Dilobeia thouarsii

Family

Proteaceae

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Chromosome number

2n = 52

Synonyms

Vernacular names

Origin and geographic distribution

Dilobeia thouarsii is endemic to Madagascar, where it is widespread in the eastern parts of the island and occurs locally in the central regions.

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Uses

The wood, most commonly known as ‘vivaona’, is widely used in house construction, and for joinery and railway sleepers. It was popular for parts of wagons such as hubs, felloes and spokes. It is suitable for hydraulic works in fresh water, mine props, vehicle bodies, furniture, sporting goods, toys, novelties, agricultural implements and turnery. It is not recommended for flooring because of its high shrinkage rates. Branches are used as firewood and the wood produces a good charcoal.
Oil is extracted from the seeds. It is used as cooking oil, but only in times of scarcity of regular cooking oil because it has a slightly disagreeable taste. It is more commonly used as cosmetic, in soap production and for illumination. The bark is used in traditional medicine. It has emetic properties and bark decoctions are administered to treat gonorrhoea, and as diuretic and vermifuge.

Production and international trade

The wood of Dilobeia thouarsii is commonly used locally, but not traded on the international timber market.

Properties

The heartwood is yellowish brown to pale reddish brown and indistinctly demarcated from the narrow and slightly paler sapwood. The grain is straight to slightly interlocked, texture coarse and rather uneven. Fresh wood is somewhat oily to the touch.
The wood is heavy, with a density of 940–1070 kg/m³ at 12% moisture content. It air dries slowly and great care is needed to avoid excessive distortion and splitting. It is recommended to quarter-saw logs before drying. The rates of shrinkage are high to very high, from green to oven dry 6.8–9.5% radial and 9.8–15.0% tangential. Once dry, the wood is unstable in service. At 12% moisture content, the modulus of rupture is 196–255 N/mm², modulus of elasticity 18,030–22,850 N/mm², compression parallel to grain 82–104 N/mm², shear 7–11 N/mm², cleavage 20–32 N/mm and Chalais-Meudon side hardness 6.9–11.4.
The wood is rather difficult to saw and work because of its high density; machine tools are needed. It can be planed to a smooth finish and polishes well. The nailing and screwing properties are moderate; the wood is liable to split and pre-boring is needed. The use of a filler is recommended to obtain a good finish. The gluing properties are usually satisfactory and turning properties good. The wood paints satisfactorily, and is not suitable for slicing and peeling. It is fairly durable, being moderately resistant to fungi and resistant to termites, but susceptible to marine borer attack. The sapwood is liable to Lyctus attack. The heartwood can be treated with preservatives under pressure with satisfactory results.
Wood dust may cause irritation to eyes and mucous membranes; this is reportedly due to the presence of a whitish irritant substance in the vessels.
The seeds contain 60–65% of a brownish yellow oil with a characteristic strong smell that disappears rapidly upon cooking. The oil has a solidification point of 15°C. The main fatty acids are oleic acid (about 72%), stearic acid (12%) and palmitic acid (6%).

Description

Dioecious, evergreen, small to medium-sized tree up to 20(–30) m tall; bole branchless for up to 15 m, usually straight, up to 80 cm in diameter; bark surface scaly, reddish brown, inner bark reddish brown with blackish spots; branches thick, with distinct leaf scars, twigs densely reddish to greyish short-hairy. Leaves arranged spirally near tips of branches, simple; stipules absent; petiole up to 11 cm long; blade heart-shaped, 7.5–20(–25) cm × 5–15(–19) cm, cuneate at base, with 2 large, rounded lobes at apex, with a gland between the lobes at the end of the midrib, leathery, glabrous, midrib branching into 3 main veins at 1.5–5 cm from the base, finer venation distinct at lower leaf surface. Inflorescence axillary, densely short-hairy, male one a many-flowered panicle up to 15 cm long, female one a short raceme up to 6 cm long. Flowers unisexual, regular, with 4 free elliptical-oblong tepals 4–6 mm long, hairy outside, caducous; male flowers sessile, with 4 free stamens opposite the tepals and rudimentary ovary; female flowers with short pedicel, 4 rudimentary stamens and superior, globose, hairy, 1-celled ovary 2.5–4 mm in diameter, style very short, stigma large and deeply 2-lobed. Fruit an ellipsoid drupe 3–4 cm × 2–2.5 cm, with 4 low ridges, pale brown short-hairy but becoming glabrous when mature, with thin layer of fleshy pulp and bony stone, 1-seeded. Seed with thick, oily cotyledons.

