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Eucalyptus tereticornis Sm.

Protologue
Spec. bot. New Holland 4: 41 (1795).
Family
Myrtaceae
Chromosome number
2n = 22
Vernacular names
Forest red gum, blue gum, Queensland blue gum (En). Eucalyptus bleu (Fr). Eucalipto de opérculo rostrado (Po). Mkaratusi (Sw).
Origin and geographic distribution
Eucalyptus tereticornis has an extensive natural distribution in a long strip about 100 km wide, from southern Papua New Guinea and the northern tip of Queensland to southern Victoria along the east coast of Australia. It was one of the first eucalypts exported from Australia and is now cultivated throughout the tropics, on a large scale in India and Brazil. It was introduced into Ethiopia in 1895, into Zimbabwe in 1900 and into Uganda in 1912, and it has been planted throughout tropical Africa.
Uses
The wood is used for construction, railway sleepers, bridges, wharves, poles, piles, posts, boats, mine props, boxes, hardboard and particle board. Furthermore, it is suitable for flooring, vehicle bodies, furniture, handles, ladders, sporting goods, agricultural implements, veneer, plywood, core stock, matches, joinery, vats, toys, novelties, turnery and wood-wool. The wood is used for paper making. It is a source of fuelwood and charcoal.
Eucalyptus tereticornis is a major source of pollen and nectar, producing a caramel-flavoured honey. The leaves are one of the sources of eucalypt oil. Eucalyptus tereticornis is used for reforestation, shelter-belts and shade. A decoction of the leaf serves to reduce fever and alleviates pulmonary problems.
Production and international trade
For the year 1995 it was estimated that worldwide Eucalyptus plantations amounted to 14.6 million ha, of which 1.8 million ha in Africa. Eucalyptus tereticornis is among the more commonly planted Eucalyptus species throughout the world. It is, therefore, most likely that saw and veneer logs and pulp of Eucalyptus tereticornis are internationally marketed, but specific information is lacking. In India over 500,000 ha have been planted, and in Brazil about 250,000 ha.
Properties
The heartwood is pale to dark red, and fairly well demarcated from the grey to cream-coloured sapwood. The grain is wavy or interlocked, texture even and fairly fine.
The wood has a density of 660–1060 kg/m³ at 12% moisture content, but wood from plantations often has a lower density than that from natural stands. The rates of shrinkage from green to oven dry are high: 4.2–10.6% radial and 7.4–13.5% tangential. The wood has a strong tendency to warp during drying. It is not stable in service.
The wood is strong, tough and hard. At 12% moisture content, the modulus of rupture is 118–181 N/mm², modulus of elasticity 8400–15,200 N/mm², compression parallel to grain 49–72 N/mm², shear 6–11 N/mm², cleavage 26–27 N/mm and Chalais-Meudon side hardness 2.7–8.7.
The wood saws well and works well with hand and machine tools, but it splits easily and the presence of interlocked grain makes it somewhat difficult to finish. It holds nails well and glues well.
The wood is durable and has good weathering and wearing properties. In Australia the wood is one of the most resistant to marine borer attack, but it failed after 2.5–10 years at the Pacific coast of the United States. The sapwood is susceptible to Lyctus borers. The heartwood is resistant to impregnation with preservatives, the sapwood is permeable.
The energy value of the wood is 17,750–22,000 kJ/kg. The wood yields a very good-quality pulp. The wood fibres in Sudanese material are on average 0.80 mm long, with a diameter of 14.2 μm, a cell wall thickness of 4.5 μm and a lumen diameter of 5.2 μm. The average chemical composition of the oven-dry wood is: cellulose 45–48%, pentosans 11–23%, lignin 22–30%, ash 0.5–1.3%. The solubility in hot water is 3–5%, in alcohol-benzene 1–4%, in 1% NaOH 15–19%. Pulping of Sudanese material with various chemical processes gave yields of 43–46% of pulp with good mechanical properties. The wood contains 0.5% essential oil and 6–12% tannin; the bark contains 3–15% tannin.
