Nauclea diderrichii

Family

Rubiaceae

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Chromosome number

2n = 44

Synonyms

Sarcocephalus diderrichii De Wild. & T.Durand (1901), Sarcocephalus trillesii Pierre ex De Wild. (1901), Nauclea trillesii (Pierre ex De Wild.) Merr. (1915).

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Vernacular names

Brimstone tree, African peach (En). Acajou jaune d’Afrique, acajou jaune du Gabon, acajou jaune du Congo (Fr).

Origin and geographic distribution

Nauclea diderrichii is widespread in tropical Africa, from Guinea and Sierra Leone eastwards to Uganda and southwards to Angola. Nauclea diderrichii is frequently planted in tropical Africa, and has also been planted in trials in Brazil, Peru, Fiji and Vanuatu.

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Uses

In Ghana the wood of Nauclea diderrichii is the most popular wood for carving mortars, but it is also used for poles, mine props, furniture and drums. In Nigeria it is used for drums, poles, doors, chairs and tools. In other countries it is also used for carving sculptures and dug-out canoes. In DR Congo it was already by the end of the 19^th century in some demand for furniture. The wood, traded as ‘bilinga’, ‘opepe’ or ‘badi’, is suitable for heavy construction (including bridges, harbour works and underground construction), heavy flooring, joinery, interior trim, boat building, vehicle bodies, railway sleepers, sporting goods, toys, novelties, agricultural implements, draining boards, turnery and sliced veneer. It is also used for making canoes, as fuelwood and for charcoal production.
The pulp of the infructescence is edible, but not much eaten and mainly as a famine food. In Nigeria the leaves are fed to livestock. The root, bark and wood are used for making a yellow dye. Nauclea diderrichii is a good shade tree, used for crops as well as other timber trees.
Nauclea diderrichii is widely used in local traditional medicine. The roots are credited with diuretic properties and used for the treatment of anaemia. Bark decoctions are taken in Sierra Leone and Ghana against stomach-ache and malaria, and as a foot wash after long walks. In Côte d’Ivoire the bark is sometimes used to treat fever and jaundice. In Nigeria bark preparations are used against fever and malaria, and as antiperiodic, appetizer and diuretic. In Gabon a bark infusion is drunk against fever. In Congo bark decoctions are taken or the leaf pulp is rubbed in for the treatment of fever, stomach problems, gonorrhoea and menstruation problems, while a bark infusion is taken as a vermifuge. In DR Congo bark decoctions are drunk for the treatment of hepatitis, and drunk or used as a wash as a vermifuge. In various countries leaf infusions, leaf decoctions and the leaf pulp are drunk or used in washings, baths or embrocations to treat fever. In Guinea leaf preparations are applied on tumours. In Sierra Leone leaf decoctions are drunk against diarrhoea and a as a wash for the treatment of measles. The ripe infructescence is eaten as a cough medicine in Sierra Leone.

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Production and international trade

The wood of Nauclea diderrichii is important commercially and in high demand on the international market. According to ITTO statistics, the export from Côte d’Ivoire in 2005 was 4000 m³ of sawn wood at an average price of US$ 439/m³. Cameroon exported 4000 m³ of logs at an average price of US$ 129/m³ in 2005, and 4000 m³ at US$ 287/m³ in 2006. Congo exported 22,000 m³ of logs at an average price of US$ 124/m³ in 2004, 5000 m³ at US$ 235/m³ in 2005, and 18,000 m³ at US$ 142/m³ in 2006. Gabon exported 1000 m³ of sawn wood at an average price of US$ 320/m³ in 2004, and 1000 m³ at US$ 195/m³ in 2005. The export from Gabon was 5000 m³ of logs at an average price of US$ 118/m³ in 2008, and 4000 m³ at US$ 100/m³ in 2009.
According to ATIBT statistics, Cameroon exported 200 m³ of logs and 5500 m³ of sawn wood in 2003, 500 m³ of logs and 3700 m³ of sawn wood in 2004, and 4900 m³ of logs and 2900 m³ of sawn wood in 2006; in 1997 the export was still 31,300 m³ of logs. Congo exported 22,000 m³ of logs and 400 m³ of finished products in 2004, and 17,800 m³ of logs and 500 m³ of sawn wood in 2006. Gabon exported 49,500 m³ of logs in 2000, 19,300 m³ in 2001, 21,700 m³ in 2002, 13,500 m³ in 2003, 14,100 m³ in 2004 and 16,300 m³ in 2005. Ghana exported 7400 m³ of logs in 1998, but only 1400 m³ and 1300 m³ in 2000 and 2001, respectively, in addition to an unknown quantity of sawn wood.

