Prota 7(1): Timbers/Bois d’œuvre 1
Adansonia 9: 294 (1870).
Papilionaceae (Leguminosae - Papilionoideae, Fabaceae)
Origin and geographic distribution
Xanthocercis madagascariensis is endemic to Madagascar, where it mainly occurs in the northern half.
The wood is used sometimes as a substitute of the wood of Guaiacum officinale L. for luxury furniture, exterior and interior joinery, luxury flooring, and in boat construction. It is also used for wood carving, and for making butcher’s blocks, pulleys and luxury decorative handles of brushes and implements. The wood is suitable for mine props, vehicle bodies, musical instruments, toys and novelties, turnery, draining boards and pattern making. It is popular for poles that are durable in contact with the ground. The wood is used as firewood and for making charcoal. The fruit pulp is edible.
The heartwood is beige-brown to brown, often with lighter patches and dark streaks, and distinctly demarcated from the 6–8 cm wide and paler sapwood. The grain is often wavy, texture fine and even. The wood is very heavy, with a density of 1020–1230 kg/m³ at 12% moisture content. The rates of shrinkage during drying are high: from green to oven dry 6.0–7.7% radial and 11.0–13.7% tangential. The wood is hard. At 12% moisture content, the modulus of rupture is 180–202 N/mm², modulus of elasticity 14,600–17,400 N/mm², compression parallel to grain 74–91 N/mm², shear 11.3–12.3 N/mm², cleavage 36–43 N/mm and Chalais-Meudon side hardness 10.9–12.4.
The wood is rather difficult to saw, requiring much power and dulling sawteeth rapidly. It is difficult to work, and nailing is almost impossible without pre-boring. The wood finishes well. Staining and polishing give very good results. The heartwood is durable and resistant to fungi, termites and marine borers. The sapwood, however, is liable to blue stain and not durable. The sawdust irritates mucous membranes and protective measures are needed during sawing operations.
Deciduous small to fairly large tree up to 30 m tall; bole straight and cylindrical, branchless for up to 10 m and up to 80 cm in diameter; bark smooth with many lenticels, becoming flaky. Leaves alternate, imparipinnately compound with (5–)7–9(–10) leaflets; petiole and rachis glabrous; leaflets alternate, ovate to oblong-ovate, 3–8 cm × 2–5 cm, rounded shallowly cordate at base, acuminate at apex, thinly leathery, glabrous. Inflorescence an axillary or terminal raceme, often branched and combined into a terminal panicle, many-flowered. Flowers bisexual, papilionaceous; pedicel with 2 small bracteoles; calyx broadly cup-shaped, 3–4 mm long, truncate at apex, densely yellowish hairy; corolla creamy to pinkish, with oblong standard c. 1 cm × 0.5 cm, shortly clawed at base, upcurved, wing and keel petals similar, narrowly oblong, all 5 petals with a yellowish hairy stripe outside; stamens 10, fused at extreme base; ovary superior, shortly stalked, shortly hairy, 1-celled, style short, stigma indistinct. Fruit a drupe-like ellipsoid pod 2.5–5(–9) cm × 1.5–2.5 cm, slightly constricted between the seeds, glabrous, smooth, indehiscent, 1–2(–3)-seeded, with seeds enclosed in a fibrous pulp. Seeds kidney-shaped, 1.5–2.5 cm × 1–1.5 cm, dark brown.
Xanthocercis madagascariensis can fix atmospheric nitrogen by symbiosis with rhizobia.
Xanthocercis comprises 3 species: one in Madagascar, one in Gabon and one in southern Africa. It is related to Angylocalyx.
Xanthocercis madagascariensis closely resembles Xanthocercis rabiensis Maesen from Gabon, which differs in having up to 5 leaflets per leaf and greyish hairy calyx. Xanthocercis rabiensis is a large tree up to 40 m tall with a cylindrical bole up to 300 cm in diameter, known only from a few specimens. Its wood is slightly lighter in weight than that of Xanthocercis madagascariensis, with a density of 950–990 kg/m³ at 12% moisture content. Xanthocercis rabiensis is classified as vulnerable in the IUCN Red list of threatened species.
Xanthocercis zambesiaca (Baker) Dumaz-le-Grand (nyala tree) occurs in southern Africa. Its wood is occasionally used although it strongly irritates nose and throat during working, but the use of its edible fruits is more important.
Xanthocercis madagascariensis occurs in deciduous and evergreen forest up to 400 m altitude. It can be found on sandy soils, but also on limestone outcrops and basaltic soils.
Genetic resources and breeding
Xanthocercis madagascariensis is classified as vulnerable in the IUCN Red list of threatened species. It is felled selectively for its timber and this makes it liable to genetic erosion, although it is fairly widely distributed and occurs within some protected areas.
Xanthocercis madagascariensis is an interesting timber tree reaching fair dimensions and providing excellent-quality timber. However, logging in the remaining natural populations should be done with great care as the species has already become vulnerable. Tests on planting Xanthocercis madagascariensis in Madagascar seem worthwhile to determine its potential as a plantation timber tree. However, slow growth is likely, comparable to Xanthocercis rabiensis, for which a mean annual diameter growth of 4 mm has been recorded under natural growing conditions.
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Correct citation of this article:
Lemmens, R.H.M.J., 2007. Xanthocercis madagascariensis Baill. In: Louppe, D., Oteng-Amoako, A.A. & Brink, M. (Editors). Prota 7(1): Timbers/Bois d’œuvre 1. [CD-Rom]. PROTA, Wageningen, Netherlands.