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Autranella congolensis (De Wild.) A.Chev.

Protologue
Veg. Ut. Afr. Trop. Franç. 9: 271 (1917).
Family
Sapotaceae
Chromosome number
2n = 26
Synonyms
Mimusops letestui Lecomte (1920).
Origin and geographic distribution
Autranella congolensis occurs from south-eastern Nigeria east to the Central African Republic, and south to Gabon and DR Congo.
Uses
The wood (trade name: mukulungu) is used for heavy construction, heavy-duty flooring, bridges, sluice gates and other waterworks, railway sleepers, stairs, poles, vats, vehicle bodies and quarter-sliced veneer. It is locally used to make canoes and paddles. It is suitable for joinery, marquetry, turnery, interior trim, furniture and cabinet work, sporting goods, toys and novelties, musical instruments, draining boards, agricultural implements, ship and boat building and mine props.
The fruits are reported to be edible. An edible oil is extracted from the seeds; it is used for cooking in Gabon. Dry ground bark is applied to cuts and sores. A bark decoction is taken to treat gonorrhoea, syphilis, dyspepsia, colic and colds, and applied externally to treat fever, pain, skin diseases and wounds. The broken seed coats are strung together to make rattles.
Production and international trade
Autranella congolensis timber is exported in small amounts from Central Africa. According to ATIBT figures, in 2001 the log export from Cameroon was 235 m³ and from Gabon 105 m³. In 2003 about 930 m³ of sawnwood was exported from Cameroon.
Properties
The heartwood is reddish brown with dark brown streaks, and usually distinctly demarcated from the greyish or brownish sapwood, which is 1–3 cm wide. The grain is straight or sometimes interlocked, texture fine and even. The wood is heavy, with a density of 910–990 kg/m³ at 12% moisture content. It dries slowly, with severe risk of deformation; it needs to be dried with care and quartersawing is recommended. The shrinkage rates are moderate to high, from green to oven dry 3.9–9.0% radial and 4.1–9.1% tangential. Once dry, the wood is often unstable in service.
At 12% moisture content, the modulus of rupture is 120–199 N/mm², modulus of elasticity 11,800–21,900 N/mm², compression parallel to grain 66–105 N/mm², shear 6.4–13.2 N/mm², cleavage 18.1–22.5 N/mm, Janka side hardness 10,230 N and Janka end hardness 12,370 N.
The wood saws easily but slowly, with serious blunting effect on tools due to the high density and the presence of silica. Stellite-tipped sawteeth and tungsten- carbide-tipped cutting tools are recommended. The wood planes fairly easily with a smooth finish. It holds nails and screws well, but pre-boring is needed. The gluing properties are poor to satisfactory. It can be used for sliced veneer, but rotary peeling is difficult. It is resistant to acids, making it suitable for chemical containers and laboratory tables.
The wood is durable and resistant to fungi and dry-wood borers, but sometimes there is slight termite attack. It is considered resistant to marine borers, but in tests in Italy it was not resistant. It is resistant to impregnation with preservatives. The wood dust may cause serious irritation to nose, throat and eyes. The presence of saponins has been reported for the wood, which contributes to the resistance to fungi.
Adulterations and substitutes
The wood of Autranella congolensis is similar to that of Baillonella toxisperma Pierre (moabi), which is used for similar purposes. It also resembles Tieghemella wood, but this has a lower density.
Description
Medium-sized to large tree up to 40(–50) m tall; bole straight and cylindrical, branchless for up to 30 m, up to 150(–200) cm in diameter, often slightly buttressed at base; bark surface brown, fissured, inner bark red to brown, fibrous, exuding latex; crown umbrella-shaped, flattened; branches with numerous leaf scars. Leaves arranged spirally, clustered at ends of branches, simple and entire; stipules triangular, early caduceus; petiole slender, 4–5 cm long, channelled above; blade elliptical-oblong to slightly obovate, 10–15 cm × 4–5 cm, rounded to cuneate at base, rounded to shortly acuminate at apex, leathery, glabrous, pinnately veined with c. 15 pairs of indistinct lateral veins. Inflorescence an axillary fascicle at the ends of branches. Flowers bisexual, regular; pedicel c. 2 cm long; sepals free, in 2 whorls of 4, oblong, c. 1 cm long, obtuse at apex, hairy; corolla with c. 7.5 mm long tube and 8 lobes c. 2.5 mm long, divided to base into 3 segments with median segment erect and clasping stamen, and lateral segments much larger and spreading or reflexed, segments shortly hairy inside; stamens inserted at top of corolla tube opposite corolla lobes, almost sessile, alternating with short staminodes; ovary superior, ellipsoid, large, hairy, 8-celled, gradually narrowed into the short style. Fruit a fleshy, ovoid to ellipsoid 1(–2)-seeded berry 5–10 cm long, warty, yellowish green. Seed obovoid, slightly flattened, c. 4.5 cm long, glossy brown, with fairly large rectangular scar. Seedling with epigeal germination; hypocotyl 14–22 cm long, epicotyl 1–4.5 cm long; cotyledons elliptical, 6–10 cm long, leafy but leathery; leaves alternate from the beginning.
