and for charcoal production.
Piptadeniastrum africanum is commonly used in traditional medicine, mostly the bark, sometimes also roots and leaves. Bark decoctions are used internally to treat cough, bronchitis, headache, mental disorders, haemorrhoids, genito-urinary infections, stomach-ache, dysmenorrhoea and male impotence, and as an antidote; externally, they are applied to treat fever, toothache, pneumonia, oedema, skin complaints and rheumatism, to expel worms, to dispel fleas, and as a purgative and abortifacient. A decoction of the bark also enters in a complex treatment of leprosy. The bark is used in arrow poison, and as ordeal poison and fish poison; mixed with rice it is used to poison mice. It is also used as a soap substitute. Pygmy people in Cameroon and DR Congo use both root bark and stem bark as an ingredient of arrow poison. Root extracts or macerations are applied against mental disorders, and as an abortifacient and aphrodisiac. Pounded leaves and leaf decoctions are applied as an enema to treat gonorrhoea and abdominal complaints. Leaves are used to poison mice.
The tree is planted or left during forest clearing as a shade tree in coffee, cocoa and banana plantations. The bark fibre has been used to weave mats. Edible caterpillars feed on the leaves, and the flowers are a source of nectar for honey bees. In various countries Piptadeniastrum africanum is considered a magic tree.
Production and international trade
According to ITTO, Ghana exported 4000 m³/year of sawn dabema wood in 2003 and 2004, at an average price of US$ 310/m³. Côte d’Ivoire exported 10,000 m³ of sawnwood in 2004, at an average price of US$ 397/m³, and 4000 m³ in 2005, at US$ 439/m³. Cameroon exported 7000 m³ of logs in 2005, at an average price of US$ 555/m³, and in 2006 the volume was 14,000 m³, at US$ 358/m³. According to ATIBT (‘Association technique internationale des bois tropicaux’), Cameroon exported 400 m³ of sawnwood in 2003, 800 m³ in 2004, and 2000 m³ in 2006, whereas log exports were 21,000 m³ in 2006. Gabon exported 950 m³/year of logs in 2003 and 2004, and 15,000 m³ in 2005.
Properties
The heartwood is pale brown to golden brown, occasionally dark brown, with an attractive stripe pattern on quarter-sawn surfaces, distinctly demarcated from the 5–15 cm thick, pale pink to greyish red sapwood. The grain is interlocked, texture coarse. The wood has an unpleasant ammoniac smell when freshly cut.
The wood is moderately heavy. At 12% moisture content, the density is (480–)590–800(–900) kg/m³. The rates of shrinkage during drying are moderate to high, from green to oven dry 2.5–5.2% radial and 7.0–10.5(–13.4)% tangential. The wood air dries rather slowly, with high risk of distortion and checking. In southern Côte d’Ivoire boards 29 mm thick in horizontal roofed piles take 38 weeks to dry, and 50 mm boards 61 weeks. Air drying prior to kiln drying is recommended. After drying, the wood is moderately stable in service.
At 12% moisture content, the modulus of rupture is 80–178 N/mm², modulus of elasticity 9300–16,500 N/mm², compression parallel to grain 46–74 N/mm², shear 7–18 N/mm², cleavage 14–32 N/mm, Janka side hardness 6400–6860 N and Janka end hardness 8100 N.
The wood is fairly easy to saw and work, but with some blunting effect on cutting edges, so the use of stellite-tipped sawteeth and tungsten-carbide-tipped cutting tools is recommended. A cutting angle of 10–15° is recommended in planing and moulding operations to avoid picking-up of grain. The wood finishes well, but the use of a filler is needed. It holds screws and nails well, but there is a slight tendency for splitting. The gluing properties are satisfactory. The steam bending properties are moderate. The wood is not particularly suitable for veneer or plywood production; it should be well steamed to make peeling possible. The sawdust may irritate skin, throat and eyes.
The heartwood is moderately durable. It showed moderate resistance to fungal, dry-wood borer and termite attacks. In tests in Ghana, the wood showed no damage after being subjected to Coptotermes formosanus termites in exposure chambers, all termites being dead within one week. It is recorded as durable in fresh water. The heartwood does not absorb preservatives, but the sapwood is only moderately resistant. However, it is also reported that for use as railway sleepers impregnation is needed. The degree of resistance to fungal attacks depends on the concentration of dihydroflavonols, which is higher in the outer part of the heartwood than in the inner part, which is thus less durable.
Kraft pulping experiments showed that the wood has good prospects for paper production. In Ghana the charcoal made from the wood has been found to be suitable for preparation of activated, decolorizing carbon used in sugar refining.