Other botanical information

Dilobeia comprises only 2 species, with Dilobeia tenuinervis Bosser & R.Rabev. only known from forest near Taolañaro. The heart-shaped persistent leaves are very characteristic for Dilobeia thouarsii.

Anatomy

Wood-anatomical description (IAWA hardwood codes):
Growth rings: 2: growth ring boundaries indistinct or absent. Vessels: 5: wood diffuse-porous; 9: vessels exclusively solitary (90% or more); 13: simple perforation plates; 22: intervessel pits alternate; 24: intervessel pits minute (≤ 4 μm); 30: vessel-ray pits with distinct borders; similar to intervessel pits in size and shape throughout the ray cell; (42: mean tangential diameter of vessel lumina 100–200 μm); 43: mean tangential diameter of vessel lumina ≥ 200 μm; 46: ≤ 5 vessels per square millimetre. Tracheids and fibres: (61: fibres with simple to minutely bordered pits); (62: fibres with distinctly bordered pits); (63: fibre pits common in both radial and tangential walls); 66: non-septate fibres present; 70: fibres very thick-walled. Axial parenchyma: (76: axial parenchyma diffuse); 80: axial parenchyma aliform; 82: axial parenchyma winged-aliform; 83: axial parenchyma confluent; 84: axial parenchyma unilateral paratracheal; 92: four (3–4) cells per parenchyma strand; 93: eight (5–8) cells per parenchyma strand. Rays: 97: ray width 1–3 cells; (98: larger rays commonly 4- to 10-seriate); 104: all ray cells procumbent; 106: body ray cells procumbent with one row of upright and/or square marginal cells; 115: 4–12 rays per mm.
(F.D. Kamala, P. Baas & P.E. Gasson)

Growth and development

Leaves of young plants of Dilobeia thouarsii are quite distinct from those of older trees; they have 2 or 4 narrow lobes up to 30(–50) cm long. Trees flower from October to March and fruits can be found nearly throughout the year, although they seem to ripen only in November to January.

Ecology

Dilobeia thouarsii occurs in humid evergreen forest from sea-level up to 1800 m altitude, but most commonly at 700–1300 m. It is locally abundant.

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Harvesting

Felling the trees with their dense and hard wood requires special equipment, and the heavy logs are not easy to transport.

Handling after harvest

The fruit stones are pounded with a mortar and the fragments are boiled in a small amount of water. The oil is collected from the surface of the liquid.

Genetic resources and breeding

Dilobeia thouarsii is widespread in eastern Madagascar and locally common. There are no indications that it is in immediate danger of genetic erosion, although the splitting up of forest in its area of distribution may threaten it in the near future.

Prospects

Dilobeia thouarsii is valued by the local people, mainly for its strong and durable wood and for its oil-rich seeds. Little is known about its growth rates and propagation, and research is warranted to be able to draw up recommendations for sustainable exploitation.