Other botanical information
Autranella comprises a single species. It seems to be related to Mimusops and Tieghemella, the former of which differs in lacking stipules and having a shorter corolla tube and smaller fruits, the latter in lacking stipules and having stamens and staminodes inserted near the base of the corolla tube and larger seed scar. Baillonella toxisperma resembles Autranella congolensis, but differs in its shorter corolla tube, distinct stamen filaments and larger seed scar.
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; (8: vessels in dendritic pattern); (10: vessels in radial multiples of 4 or more common); (11: vessel clusters common); 13: simple perforation plates; 22: intervessel pits alternate; 26: intervessel pits medium (7–10 μm); 30: vessel-ray pits with distinct borders; similar to intervessel pits in size and shape throughout the ray cell; 31: vessel-ray pits with much reduced borders to apparently simple: pits rounded or angular; 32: vessel-ray pits with much reduced borders to apparently simple: pits horizontal (scalariform, gash-like) to vertical (palisade); 33: vessel-ray pits of two distinct sizes or types in the same ray cell; (34: vessel-ray pits unilaterally compound and coarse (over 10 μm)); 42: mean tangential diameter of vessel lumina 100–200 μm; 47: 5–20 vessels per square millimetre; 56: tyloses common. Tracheids and fibres: 61: fibres with simple to minutely bordered pits; 66: non-septate fibres present; 70: fibres very thick-walled. Axial parenchyma: (76: axial parenchyma diffuse); 86: axial parenchyma in narrow bands or lines up to three cells wide; 87: axial parenchyma reticulate; 93: eight (5–8) cells per parenchyma strand; 94: over eight cells per parenchyma strand. Rays: 97: ray width 1–3 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); 115: 4–12 rays per mm. Mineral inclusions: 136: prismatic crystals present; 142: prismatic crystals in chambered axial parenchyma cells; 159: silica bodies present; 160: silica bodies in ray cells; (161: silica bodies in axial parenchyma cells).
(H. Beeckman & P. Détienne)
Growth and development
The fruits take 10–14 months to ripen. It has been reported that in the dry season many young fruits fall, long before they are ripe. Elephants eat the fruits and are probably the main seed dispersers. It is unknown whether seeds that have passed through elephants’ guts germinate more easily, but seeds that have not been eaten by elephants do germinate although the germination rate is low. Seedlings grow slowly. After germination, growth of aerial parts stops for about 2 months, after which seedlings grow at a rate of 1 cm per month, reaching an average height of 25 cm after 18 months and 36 cm after 29 months. Autranella congolensis forms arbuscular mycorrhizae with Glomeromycete spp.
Ecology
Autranella congolensis occurs in primary evergreen rainforest, usually scattered, rarely abundant.
Propagation and planting
The seeds with their thick and hard seed coat show a dormancy of 2.5–12 months before germinating. The germination rate may be up to 40%, but is often lower; the germination rate of depulped seeds is lowest, up to 9%. In the forest, seedlings of Autranella congolensis are often rare. Under experimental nursery conditions, the survival rate of seedlings was 100% after 18 months. The seedlings are shade tolerant, but are classified as non-pioneer light demanders, preferring small gaps in the forest canopy.
Management
In general Autranella congolensis occurs in low densities in the forest, but locally in DR Congo 3–4 large trees per ha have been recorded.
Diseases and pests
The seeds with their thick and hard seed coat are not as easily attacked by insects as those of moabi (Baillonella toxisperma). The seedlings with their leafy cotyledons are also less commonly eaten by bush pigs, antelopes and porcupines than those of moabi with fleshy cotyledons.
Harvesting
Logs may split in the centre at felling and they also may show other defects in the central part.
Yield
A large Autranella congolensis tree may yield up to 20 m³ of usable wood.
Handling after harvest
Logs sink in water and cannot be transported by river. They have a good durability and can be left in the forest for considerable time without serious degrade.