The roots and stem bark contain saponins, tannins, flavonoids and leucoanthocyanes. The stem bark is very toxic; this has been confirmed by tests with rats. It showed moderate activity against several pathogenic bacteria.
Adulterations and substitutes
The timber of Cylicodiscus gabunensis Harms is similar although slightly heavier, and is also traded as African greenheart.
Description
Deciduous or evergreen large tree up to 50 m tall; bole straight and cylindrical, but sometimes sinuous, branchless for up to 20(–30) m, up to 180(–300) cm in diameter at base, with large, thin buttresses up to 5(–8) m high, often extending into branched and sinuous surface plank roots; bark surface smooth, sometimes with ring marks and numerous small lenticels, in old trees sometimes slightly fissured, yellowish brown to greyish brown or reddish brown, inner bark whitish to pale yellow or brown, brittle; crown spreading, flat; young twigs densely brown short-hairy. Leaves alternate, bipinnately compound with 10–19 pairs of usually alternate pinnae; stipules linear, up to 9 mm long, early caducous; petiole 0.5–3 cm long; leaflets opposite, 25–60 pairs per pinna, sessile, linear, 1.5–8.5 mm × c. 1 mm, asymmetrical at base, obtuse at apex, hairy at margin. Inflorescence an axillary or terminal spike-like false raceme up to 11 cm long, often many together at ends of twigs, hairy, densely flowered. Flowers bisexual, regular, 5-merous; pedicel c. 0.5 mm long; calyx with c. 0.5 mm long tube, toothed; petals free, oblong to lanceolate, 2.5–3 mm long, whitish or yellowish; stamens 10, fused at base, c. 4 mm long, anthers with gland at apex; ovary superior, ellipsoid, c. 2 mm long, with c. 1 mm long stipe, glabrous, style slender. Fruit a flattened linear pod 12.5–36 cm × 1.5–3 cm, shortly stiped at base, dark brown, transversely veined, dehiscent at one side, up to 9-seeded. Seeds oblong, flat, 3–9.5 cm long including the papery wing surrounding the seed, glossy brown, attached at the middle. Seedling with epigeal germination; hypocotyl 1–3 cm long, epicotyl c. 3 cm long; cotyledons shell-shaped, c. 1 cm × 2.5 cm, slightly fleshy; first leaves pinnately compound with many leaflets.
Other botanical information
Piptadeniastrum comprises a single species and seems to have a rather isolated position within its family. It may be confused with Newtonia, which differs in the presence of glands on the leaves, its hairy ovary and its seeds being attached at the apex.
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; 26: intervessel pits medium (7–10 μm); 27: intervessel pits large ( 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); 43: mean tangential diameter of vessel lumina 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; (65: septate fibres present); 66: non-septate fibres present; 69: fibres thin- to thick-walled. Axial parenchyma: (76: axial parenchyma diffuse); 79: axial parenchyma vasicentric; 80: axial parenchyma aliform; 81: axial parenchyma lozenge-aliform; 83: axial parenchyma confluent; 91: two cells per parenchyma strand; 92: four (3–4) cells per parenchyma strand; (93: eight (5–8) cells per parenchyma strand). Rays: 98: larger rays commonly 4- to 10-seriate; 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.
(E. Uetimane, H. Beeckman & P.E. Gasson)
Growth and development
Seedlings are often common in the forest, even in dark shade. However, they grow very poorly in shade, where they may be only 20–35 cm tall when 3 years old, whereas they may reach up to 150 cm tall after 4 years in less shaded conditions in the forest. Saplings and young trees demand light, and are usually found in small gaps in the forest. In Sierra Leone mean annual bole diameter increments of 1.2 cm have been recorded for the first 20 years after planting. In Côte d’Ivoire the mean annual diameter increment was 4.9 mm. In Ghana mean annual diameter increments were highest in the diameter classes of 30–49 cm and 50–69 cm, with 9.0 mm and 11.1 mm respectively. In Nigeria a tree reached 90 cm bole diameter in 71 years.
Young trees have a rounded crown, which develops into 2 distinct layers, of which the lower one disappears later and the upper one develops horizontally and ultimately becomes fragmented. Adult trees have huge, flat crowns that spread in the upper canopy of the forest. The trees are often briefly deciduous, but frequently do not shed all leaves at the same time. The leaflets fold up at sunset. In Sierra Leone, Liberia and Côte d’Ivoire trees usually flower in May–August and fruits mature in December–March; in Nigeria flowering has been observed in June–September and fruiting in October–March. In Ghana fruits are ripe towards the end of the dry season. In Uganda flowering occurs mainly in July and August. The winged seeds are mainly dispersed by wind, but distribution by water and birds is also possible. Piptadeniastrum africanum nodulates with rhizobia.