Properties

The heartwood is orange or golden yellow, darkening upon exposure, and distinctly demarcated from the up to 5 cm wide, white to pale yellow, pink or grey sapwood. The grain is usually interlocked or irregular, texture moderately coarse to coarse. The wood is lustrous, and quarter-sawn surfaces have a streaked figure.
The wood is medium-weight to heavy, with a density of 670–910 kg/m³ at 12% moisture content. Quarter-sawn material dries well, with little warping or checking, but flat-sawn material may show much checking and splitting, with sometimes serious distortion. Air drying should be done slowly and carefully. Boards of 2.5 cm thick take about 9 weeks to air dry from green to 19% moisture content, and boards of 4 cm thick take about 20 days to kiln dry from green to 15% moisture content. The rates of shrinkage are moderate to high, from green to oven dry 3.7–6.3% radial and 6.2–9.2% tangential. Once dry, the wood is fairly stable in service.
The wood is strong and moderately hard to hard. At 12% moisture content, the modulus of rupture is 85–166 N/mm², modulus of elasticity 10,490–14,660 N/mm², compression parallel to grain 52–78 N/mm², shear 8.5–17 N/mm², cleavage (7–)12–24 N/mm, Janka side hardness 5790–7260 N, Janka end hardness 7140–9160 N and Chalais-Meudon side hardness 3.0–8.6.
The wood saws and works fairly well with both hand and machine tools, with normal blunting effects on saw teeth and cutting edges. In sawing, slow feeding and an angle of 17° are advised. In planing, a 10° cutting angle is recommended to avoid picking up of quarter-sawn material. The wood polishes well when a filler is used. It takes screws well but has a slight tendency to split upon nailing, and therefore pre-boring is advised. It takes waxes, paints and varnishes well. The gluing properties are good, but the steam bending properties are poor. The wood slices easily after appropriate steaming. It has a high durability with an expected service life of up to 50 years. It is resistant to attacks by fungi, termites, Anobium spp. and marine borers, but the sapwood may be susceptible to attacks by pinhole borers and powder-post beetles. The heartwood is fairly easy to treat with preservatives by pressure impregnation, the sapwood is permeable to preservatives. The presence of alkaloids in the wood may cause allergic reactions and may have serious negative effects on the health of wood workers, sometimes even resulting in death.
The energy value of the wood is 20,870 kJ/kg. Charcoal made from Nauclea diderrichii wood is of good quality. Studies in Nigeria showed that the wood produces poor quality pulpwood for paper making. The wood contains 38.5–43% cellulose, 32–35% lignin, 12–16.5% pentosan, 0.1–0.6% ash and less than 0.03% silica. The solubility is 2.8–9.1% in alcohol-benzene, 1.5–4.7% in hot water and 9.6–16.9% in a 1% NaOH solution.
A range of compounds have been isolated from the bark, such as alkaloids, secoiridoids, saponins and terpenoids. Quinovic acid glycosides (saponins) and cadambine acid (an alkaloid) isolated from the bark have shown strong in-vitro antileishmanial activity against Leishmania infantum. Hydromethanolic extracts of the bark showed significant in-vitro DNA-damage and chromosome mutations in mammalian cells, which was due to the presence of quinovic acid glycosides. Various fractions of a chloroform extract of the bark have shown in-vitro activity against Entamoeba histolytica, Trichomonas vaginalis and Leishmania donovani. Alkaloids and saponins from the bark are recorded to have antiplasmodial activity. Extracts of the stem and leaves had no antiplasmodial activity against various Plasmodium falciparum strains, and it has been suggested that the plant may have effects on the symptoms of malaria, such as fever, rather than on the parasite itself. Stem extracts have shown molluscicidal activity against the freshwater snail Bulinus globulus. Compounds isolated from the leaves include alkaloids, triterpenes, ursolic acid and β -sitosterol. Dried leaves in Nigeria contained 15.9 mg hydrogen cyanide per kg fresh weight. The roots also contain alkaloids.