Genetic resources
Autranella congolensis is classified as critically endangered in the 2006 IUCN Red list of threatened species, with heavy exploitation for its timber being the main threat.
Prospects
It will be difficult to manage natural forest in such a way that sustainable and economically sufficient production of Autranella congolensis timber is possible. Larger trees generally occur scattered in low densities. Natural regeneration is poor, and the low germination rate and dormancy of the seeds hamper large-scale production of seedlings for transplanting. Moreover, growth is slow and very long cutting cycles are probably required for sustainable harvesting. This makes Autranella congolensis a tree with few prospects for commercial timber production, and attention should concentrate on its protection.
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.
• CTFT (Centre Technique Forestier Tropical), 1954. Mukulungu 1. Fiche botanique et forestière. Bois et Forêts des Tropiques 36: 25–28.
• Chudnoff, M., 1980. Tropical timbers of the world. USDA Forest Service, Agricultural Handbook No 607, Washington D.C., United States. 826 pp.
• CIRAD Forestry Department, 2003. Mukulungu. [Internet] Tropix 5.0. http://tropix.cirad.fr/ afr/mukulungu.pdf. Accessed November 2006.
• Debroux, L., Delvingi, W., Mbolo, M. & Amougou, A., 1998. Régénération du moabi et du mukulungu au Cameroun, perspectives pour l’aménagement. Bois et Forêts des Tropiques 225(1): 1–17.
• 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.
• Richter, H.G. & Dallwitz, M.J., 2000. Commercial timbers: descriptions, illustrations, identification, and information retrieval. [Internet]. Version 18th October 2002. http://delta-intkey.com/wood/index.htm. Accessed November 2006.
• Takahashi, A., 1978. Compilation of data on the mechanical properties of foreign woods (part 3) Africa. Shimane University, Matsue, Japan, 248 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.
Other references
• African Regional Workshop (Conservation & Sustainable Management of Trees, Zimbabwe), 1998. Autranella congolensis. In: IUCN. 2006 Red list of threatened species. [Internet] http://www.iucnredlist.org. Accessed March 2007.
• Aubréville, A., 1961. Sapotacées. Flore du Gabon. Volume 1. Muséum National d’Histoire Naturelle, Paris, France. 162 pp.
• Aubréville, A., 1964. Sapotacées. Flore du Cameroun. Volume 2. Muséum National d’Histoire Naturelle, Paris, France. 143 pp.
• Burkill, H.M., 2000. The useful plants of West Tropical Africa. 2nd Edition. Volume 5, Families S–Z, Addenda. Royal Botanic Gardens, Kew, Richmond, United Kingdom. 686 pp.
• Déon, G., Chadenson, M. & Hauteville, M., 1980. Influence des extraits naturels du bois sur sa resistance à la pourriture. Bois et Forêts des Tropiques 191: 75–90.
• Keay, R.W.J., 1989. Trees of Nigeria. A revised version of Nigerian trees (1960, 1964) by R.W.J. Keay, C.F.A. Onochie and D.P. Stanfield. Clarendon Press, Oxford, United Kingdom. 476 pp.
• Neuwinger, H.D., 2000. African traditional medicine: a dictionary of plant use and applications. Medpharm Scientific, Stuttgart, Germany. 589 pp.
• Onguene, N.A. & Kuyper, T.W., 2001. Mycorrhizal associations in the rain forest of South Cameroon. Forest Ecology and Management 140: 277–287.
• Pennington, T.D., 1991. The genera of Sapotaceae. Royal Botanic Gardens, Kew, Richmond, United Kingdom and the New York Botanical Garden, New York, United States. 295 pp.
• Phongphaew, P., 2003. The commercial woods of Africa. Linden Publishing, Fresno, California, United States. 206 pp.
• Raponda-Walker, A. & Sillans, R., 1961. Les plantes utiles du Gabon. Paul Lechevalier, Paris, France. 614 pp.
• Terashima, H. & Ichikawa, M., 2003. A comparative ethnobotany of the Mbuti and Efe hunter-gatherers in the Ituri forest, Democratic Republic of Congo. African Study Monographs 24(1–2): 1–168.
Sources of illustration
• Aubréville, A., 1964. Sapotacées. Flore du Cameroun. Volume 2. Muséum National d’Histoire Naturelle, Paris, France. 143 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.H.M.J. Lemmens
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands


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
A. de Ruijter
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Correct citation of this article:
Lemmens, R.H.M.J., 2007. Autranella congolensis (De Wild.) A.Chev. 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 branch; 3, fruit; 4, seeds.
Redrawn and adapted by Iskak Syamsudin



bole and crown


bark


bark and slash


fruits and seed


wood


wooden panel


stacked planks


wood in transverse section


wood in tangential section


wood in radial section