Ecology
Piptadeniastrum africanum occurs in lowland evergreen and semi-deciduous forest, up to 1200 m altitude. In Ghana it shows a preference for evergreen forest. In Gabon it occurs scattered in primary forest, but may be locally more abundant in old secondary forest. Some preference for hillsides and moist but well-drained level ground has been recorded for Sierra Leone, but Piptadeniastrum africanum is also commonly found in riverine forest. In Uganda it is a common and characteristic species of the forest in the Lake Victoria belt.
Propagation and planting
Seeds for planting are collected from the forest floor. The 1000-seed weight is about 180 g. Seeds lose their viability quickly and cannot be stored for more than one month. They do not show dormancy, and germinate in 1–3 weeks. In a germination test, 96% of the seeds germinated within 8 days. They should be sown in shaded nursery beds. The growth of seedlings is slow and they may stay in the nursery for more than one year before planting. Wildlings are sometimes collected for planting.
Management
In general Piptadeniastrum africanum occurs rather scattered in the forest. In Gabon the average bole volume is 0.6 m³/ha, but in southern Cameroon it is 1.6–4.8 m³/ha for bole diameters over 60 cm. In some regions Piptadeniastrum africanum occurs in high densities, e.g. in some forests in Sierra Leone, where it may account for 10% of all trees of over 60 cm bole diameter. In Liberia an average density of up to 1 bole over 60 cm diameter per ha has been recorded. In Uganda Piptadeniastrum africanum has been planted successfully in experimental plantations.
Harvesting
The minimum felling diameter is 60 cm in Côte d’Ivoire, Cameroon and DR Congo, 80 cm in Liberia and the Central African Republic, and 90 cm in Ghana. The high buttresses at the base of the bole necessitate the construction of a platform before felling can take place. The boles have a tendency to split during felling operations.
Yield
Trees with a bole diameter of 60, 90 and 120 cm yield about 3.1, 7.2 and 13.1 m³ of timber, respectively.
Handling after harvest
Freshly harvested logs sink in water and thus cannot be transported by river.
Genetic resources
Piptadeniastrum africanum is widespread in different forest types in West and Central Africa and is common in many regions. Therefore, it does not seem to be threatened at present. However, it seems to be gaining in importance as a commercial timber tree, and the bark is commonly partially removed for applications in traditional medicine. This may make Piptadeniastrum africanum liable to genetic erosion in the near future.
Prospects
There is much demand on the international timber market for Piptadeniastrum africanum, although the applications of the wood are somewhat limited due to the high shrinkage rates. This demand offers possibilities for increased commercialization of the species, but research is needed on growth rates under different ecological conditions and the development of suitable management methods for forest in which it is a common constituent to guarantee sustainable production in the future.
Although Piptadeniastrum africanum has numerous applications in traditional medicine, very little research has been done on its phytochemistry and pharmacological properties. Research is warranted to assess its possibilities for drug development, but also in the light of the known toxic effects of the bark, which is the most commonly used part of the tree in local medicine.
Major references
• ATIBT (Association Technique Internationale des Bois Tropicaux), 1986. Tropical timber atlas: Part 1 – Africa. ATIBT, Paris, France. 208 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.
• 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.
• CTFT (Centre Technique Forestier Tropical), 1974. Dabema. Bois et Forêts des Tropiques 156: 27–38.
• Katende, A.B., Birnie, A. & Tengnäs, B., 1995. Useful trees and shrubs for Uganda: identification, propagation and management for agricultural and pastoral communities. Technical Handbook 10. Regional Soil Conservation Unit, Nairobi, Kenya. 710 pp.
• Neuwinger, H.D., 1996. African ethnobotany: poisons and drugs. Chapman & Hall, London, United Kingdom. 941 pp.
• Phongphaew, P., 2003. The commercial woods of Africa. Linden Publishing, Fresno, California, United States. 206 pp.
• Savill, P.S. & Fox, J.E.D., 1967. Trees of Sierra Leone. Forest Department, Freetown, Sierra Leone. 316 pp.
• Takahashi, A., 1978. Compilation of data on the mechanical properties of foreign woods (part 3) Africa. Shimane University, Matsue, Japan, 248 pp.
• 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.
Other references
