Afzelia africana Sm. ex Pers. is a tropical African tree, medium to large, deciduous, up to 40 m high. It is mostly used for its high-grade timber but has good potential to provide fodder for livestock and food. Afzelia africana is a multipurpose tree suitable for use in agroforestry systems. It has been considered to be vulnerable because of pressure put by wood exploitation but also because of poor regeneration of stands due to browsing animals or intensive lopping.
Morphology
Afzelia africana can grow up to 30-40 m high in forests and up to 10-18 m in savannah (Orwa et al., 2009). It is taprooted but also develops secondary roots that explore the first centimetres of the soil (Bationo et al., 2011). The trunk has small unequal buttresses at his base (Gérard et al., 2011; Orwa et al., 2009). The trunk is straight, cylindrical, branchless up to 20 m high and can reach 1-1.8 m in diameter above buttresses (Donkpegan et al., 2014). The bark is 2 cm thick, scaly, very aromatic, grey to dark brown in colour. The crown is large, spreading. Its shape (flat or rounded) depends on age and growing conditions (Gérard et al., 2011; Orwa et al., 2009). The branches are tortuous, more or less upright, branchlets are glabrous with lenticels.The leaves are alternate, petiolated, paripinnate, up to 30 cm long with 7-17 pairs of leaflets. The leaflets are opposite, elliptic to ovate-elliptic in shape, 5-15 cm long x 3-8.5 cm broad. The inflorescence is a terminal or axillary panicle, 3-13 cm long. The flowers are sweet scented, white to yellowish, zygomorphous bearing 5 petals among which one is 1.5 cm x 1 cm, red striped, and the other 4 are very minute. Afzelia africana flowers in the rainy season.
The fruit requires 6 months to ripen. It is an oblong, straight flattened, dehiscent pod, 10-20 cm long x 5-8 cm broad, brown to black in colour. Pods can remain on the tree 6 months after ripening. Each pod contains several potentially toxic seeds, 2-3 cm long, inserted in a conspicuous edible bright orange aril covering one third of their length. The other 2/3 of the seed are black. Seeds are spread by birds which feed on the arils (Gérard et al., 2011).
Uses
Afzelia africana is considered to be one ot the most important woody fodder plant in many parts of Africa. Its foliage is reported to be good for cattle particularly during the dry season and the beginning of the rainy season when grass has not grown yet and other forages are rare (Gérard et al., 2011; Ikhimioya et al., 2007).
Afzelia africana leaves, fruits and seeds are browsed by wildlife animals, and many parts of the tree are edible. The leaves can be cooked and used as vegetables while young leaves are mixed with ground cereals before cooking. The flowers are used as condiment in sauces and the seed aril is reported to be sweet. The seed is rich in protein and oil. It is possible to make flour out the seed and to use it in mixture with wheat flour in order to increase protein value (Gérard et al., 2011; Ejikeme et al., 2010). Due to the presence of a water-soluble gum (xyloglucan), the seed is used as a thickening agent for soup in South-Eastern parts of Nigeria though it is reported to have some toxicity (Igwenyi et al., 2010).
The oil has long shelf-life, contains valuable PUFA (polyunsaturated fatty acids) and can be used for cooking (Gérard et al., 2011; Ejikeme et al., 2010). The oil of Afzelia africana is reported to be a semi-drying oil that can have industrial applications in surface coatings of alkyd resins (Gérard et al., 2011; Ejikeme et al., 2010). The coproduct of oil extraction is a seed cake that can be fed to livestock.
Afzelia africana is mainly used for its heavy wood, which is light brown to red brown in colour, durable, termite-proof, and of high quality (dimensional stability and durability). It does not require treatment prior to usage in permanent humid conditions or in places where insects are abundant. It can compare to high grade timbers like teak or merbau and is used for carpentry, canoes, house building, panelling, parquet floors, doors, frames stairs and many types of furniture and kitchen utensils. Afzelia Africana wood makes good firewood and charcoal. It is used as an ornamental and for rituals, and considered a fetish tree in many regions (Gérard et al., 2011).
This species has been considered vulnerable due to the pressure put by wood exploitation (IUCN, 1998).