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Description

Evergreen or deciduous, large to very large tree up to 50 m tall; bole branchless for up to 30 m, straight, cylindrical, up to 150(–180) cm in diameter, with low or no buttresses; bark surface scaly, shallowly longitudinally fissured, pale brown, greyish, yellowish or brownish orange, inner bark fibrous, white to pale yellow, turning pale brown to yellowish brown on exposure and becoming sticky; crown rounded, with branches in whorls, often horizontal; twigs glabrous. Leaves opposite, simple and entire; stipules interpetiolar, leaf-like, oblong-elliptical, 1–4(–8) cm long, distinctly keeled, caducous; petiole 1–3 cm long, glabrous; blade elliptical, oblong, ovate or obovate, (4–)7–30(–45) cm × (2.5–)4–16(–21) cm, cuneate to rounded at base, obtuse or slightly acuminate at apex, glabrous, pinnately veined with 4–13 pairs of lateral veins. Inflorescence a solitary, terminal, spherical head 1–4 cm in diameter; peduncle up to 4 cm long. Flowers bisexual, regular, 4–5-merous; calyx lobes prismatic or club-shaped, c. 2 mm long, thickened, hairy at apex; corolla white, greenish or yellowish, tube narrowly funnel-shaped, 6–7 mm long, lobes oblong-elliptical, 1.5–2.5 mm long, hairy inside; stamens inserted in the throat of the corolla tube, alternating with the lobes; ovary inferior, 2-celled, style exserted 4.5–6 mm from the corolla, stigma club-shaped. Fruits fused into a globose, fleshy infructescence 2–4 cm in diameter, greyish brown to orange-brown, pitted with pits 2–4 mm in diameter, rough because of the persistent calyx lobes, many-seeded. Seeds globose to ellipsoid or ovoid, c. 1 mm long, reticulate, pale brown. Seedling with epigeal germination; hypocotyl up to 2 cm long, epicotyl c. 3 mm long; cotyledons leafy, up to 5 mm long, obtuse; first leaves opposite, c. 7 mm × 4 mm, each succeeding pair of leaves bigger than previous one.

Other botanical information

Nauclea comprises about 10 species, of which 4 occur in tropical Africa and the rest in Asia. It is related to Sarcocephalus, which differs in its smaller and persistent stipules and placenta attached to the middle of the septum (to upper third of the septum in Nauclea).
Nauclea vanderguchtii (De Wild.) E.M.A.Petit is a medium-sized tree up to 30 m tall with bole up to 80 cm in diameter. It occurs along rivers and in swampy areas from southern Nigeria to DR Congo and Cabinda (Angola), but it probably also occurs in Liberia and has been recorded for Ghana as well. It can be distinguished from Nauclea diderrichii by its only slightly keeled stipules and larger infructescences (up to 10 cm in diameter), whereas young twigs are often swollen and occupied by small ants. The wood, slightly darker and softer than that of Nauclea diderrichii, is used for furniture in Nigeria and boat building in Cabinda. The infructescence is edible but is only rarely eaten. In traditional medicine in Congo, a maceration of the wood in water is taken against impotence, the bark is used in frictions applied topically for the treatment of rheumatism, and a bark decoction is drunk or the leaf pulp is rubbed in for the treatment of abdominal problems, painful menstruation and gonorrhoea.

Anatomy

Wood-anatomical description (IAWA hardwood codes):
Growth rings: 2: growth ring boundaries indistinct or absent. Vessels: 5: wood diffuse-porous; (7: vessels in diagonal and/or radial pattern); 9: vessels exclusively solitary (90% or more); 13: simple perforation plates; 22: intervessel pits alternate; 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; 47: 5–20 vessels per square millimetre. Tracheids and fibres: 62: fibres with distinctly bordered pits; 63: fibre pits common in both radial and tangential walls; 66: non-septate fibres present; 69: fibres thin- to thick-walled. Axial parenchyma: 76: axial parenchyma diffuse; 77: axial parenchyma diffuse-in-aggregates; 78: axial parenchyma scanty paratracheal; 93: eight (5–8) cells per parenchyma strand. Rays: 97: ray width 1–3 cells; 100: rays with multiseriate portion(s) as wide as uniseriate portions; 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; (112: perforated ray cells present); 116: ≥ 12 rays per mm. Mineral inclusions: (152: crystals of other shapes (mostly small)); (153: crystal sand).
(F.D. Kamala, P. Baas & H. Beeckman)