• Adjanohoun, E.J., Ahyi, A.M.R., Aké Assi, L., Baniakina, J., Chibon, P., Cusset, G., Doulou, V., Enzanza, A., Eymé, J., Goudoté, E., Keita, A., Mbemba, C., Mollet, J., Moutsamboté, J.-M., Mpati, J. & Sita, P. (Editors), 1988. Médecine traditionnelle et pharmacopée - Contribution aux études ethnobotaniques et floristiques en République Populaire du Congo. Agence de Coopération Culturelle et Technique, Paris, France. 606 pp.
• CIRAD Forestry Department, 2003. Dabema. [Internet] Tropix 5.0. http://tropix.cirad.fr/ afr/dabema.pdf. Accessed October 2007.
• 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.
• Déon, G. & Schwartz, R., 1988. Résistance naturelle des bois tropicaux aux attaques biologiques. Bulletin de la Société Botanique de France 135, Actualités Botanique 1988-3: 37–48.
• de Saint-Aubin, G., 1963. La forêt du Gabon. Publication No 21 du Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 208 pp.
• Durrieu de Madron, L., Nasi, R. & Détienne, P., 2000. Accroissements diamétriques de quelques essences en forêt dense africaine. Bois et Forêts des Tropiques 263(1): 63–74.
• Farmer, R.H., 1972. Handbook of hardwoods. 2nd Edition. Her Majesty’s Stationery Office, London, United Kingdom. 243 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.
• 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.
• InsideWood, undated. [Internet] http://insidewood.lib.ncsu.edu/search/. Accessed May 2007.
• 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.
• Latham, P., 2004. Useful plants of Bas-Congo province, Democratic Republic of the Congo. DFID, London, United Kingdom. 320 pp.
• Lewis, G., Schrire, B., MacKinder, B. & Lock, M., 2005. Legumes of the world. Royal Botanic Gardens, Kew, Richmond, United Kingdom. 577 pp.
• Neuwinger, H.D., 2000. African traditional medicine: a dictionary of plant use and applications. Medpharm Scientific, Stuttgart, Germany. 589 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.
• Noumi, E. & Tchakonang, N.Y.C., 2001. Plants used as abortifacients in Sangmelima region of southern Cameroon. Journal of Ethnopharmacology 76: 263–268.
• Onanga, M., Ekouya, A., Ouabonzi, A. & Itoua, G.B., 1999. Ethnobotanical, pharmacological and chemical studies of plants used in the treatment of ‘Mwandza’ dermatites. Fitoterapia 70: 579–585.
• Siepel, A., Poorter, L. & Hawthorne, W.D., 2004. Ecological profiles of large timber species. In: Poorter, L., Bongers, F., Kouamé, F.N. & Hawthorne, W.D. (Editors). Biodiversity of West African forests. An ecological atlas of woody plant species. CABI Publishing, CAB International, Wallingford, United Kingdom. pp. 391–445.
• Sprent, J.I., 2001. Nodulation in legumes. Royal Botanic Gardens, Kew, United Kingdom. 146 pp.
• Villiers, J.-F., 1989. Leguminosae - Mimosoideae. Flore du Gabon. Volume 31. Muséum National d’Histoire Naturelle, Paris, France. 185 pp.
• Vivien, J. & Faure, J.J., 1985. Arbres des forêts denses d’Afrique Centrale. Agence de Coopération Culturelle et Technique, Paris, France. 565 pp.
Sources of illustration
• Brenan, J.P.M., 1959. Leguminosae subfamily Mimosoideae. In: Hubbard, C.E. & Milne-Redhead, E. (Editors). Flora of Tropical East Africa. Crown Agents for Oversea Governments and Administrations, London, United Kingdom. 173 pp.
• 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.
• Wilks, C. & Issembé, Y., 2000. Les arbres de la Guinée Equatoriale: Guide pratique d’identification: région continentale. Projet CUREF, Bata, Guinée Equatoriale. 546 pp.
Author(s)
R.B. Jiofack Tafokou
Ecologic Museum of Cameroon, P.O. Box 8038, Yaoundé, Cameroon


Editors
D. Louppe
CIRAD, Département Environnements et Sociétés, Cirad es-dir, Campus international de Baillarguet, TA C-DIR / B (Bât. C, Bur. 113), 34398 Montpellier Cedex 5, France
A.A. Oteng-Amoako
Forestry Research Institute of Ghana (FORIG), University P.O. Box 63, KNUST, Kumasi, Ghana
M. Brink
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
General editors
R.H.M.J. Lemmens
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
L.P.A. Oyen
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
J.R. Cobbinah
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:
Jiofack Tafokou, R.B., 2008. Piptadeniastrum africanum (Hook.f.) Brenan. In: Louppe, D., Oteng-Amoako, A.A. & Brink, M. (Editors). Prota 7(1): Timbers/Bois d’œuvre 1. [CD-Rom]. PROTA, Wageningen, Netherlands.

















































Distribution Map wild


1, base of bole; 2, flowering twig; 3, fruit; 4, seed.
Redrawn and adapted by Achmad Satiri Nurhaman



tree habit


bark


bark and slash


flowering branches


fruits and seeds


germinating seeds


seedling


planks


cross-section of log


wood (tangential surface)


wood (radial surface)


wood in transverse section


wood in tangential section


wood in radial section