The leaves yield 0.45–3.4% essential oil. The oil composition varies strongly, and various chemotypes have been distinguished: the cineole chemotype (containing 20–62% 1, 8-cineole), the p-cymene chemotype (up to 29% p-cymene, small amounts of 1,8-cineole and pinenes), the β-pinene chemotype (with up to 40% β-pinene) and the farnesol chemotype (up to 56.5% (E,E)-farnesol). The essential oil has shown antibacterial and antifungal activities, and in-vivo analgesic, muscle-relaxant and anti-inflammatory effects in rats and mice. The essential oil also showed insecticidal activity, e.g. against the malaria vector Anopheles stephensi. Methanolic extracts of the leaves exhibited in-vitro antihyperglycaemic effects in mice.
Botany
Evergreen, large tree up to 50 m tall; bole relatively short, straight, up to 200 cm in diameter; bark surface white, grey or grey-blue, decorticating over the whole trunk in large plates or flakes to leave a smooth or mat, mottled surface; crown fairly open. Leaves simple and entire; stipules absent; petiole 1–3 cm long, rounded or channelled; blade narrowly lanceolate to lanceolate, 10–21 cm × 1–3(–5) cm, acuminate at apex, glabrous, shiny green, pinnately veined, aromatic when crushed. Inflorescence an axillary, solitary, condensed and reduced, umbel-like dichasium, 3–12-flowered; peduncle rounded or angular, 5–25 mm long. Flowers bisexual, regular, white; pedicel 2–10 mm long; flower buds divided into a hemispherical hypanthium (lower part) 2–3 mm × 4–6 mm, and conical operculum (upper part) 8–13 mm × 4–6 mm and shed at anthesis; stamens numerous; ovary inferior, 4–5-celled. Fruit a thin-walled globular to ovoid capsule, 5–9 mm × 4–10 mm, enclosed in a woody hypanthium, opening with (2–)4–5 strongly exserted valves, many-seeded. Seeds rough, brown-black. Seedling with epigeal germination; cotyledons 2-lobed; first 2–4 leaves opposite.
In plantations Eucalyptus tereticornis starts flowering when 2–6 years old, but in Brazil 2-month-old seedlings have been observed flowering. Small clusters of white flowers appear every year, but heavy blooming occurs only once every 3–4 years. In Nairobi (Kenya) 41-year-old trees had reached an average height of 29 m and an average bole diameter of 45 cm.
Eucalyptus comprises about 800 species, endemic to Australia, except for about 10 species in the eastern part of South-East Asia. Many Eucalyptus species are cultivated outside their natural distribution area, in tropical, subtropical and temperate regions, because of their rapid growth and adaptation to a wide range of ecological conditions. In Africa Eucalyptus globulus Labill. has long been the most important Eucalyptus species, but its importance declined, although it is still important in cooler climates. Nowadays the main commercial species in Africa are Eucalyptus grandis W.Hill ex Maiden in more fertile locations, Eucalyptus camaldulensis Dehnh. in drier regions, and Eucalyptus robusta Sm. in tropical regions.
Eucalyptus is divided into several subgenera (7–10, depending on the author), which are subdivided into many sections and series. The results of phylogenetic studies within Eucalyptus suggest that the genus is polyphyletic, hence not of a single evolutionary origin, and consequently it has been proposed to divide the genus into several distinct genera. This has not yet been done, mainly because of the nomenclatural whirlpool this would bring about. Eucalyptus species hybridize easily, which adds to the taxonomic complexity.
Eucalyptus tereticornis is closely related to Eucalyptus camaldulensis and natural hybrids are sometimes encountered. Eucalyptus camaldulensis differs by its usually smaller habit, its beaked to obtusely conical operculum and smooth seeds.
Ecology
Eucalyptus tereticornis occurs from 6–38°S latitude, and climatic conditions in its natural range vary greatly. Rainfall distribution varies from monsoonal with marked dry and wet seasons in southern Papua New Guinea, a summer rainfall climate with a very dry winter in Queensland, and an even distribution of rainfall in southern Queensland, to a dry summer and cold, wet winter in eastern Victoria. It is successfully planted in areas with a mean annual temperature of 14–27°C, a mean maximum temperature of the warmest month of 22–42°C, a mean minimum temperature of the coldest month of 0–19°C and a mean annual rainfall of 400–2300(–3500) mm, with a dry season of up to 8 months. In the drier parts of this range it is grown in temporary flooded locations or with irrigation. In southern China and Pakistan adapted selections are reported to survive temperatures as low as –7°C, but the commonly planted tropical provenances are frost-sensitive. Under natural conditions Eucalyptus tereticornis is mainly found in open forest and as scattered trees on alluvial flats in cooler and drier areas, on lower hill-slopes in higher rainfall areas, and on upper slopes and plateaux in the tropics. Its altitudinal range is from near sea-level up to 1000 m in Australia and up to 1800 m in Papua New Guinea. In East Africa it occurs at 1450–2350 m altitude.