Growth and development

Natural regeneration is usually abundant in forest gaps and forest clearings. Seeds can lie dormant in the soil until they are stimulated to germinate by increased exposure to sunlight. Initial seedling growth is slow, but later growth is moderately fast. In 15-year-old unthinned stands in Ghana, the average tree height was 19.3 m, the average bole diameter 21.6 cm and the mean bole volume 0.32 m³. Trees on old logging tracks attained a height of 12 m and a diameter of 10 cm already within 4 years. In plantations in Nigeria, annual bole diameter increments of up to 1.6 cm have been obtained. In a 26-year-old taungya plantation, trees had a mean height of 16 m and a mean bole diameter of 27 cm. In 30-year-old plantations (500 trees/ha) in south-western Nigeria, the tree height was on average 23.6 m, the bole diameter 29.3 cm, the bole volume 476 m³/ha, and the total biomass 288 t/ha. In plantations in Cameroon of up to 8 years old, annual diameter increments of 3.1 cm have been recorded. In Congo planted trees of 10 years old showed a mean annual growth of 1.7 m in height and 1.8 cm in bole diameter. In Gabon 11-year-old trees planted at a density of 625 trees/ha in entirely and partially cleared land were on average 21 m and 19 m tall, with average bole diameters of 16.8 cm and 15.3 cm, respectively. In natural forest in Côte d’Ivoire, the mean annual bole diameter growth has been estimated at 6–8 mm.
Nauclea diderrichii has the ixoroid pollination mechanism, with the style head acting as a pollen receptacle where the pollen is deposited before anthesis. After the flower has opened, the style elongates and the pollen is ready for insect transfer. Later the stigma surface is revealed, being ready for pollen from other flowers. In the Central African Republic it has been observed that trees flowered for the first time when they had reached 45 cm in bole diameter. In Liberia flowering is in March–June, and ripe infructescences are found in September–December. In Sierra Leone flowering is in May–December, with heaviest fall of infructescences in October–February. In Côte d’Ivoire trees flower in January–May. In Ghana the main flowering period is May–August, while ripe infructescences can be found in September–December. The infructescences are relished by birds and form an important component of the diet of mammals such as elephants, duikers and monkeys, which probably help to disperse the seeds.

Ecology

Nauclea diderrichii occurs from sea-level up to 1650 m altitude in areas with an average annual rainfall of (1200–)1600–3500(–4500) mm, and a dry season of 0–6 months. It is a light-demanding pioneer species, and grows in a wide range of habitats, occurring particularly in humid evergreen forest and moist semi-deciduous forest. It is also found in swampy areas. Nauclea diderrichii prefers light to medium textured, well-drained, neutral to slightly acid soils, and does not grow well on excessively wet soils or on lateritic soils. In Sierra Leone, it is typically associated with other light-demanding species such as Bridelia grandis Pierre ex Hutch., Terminalia ivorensis A.Chev. and Zanthoxylum gilletii (De Wild.) P.G.Waterman.

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Propagation and planting

Nauclea diderrichii regenerates profusely in large forest gaps and along roads in the vicinity of mother trees. It is easily propagated from seeds, cuttings and wildlings. Reports on the 1000-seed weight vary widely, from 1 g to 18 g. Seeds are extracted from dried infructescences by pounding. Seed treatment is not necessary, but germination is faster when the seeds have been soaked in water or buried in damp soil before sowing. Seed can be stored in airtight containers, with the viability retained for over a year. It is usually sown broadcast and covered with a thin layer of sand or sown in seed beds. Germination takes place in 2–4 weeks, with a germination rate of 50–75%. Excessive watering of seedlings should be avoided to prevent losses through damping-off at the nursery. It is recommended to prick out the seedlings after 1.5–2 months, when they are 10–15 cm long and have 4–6 leaves, and plant them into seedbeds at a spacing of 25 cm, but care should be taken to avoid damaging or wilting of the soft stems. Seedlings can be planted out when 1–1.5 years old. Because of the soft stems, they are best stumped before planting out. Planting out is done at a spacing of 2.5–4.5 m × 2.5–3 m.

Management

In Ghana the density of larger Nauclea diderrichii trees in the forest is generally quite low. In Cameroon as well the density is low, with an average number of trees with a bole diameter of more than 60 cm up to 0.1 per ha and a mean bole volume up to 0.7 m³/ha. In Gabon the wood volume has been estimated at 0.5 m³/ha.
In cultivation, Nauclea diderrichii can be managed by side pruning, thinning and coppicing. Young saplings are often multi-stemmed, and it is advisable to prune the secondary stems in the early years of a plantation. A rotation cycle of 30–40 years is needed to obtain trees with a diameter of 50 cm. In Côte d’Ivoire recommended silvicultural practices include planting at a density of 1100 seedlings per ha, first thinning after 5 years to 400–500 stems per ha, second thinning after 9–10 years to 200–250 stems per ha and third thinning after 15 years to 125–160 stems per ha. Nauclea diderrichii is commonly grown in taungya plantations and is recommended as a nurse crop for valuable Meliaceae trees such as Lovoa trichilioides Harms and Khaya spp. In Côte d’Ivoire it was successfully mixed with Heritiera utilis (Sprague) Sprague.

