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Combretum schumannii Engl.

Protologue
Pflanzenw. Ost-Afrikas C: 289 (1895).
Family
Combretaceae
Chromosome number
2n = 26
Synonyms
Combretum engleri Schinz (1901).
Vernacular names
Forest tree combretum, sand bushwillow (En). Mgurure, mpera-mwitu, mgongolo (Sw).
Origin and geographic distribution
Combretum schumannii occurs from southern Somalia and Kenya south to Namibia, Botswana, Zimbabwe, Mozambique and northern South Africa.
Uses
The wood is used for heavy construction, flooring, pestles, combs and carvings. It is suitable for interior trim, ship building, vehicle bodies, mine props, handles, ladders, sporting goods, musical instruments, pulley blocks, toys, novelties, precision equipment and turnery. In Namibia the branches of Combretum schumannii shrubs are used for making bows for children to practice hunting; they are not suited for bows for adults because they break too easily. The wood is also used as firewood and for charcoal production.
Bark and leaves are used in traditional medicine. Pulp made from the root bark is applied to swellings. Heated leaves are applied to the chest to treat pneumonia, and the leaves are also used to treat epilepsy and headache. The flowers are a source of nectar and pollen for honey bees. It has been reported that the tree gives mulch of good quality.
Production and international trade
In Kenya Combretum schumannii belongs to the four most commonly used species in the carving industry, together with Dalbergia melanoxylon Guill. & Perr., Brachylaena huillensis O.Hoffm. and Olea europaea L. subsp. cuspidata (Wall ex G.Don) Cif. However, there is no information on volume and price of wood in trade.
Properties
The heartwood is dark purplish brown when freshly sawn, slowly darkening to nearly black after years, and distinctly demarcated from the narrow, whitish sapwood. The grain is straight, texture moderately fine to fine, but not always even.
The wood is heavy, with a density of 1040–1120 kg/m³ at 12% moisture content. The wood air dries well but slowly, with little degrade. The rates of shrinkage are rather low, from green to 12% moisture content about 1% radial and 2–3% tangential. The wood is easy to work as long as sharp tools are used, and it takes a very nice polish. The turning properties are excellent. Pre-boring is necessary for nailing. The wood joints well. It is fairly durable, even in contact with the ground, and resists termite and marine borer attacks quite well. It cannot be impregnated with preservatives.
Adulterations and substitutes
The wood of Combretum schumannii has some resemblance to that of Dalbergia melanoxylon, which is also in high demand for carving. Ebony, the wood of Diospyros spp., is also used for similar purposes as that of Combretum schumannii.
Description
Deciduous shrub or small to medium-sized tree up to 20(–30) m tall; bole often crooked or fluted, up to 60(–80) cm in diameter; bark surface pale yellowish brown to brown, scaling off in large, elongate flakes, inner bark pinkish with paler streaks, exuding a thick whitish sap; crown open; twigs slender, nearly glabrous. Leaves opposite, simple and entire; stipules absent; petiole up to 1 cm long, slender; blade elliptical to oblong-elliptical, ovate or obovate, (2–)6–12(–15) cm × (1–)2–4.5(–7.5) cm, cuneate to rounded at base, rounded to obtuse or short-acuminate at apex, papery, slightly warty and scaly, pinnately veined with 3–8 pairs of lateral veins. Inflorescence a short axillary spike up to 1.5 cm long, sticky. Flowers bisexual, regular, 4-merous, pale yellow, scented, sessile; receptacle consisting of 2 parts, lower part 1–1.5 mm long, upper part 1.5–2.5 mm long, with 4 pouch-like swellings; sepals shallowly triangular, indistinct; petals free, nearly orbicular, 1.5–2 mm long, glabrous; stamens 8, free, c. 5 mm long; ovary inferior, 1-celled, style c. 5 mm long. Fruit a 4-winged nut, ovoid to nearly orbicular in outline, 3–4 cm long, with 1–2 cm long stipe and c. 1 cm broad wings, green turning pale brown, indehiscent, 1-seeded. Seedling with epigeal germination, with sessile kidney-shaped cotyledons.