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.
• Bosser, J. & Rabevohitra, R., 1991. Proteacées (Proteaceae). Flore de Madagascar et des Comores, familles 45, 57, 93 bis, 94, 107 bis. Muséum National d’Histoire Naturelle, Paris, France. pp. 47–69.
• Decary, R., 1946. Plantes et animaux utiles de Madagascar. Annales du Musée Colonial de Marseille, 54e année, 6e série, 4e volume, 1er et dernier fascicule. 234 pp.
• Guéneau, P., Bedel, J. & Thiel, J., 1970–1975. Bois et essences malgaches. Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 150 pp.
• Parant, B., Chichignoud, M. & Rakotovao, G., 1985. Présentation graphique des caractères technologiques des principaux bois tropicaux. Tome 5. Bois de Madagascar. CIRAD, Montpellier, France et Département des Recherches forestières et piscicoles du FOFIFA, Antananarivo, Madagascar. 162 pp.
• Ralaibiharison, A.B.J.M., 1995. Contribution à l’étude de la fraction lipidique de Dilobeia thouarsii (Proteaceae). Mémoire de fin d’étude Ecole Supérieure des Sciences Agronomiques, Département Industrie agricoles et alimentairesaux Forêt, Université d’Antananarivo, Madagascar. 70 pp.
• Schatz, G.E., 2001. Generic tree flora of Madagascar. Royal Botanic Gardens, Kew, Richmond, United Kingdom. 477 pp.
• Takahashi, A., 1978. Compilation of data on the mechanical properties of foreign woods (part 3) Africa. Shimane University, Matsue, Japan. 248 pp.

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Other references

• Boiteau, P., Boiteau, M. & Allorge-Boiteau, L., 1999. Dictionnaire des noms malgaches de végétaux. 4 Volumes + Index des noms scientifiques avec leurs équivalents malgaches. Editions Alzieu, Grenoble, France.
• Brown, K.A., Ingram, J.C., Flynn, D.F.B., Razafindrazaka, R. & Jeannoda, V., 2009. Protected area safeguard tree and shrub communities from degradation and invasion: a case study in eastern Madagascar. Environmental Management 44: 136–148
• Guéneau, P. & Guéneau, D., 1969. Propriétés physiques et mécaniques des bois malgaches. Cahiers scientifiques No 2, Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 51 pp.
• Kubitzki, K., 2007. Families and genera of vascular plants. Vol. 9. Flowering plants, Eudicots. Springer, Berlin, Germany. 509 pp.
• Lanyon, J.W., 1979. The wood anatomy of three proteaceous timbers: Placospermum coriaceum, Dilobeia thouarsii and Garnieria spathulaefolia. IAWA Bulletin No 2–3: 27–33.
• Rakotovao, G., Rabevohitra, R., Gerard, J., Détienne, P. & Collas de Chatelperron, P., en préparation. Atlas des bois de Madagascar. FOFIFA-DRFP, Antananarivo, Madagascar.
• Sallenave, P., 1955. Propriétés physiques et mécaniques des bois tropicaux de l’Union française. Centre Technique Forestier Tropical, Nogent sur Marne, France. 129 pp.
• Sallenave, P., 1971. Propriétés physiques et mecaniques des bois tropicaux. Deuxième supplément. Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 128 pp.

Afriref references

Sources of illustration

• Schatz, G.E., 2001. Generic tree flora of Madagascar. Royal Botanic Gardens, Kew, Richmond, United Kingdom. 477 pp.

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Author(s)

•	S. Rakotonandrasana Centre National d’Application des Recherches Pharmaceutiques, B.P. 702, 101 Antananarivo, Madagascar

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 105 / D (Bât. C, Bur. 113), 34398 Montpellier Cédex 5, France
•	A.A. Oteng-Amoako Forestry Research Institute of Ghana (FORIG), University P.O. Box 63, KNUST, Kumasi, Ghana

Associate editors

•	E.A. Obeng Forestry Research Institute of Ghana (FORIG), University P.O. Box 63, KNUST, Kumasi, Ghana

Photo editor

•	G.H. Schmelzer PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Correct citation of this article

Rakotonandrasana, S., 2011. Dilobeia thouarsii Roem. & Schult. [Internet] Record from PROTA4U. Lemmens, R.H.M.J., Louppe, D. & Oteng-Amoako, A.A. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands. <http://www.prota4u.org/search.asp>. Accessed .

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