Diseases and pests

In nurseries and young plantations, especially in open conditions, Nauclea diderrichii may be attacked by larvae of the shoot-boring moth Orygmophora mediofoveata, resulting in stunted growth, death of the principal shoot and formation of multiple shoots. Infestation levels of 30–80% have been recorded in Nigeria in the 1960s, and more recently in nurseries in Ghana 60–80% of the potted seedlings were found to be destroyed. Especially in Ghana this pest is a serious factor limiting the possibilities of pure Nauclea diderrichii plantations. For its control, the use of insecticides has been recommended and in Ghana research has been started on silvicultural control practices and genetic resistance. Monkeys can cause top damage to young saplings.

Harvesting

The minimum bole diameter for harvesting Nauclea diderrichii is 110 cm in Ghana, 80 cm in Liberia, Cameroon and Gabon, and 60 cm in Côte d’Ivoire, Central African Republic and DR Congo.

Handling after harvest

Freshly harvested boles usually do not float in water and thus cannot be transported by river. Brittle heart may be present in large logs.

Genetic resources and breeding

Nauclea diderrichii has a large distribution area, but is in many regions uncommon and heavily exploited. Although its regeneration is usually good in large forest gaps, it is often outcompeted by other pioneer species. Therefore, it is included as vulnerable in the IUCN Red list of threatened species, with the observation that the status of the species should be kept under review. In Liberia an export ban has been implemented on this species, and in Ghana a special felling permit is needed since 1998.

Prospects

Nauclea diderrichii is a popular commercial timber species, yielding very durable wood with good mechanical properties. Its density in the natural forest is low, however, and to ensure sustainable exploitation of the species, more research is needed on appropriate management systems in natural forest and on the establishment of commercial plantations. It has good prospects for wider-scale planting for timber production because it combines excellent wood properties with fair growth rates. More research on the chemical constituents for possible drug development in the pharmaceutical industry also seems warranted.

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.
• Bridson, D. & Verdcourt, B., 1988. Rubiaceae (part 2). In: Polhill, R.M. (Editor). Flora of Tropical East Africa. A.A. Balkema, Rotterdam, Netherlands. pp. 415–747.
• Burkill, H.M., 1997. The useful plants of West Tropical Africa. 2nd Edition. Volume 4, Families M–R. Royal Botanic Gardens, Kew, Richmond, United Kingdom. 969 pp.
• CAB International, 2005. Forestry Compendium. Nauclea diderrichii (Bilinga). [Internet] http://www.cabi.org/ fc/. Accessed May 2010.
• CIRAD Forestry Department, 2009. Bilinga. [Internet] Tropix 6.0. http://tropix.cirad.fr/ africa/ bilinga.pdf. Accessed May 2010.
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• Onyekwelu, J.C., 2007. Growth, biomass yield and biomass functions for plantation-grown Nauclea diderrichii (De Wild.) in the humid tropical rainforest zone of south-western Nigeria. Bioresource Technology 98(14): 2679–2687.
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Other references

• Adu-Anning, C. & Anglaaere, L.C.N., 1997. Biomass and nutrient accumulation and distribution in a 15-year old unthinned stands of Nauclea diderrichii and Funtumia elastica in the moist semi-deciduous forest of Ghana. Ghana Journal of Forestry 5: 57–66.
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• di Giorgio, C., Lamidi, M., Delmas, F., Balansard, G. & Ollivier, E., 2006. Antileishmanial activity of quinovic acid glycosides and cadambine acid isolated from Nauclea diderrichii. Planta Medica 72(15): 1396–1402.
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Afriref references

Sources of illustration

• Bridson, D. & Verdcourt, B., 1988. Rubiaceae (part 2). In: Polhill, R.M. (Editor). Flora of Tropical East Africa. A.A. Balkema, Rotterdam, Netherlands. pp. 415–747.
• 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.

Author(s)

•	N.Y. Opuni-Frimpong Forestry Research Institute of Ghana (FORIG), University P.O. Box 63, KNUST, Kumasi, Ghana
•	E. Opuni-Frimpong Forestry Research Institute of Ghana (FORIG), University P.O. Box 63, KNUST, 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

Opuni-Frimpong, N.Y. & Opuni-Frimpong, E., 2012. Nauclea diderrichii (De Wild. & T.Durand) Merr. [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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