Other botanical information
Combretum is a very large genus, comprising about 250 species and distributed worldwide in the tropics and subtropics. About 140 species occur in tropical Africa. In several African floras, Combretum engleri Schinz from the western part of southern Africa has been included in the synonymy of Combretum schumannii, although the former is only a shrub up to 4 m tall with smaller leaves and fruits. More research is needed to elucidate the status of Combretum engleri; it might be a separate taxon (either on specific or infraspecific level), or the differences might be due to climatic conditions.
Combretum kraussii Hochst. occurs in eastern South Africa and Swaziland, but a few specimens have been collected in southern Mozambique. It is a shrub or small tree up to 12 m tall. Its yellow wood with usually straight grain and fine texture is suitable for flooring, joinery, mine props, ship building, vehicle bodies, furniture, cabinet work, handles, ladders, sporting goods, toys, novelties, agricultural implements and turnery; it is also used as firewood. At 12% moisture content, the density of the wood is about 770 kg/m³, modulus of rupture 110 N/mm², modulus of elasticity 13,230 N/mm² and compression parallel to grain 63 N/mm². Although the wood is hard and tough, it is moderately easy to work; it polishes well. It is only moderately durable, and resistant to impregnation by preservatives. The roots of Combretum kraussii are used in traditional medicine to treat wounds, and as an anodyne, tonic and appetite stimulant. The pliable young stems are used in basket making.
Anatomy
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; 23: shape of alternate pits polygonal; 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; 41: mean tangential diameter of vessel lumina 50–100 μm; (45: vessels of two distinct diameter classes, wood not ring-porous); 47: 5–20 vessels per square millimetre; 58: gums and other deposits in heartwood vessels. Tracheids and fibres: 60: vascular/vasicentric tracheids present; 61: fibres with simple to minutely bordered pits; 66: non-septate fibres present; 70: fibres very thick-walled. Axial parenchyma: 83: axial parenchyma confluent; 92: four (3–4) cells per parenchyma strand. Rays: 97: ray width 1–3 cells; (104: all ray cells procumbent); (109: rays with procumbent, square and upright cells mixed throughout the ray); 115: 4–12 rays per mm; 116: 12 rays per mm. Mineral inclusions: 156: crystals in enlarged cells.
(P. Détienne & P. Baas)
Growth and development
In Namibia the flowers only last for about 3 weeks, from mid September until the beginning of October, when the shrub is nearly leafless. The flowers are pollinated by insects such as honey bees. Fruits ripen about 7 months after flowering. Monkeys have been reported to feed on the fruits and may serve as seed dispersers.
Ecology
Combretum schumannii occurs in a wide range of habitats, from lowland rainforest to riverine forest, dry deciduous forest and wooded savanna, from sea-level up to 1150(–1600) m altitude. In southern Africa it is commonly found on Kalahari sand and rocky outcrops.
Propagation and planting
Seeds should be sown while still fresh. Germination can be fast and the germination rate high. Whole fruits can be stored for a few weeks only without affecting the germination capacity of the seed. It has been recommended to strip off the wings of the fruit before sowing. Trees may produce root suckers that can be used for propagation.
Management
The trees can be managed by coppicing and lopping.
Handling after harvest
The boles are usually short and commonly fluted, which reduces the possibilities of usage for sawn wood.
Genetic resources
Combretum schumannii is widespread and at least locally common. This makes that it is not easily liable to genetic erosion. However, in some regions, e.g. in coastal regions in Kenya, Combretum schumannii trees are selectively felled for their wood that is highly valued for carving, thereby affecting populations of larger-sized trees. Studies on the genetic variability are warranted, covering populations all over the distribution area; this may also elucidate the status of Combretum engleri.
Prospects
There is no information on growth rates and natural regeneration of Combretum schumannii. Research is needed to develop models for sustainable harvesting of its wood. It does not seem to be a serious candidate for planting with the objective of economically viable timber production because the bole is often of too small size and poor shape, and because growth is probably slow.
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.
• Bryce, J.M., 1967. The commercial timbers of Tanzania. Tanzania Forest Division, Utilisation Section, Moshi, Tanzania. 139 pp.
• Exell, A.W., 1978. Combretaceae. In: Launert, E. (Editor). Flora Zambesiaca. Volume 4. Flora Zambesiaca Managing Committee, London, United Kingdom. pp. 100–183.
• Lovett, J.C., Ruffo, C.K., Gereau, R.E. & Taplin, J.R.D., 2006. Field guide to the moist forest trees of Tanzania. [Internet] Centre for Ecology Law and Policy, Environment Department, University of York, York, United Kingdom. http://celp.org.uk/ projects/ tzforeco/. Accessed June 2008.
