Prota 7(1): Timbers/Bois d’œuvre 1
Fl. Congo Belge 3: 213 (1952).
Mimosaceae (Leguminosae - Mimosoideae)
Piptadenia leucocarpa Harms (1915).
Origin and geographic distribution
Newtonia leucocarpa occurs in Cameroon, Equatorial Guinea, Gabon, Congo and south-western DR Congo.
The wood (trade name: ossimiale) is suitable for construction, flooring, joinery, interior trim, ship building, vehicle bodies, mine props, furniture, cabinet work, handles, ladders, sporting goods, toys, novelties, agricultural implements, food containers, carvings, turnery, veneer and plywood.
Production and international trade
There are no statistics on production and international trade of Newtonia leucocarpa timber, but locally it has some importance, especially in Gabon.
The heartwood is silvery pink to reddish brown, often with wide darker veins, fairly distinctly demarcated from the narrow, paler sapwood. The grain is straight to wavy or interlocked, texture moderately coarse, but even. The wood is lustrous.
The wood is medium-weight to moderately heavy. At 12% moisture content, the density is 630–820 kg/m³. The wood should be dried carefully; logs should be quarter-sawn before drying and careful stacking is important to avoid serious degrade. The rates of shrinkage are rather high, from green to oven dry 3.7–4.4% radial and 6.7–8.6% tangential. Once dried the wood is moderately stable in service.
At 12% moisture content, the modulus of rupture is 132–198 N/mm², modulus of elasticity 10,300–15,500 N/mm², compression parallel to grain 52–74 N/mm², shear 7–13 N/mm², cleavage 10–27 N/mm and Chalais-Meudon side hardness 3.0–6.2.
The wood saws and works well, with moderate blunting effects on cutting edges. The use of a filler is needed to obtain a good finish, but then surfaces are very smooth and take a high polish. Moulding results are generally good, except in pieces of wood with interlocked grain. The wood holds screws and nails well, but pre-boring is recommended. The gluing properties are moderate. The wood is suitable for veneer production.
The wood is moderately durable. It showed moderate resistance to termite attack, but is susceptible to powder-post beetle, pinhole borer and marine borer attacks. The heartwood does not absorb preservatives, but the sapwood is only moderately resistant. Tests showed that the suitability of the wood for paper pulp production is only moderate.
Medium-sized to large tree up to 45 m tall; bole straight and cylindrical, branchless for up to 27 m but often less, up to 150 cm in diameter, at base with steep buttresses up to 2 m high; bark surface smooth to slightly fissured, greyish brown, inner bark pinkish brown to red, fibrous, with yellowish, translucent exudate; crown spreading, flat; young twigs hairy, soon becoming glabrous. Leaves alternate, bipinnately compound with (8–)10–12(–20) pairs of opposite pinnae; stipules linear-lanceolate, c. 3 mm long, caducous; petiole 0.5–1 cm long, rachis 5–14 cm long, grooved above, with a short gland between each pinna pair; leaflets opposite, 15–40 pairs per pinna, sessile, linear-oblong, 5–8 mm × 1–1.5 mm, asymmetrical at base, acute at apex, glabrous but sometimes slightly hairy at margin. Inflorescence an axillary or terminal spike-like false raceme, hairy, densely flowered. Flowers bisexual, regular, 5-merous, nearly sessile; calyx with c. 1.5 mm long tube, slightly toothed; petals free, elliptical, c. 2 mm long, hairy outside; stamens 10, free, anthers with gland at apex; ovary superior, hairy in upper part, style slender, curved. Fruit a flattened linear pod (10–)20–40 cm × 2–3 cm, at base with stipe up to 8.5 cm long, reddish brown, slightly transversely veined, dehiscent at one side. Seeds narrowly oblong, flat, 8–11 cm long including the papery wing surrounding the seed, brown, attached near one end. Seedling with hypogeal germination, with cotyledons remaining enclosed within the seed coat; first 2 leaves opposite, pinnately compound.
In Gabon flowers are produced at the beginning of the long dry season and fruits are mature around September. The winged seeds are mainly dispersed by wind.
Newtonia comprises about 15 species and is restricted to Africa. It seems related to Fillaeopsis from central Africa and Lemurodendron from Madagascar. Newtonia leucocarpa may be confused with Piptadeniastrum africanum (Hook.f.) Brenan, which differs in the absence of glands on the leaves, its glabrous ovary and its seeds being attached at the middle.
Newtonia glandulifera (Pellegr.) G.C.C.Gilbert & Boutique is a medium-sized to fairly large tree up to 40 m tall, with a similar distribution area as Newtonia leucocarpa. It differs in its larger leaflets, and seems to be less common in Gabon, but it is locally a common canopy tree in Bas-Congo (DR Congo). Its wood is suitable for similar purposes as that of Newtonia leucocarpa, but is heavier (about 900 kg/m³ at 12% moisture content) and tougher.
Newtonia griffoniana (Baill.) Baker f. resembles Newtonia glandulifera, but has rhombic leaflets (oblong to elliptical in Newtonia glandulifera). It is a medium-sized to fairly large forest tree up to 35 m tall, distributed from Nigeria to Gabon. Its wood is also suitable for similar purposes as that of Newtonia leucocarpa.
Newtonia duparquetiana (Baill.) Keay occurs in the same region as Newtonia griffoniana, but extends into the evergreen forests of West Africa to Sierra Leone. It is a medium-sized tree up to 30 m tall, characterized by 1–2 pairs of pinnae per leaf and 2 leaflets per pinna. It is occasionally felled for its brown, moderately heavy timber, e.g. in Sierra Leone and Gabon, but is generally too scarce to be important.
This is also the case for Newtonia aubrevillei (Pellegr.) Keay, which occurs rather scattered in evergreen forest from Sierra Leone to Ghana. It is a medium-sized tree with an often short and irregular bole, which has been felled in Liberia to make planks and canoes. The bark is used as an aphrodisiac. Its leaves are characterized by 3–4 pairs of pinnae, each with 3–4(–7) pairs of leaflets.
Newtonia elliotii (Harms) Keay is endemic to Sierra Leone, where it occurs in gallery forest. It is a small tree up to 15 m tall, with 2–4 pairs of obovate leaflets per pinna. It differs from Newtonia aubrevillei in having only 1 pair of pinnae per leaf. Its seeds have been used as a laxative.
Newtonia leucocarpa occurs in moist evergreen rainforest, mainly secondary forest.
Regeneration of Newtonia leucocarpa in natural forest in Bas-Congo Province of DR Congo was reported as fair. However, the common occurrence in secondary forest suggests that larger gaps are needed for good regeneration. In general, larger trees of Newtonia leucocarpa occur scattered, but sometimes in small groups. In Gabon the average bole volume has been recorded as 0.6 m³/ha. Freshly harvested logs are rather liable to insect attack and should be removed from the forest soon after felling to avoid damage to the wood.
Newtonia leucocarpa has a rather limited area of distribution in Central Africa, but is locally not uncommon, especially in western Gabon. It does not seem to be threatened at present, but some caution is needed to avoid over-exploitation.
There are certainly prospects for Newtonia leucocarpa on the timber market. This may offer possibilities for increased commercialization of the species, but research on growth rates, natural regeneration and the development of suitable management methods for forest in which it is a common constituent are needed to guarantee sustainable production in the future.
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Correct citation of this article:
Lemmens, R.H.M.J., 2008. Newtonia leucocarpa (Harms) G.C.C.Gilbert & Boutique. In: Louppe, D., Oteng-Amoako, A.A. & Brink, M. (Editors). Prota 7(1): Timbers/Bois d’œuvre 1. [CD-Rom]. PROTA, Wageningen, Netherlands.
base of bole
base of bole
fruits and seeds
wood in transverse section
wood in tangential section