• Maundu, P. & Tengnäs, B. (Editors), 2005. Useful trees and shrubs for Kenya. World Agroforestry Centre - East and Central Africa Regional Programme (ICRAF-ECA), Technical Handbook 35, Nairobi, Kenya. 484 pp.
• Mbuya, L.P., Msanga, H.P., Ruffo, C.K., Birnie, A. & Tengnäs, B., 1994. Useful trees and shrubs for Tanzania: identification, propagation and management for agricultural and pastoral communities. Technical Handbook 6. Regional Soil Conservation Unit/SIDA, Nairobi, Kenya. 542 pp.
• Wimbush, S.H., 1957. Catalogue of Kenya timbers. 2nd reprint. Government Printer, Nairobi, Kenya. 74 pp.
Other references
• Beentje, H.J., 1994. Kenya trees, shrubs and lianas. National Museums of Kenya, Nairobi, Kenya. 722 pp.
• Coates Palgrave, K., 1983. Trees of southern Africa. 2nd Edition. Struik Publishers, Cape Town, South Africa. 959 pp.
• Dale, I.R. & Greenway, P.J., 1961. Kenya trees and shrubs. Buchanan’s Kenya Estates Limited, Nairobi, Kenya. 654 pp.
• Kokwaro, J.O., 1993. Medicinal plants of East Africa. 2nd Edition. Kenya Literature Bureau, Nairobi, Kenya. 401 pp.
• Leger, S., 1997. The hidden gifts of nature: A description of today’s use of plants in West Bushmanland (Namibia). [Internet] DED, German Development Service, Windhoek, Namibia & Berlin, Germany. http://www.sigridleger.de/book/. Accessed June 2008.
• Msangi, T.H., 1991. The medicinal plants of Tanzania as a genetic resource. A survey and assessment of conservation strategies. MSc thesis, School of Biological Sciences, University of Birmingham, Birmingham, United Kingdom. 96 pp.
• Neuwinger, H.D., 2000. African traditional medicine: a dictionary of plant use and applications. Medpharm Scientific, Stuttgart, Germany. 589 pp.
• Takahashi, A., 1978. Compilation of data on the mechanical properties of foreign woods (part 3) Africa. Shimane University, Matsue, Japan, 248 pp.
• Teel, W., 2004. Tree profile: Combretum schumannii. [Internet]. http://agroforesttrees.cisat.jmu.edu/ tree_info.asp?tid=33. Accessed June 2008.
• Thulin, M., 1993. Combretaceae. In: Thulin, M. (Editor). Flora of Somalia. Volume 1. Pteridophyta; Gymnospermae; Angiospermae (Annonaceae-Fabaceae). Royal Botanic Gardens, Kew, Richmond, United Kingdom. pp. 247–254.
• Wickens, G.E., 1973. Combretaceae. In: Polhill, R.M. (Editor). Flora of Tropical East Africa. Crown Agents for Oversea Governments and Administrations, London, United Kingdom. 99 pp.
Sources of illustration
• Exell, A.W., 1978. Combretaceae. In: Launert, E. (Editor). Flora Zambesiaca. Volume 4. Flora Zambesiaca Managing Committee, London, United Kingdom. pp. 100–183.
• Maundu, P. & Tengnäs, B. (Editors), 2005. Useful trees and shrubs for Kenya. World Agroforestry Centre - East and Central Africa Regional Programme (ICRAF-ECA), Technical Handbook 35, Nairobi, Kenya. 484 pp.
Author(s)
D. Dongock Nguemo
Département des Sciences Biologiques, Faculté des Sciences, Université de Ngaoundéré, BP 454, Ngaoundéré, Cameroon


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-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

Correct citation of this article:
Dongock Nguemo, D., 2009. Combretum schumannii Engl. In: Lemmens, R.H.M.J., Louppe, D. & Oteng-Amoako, A.A. (Editors). Prota 7(2): Timbers/Bois d’œuvre 2. [CD-Rom]. PROTA, Wageningen, Netherlands.
Distribution Map wild


1, tree habit; 2, leafy twig; 3, flower in longitudinal section; 4, fruit.
Redrawn and adapted by Achmad Satiri Nurhaman