Soil conditions seem to limit its natural occurrence. It is not found on heavy clay and acid soils or on dry, shallow soil, preferring deep, well-drained, fairly light-textured alluvial soil. Eucalyptus tereticornis can stand occasional flooding and in India it is highly resistant to waterlogging during the first year, although in natural forest it is rare under such conditions. It tolerates slightly saline conditions. In many countries it is considered to be more resistant to fire than other Eucalyptus species. Eucalyptus tereticornis proved more drought resistant than Eucalyptus grandis but slightly less than Eucalyptus camaldulensis.
Management
In Ethiopia Eucalyptus tereticornis is planted in parks, woodlots, shelter belts, large-scale plantations and as single trees in farmland. It can be propagated by seed or cuttings. The 1000-seed weight of commercial seed is 1–3 g. About 90% of commercial seed is chaff consisting mainly of unfertilized ovules. For transport of seed, it may be worthwhile to separate seed and chaff, e.g. by sieving. Seed can be stored for several years if air dried and stored in the dark in sealed containers at a temperature of 1–4°C. The germination rate can be maintained at an acceptable level for 1–2 years by storing the seed in unsealed containers at room temperature. The most common and effective way to raise seedlings is to sow the untreated seed in trays under light shade in a sterilized medium (e.g. soil or vermiculite). A sowing rate of 10–15 g/m² is recommended, but the sowing density should be decreased in areas with a high risk of damping off. Seed germinates in 4–14 days. The young seedlings are pricked out and transplanted into containers when 4–8 leaves above the cotyledons have developed. An additional 3–6 months in the nursery is required to obtain seedlings of plantable size. Direct sowing in containers is also practised, but it is very difficult to sow only a few of the minute seeds per container. At planting out in the field, spacings are (1–)3–5 m × (1–)3–5 m. Wildlings may also be used for planting. Vegetative propagation using branch cuttings of 2–3-year-old saplings and suckers has been successful. Methods of in-vitro propagation have been developed.
Clean weeding is extremely important for good establishment and early canopy closure. For the production of fuelwood and pulpwood, rotations of 7–12 years are applied. Thinning is done 2–5 years after planting. Eucalyptus tereticornis coppices vigorously and regeneration by coppice is commonly practised. After the original seedling crop, 2–4 coppice crops can be harvested. About 18 months after cutting, the coppice shoots are thinned to 1–3 per stool. For the production of sawn wood the rotation is 20–30 years with a final density of 70–120 trees/ha.
Eucalyptus tereticornis is fairly free from diseases and pests. Damping-off in the nursery may be a serious problem, but reducing shade and humidity can prevent major damage. Resistance to termite attack is relatively high compared to other Eucalyptus spp., but Neotermes insularis may attack the tree in its natural distribution area.
Near Niamey (Niger) a mean annual volume increment of about 2 m³/ha was recorded, and in northern Côte d’Ivoire a mean annual increment of 10 m³/ha is common. On the best sites in DR Congo annual volume increments of 18–25 m³/ha are obtained, in rotations of 5–7 years. In Congo a mean annual increment of 30–35 m³/ha for the hybrid of Eucalyptus tereticornis and Eucalyptus grandis was recorded over 6–7 years on sandy soil with fertilization.
Genetic resources and breeding
Early introductions of Eucalyptus tereticornis were often derived from only very few original seed trees. The inbred landrace ‘12ABL’ is thought to be descended from a single tree in Madagascar and is widely planted in West Africa; ‘Eucalyptus C’ is a landrace or possibly a hybrid from Zanzibar and is planted in East Africa. ‘Mysore gum’, which represents about half of the eucalypt plantations in India, is believed to originate from a few trees in the Nandi Hills (Andhra Pradesh, India). Provenances have been conserved ex situ in Côte d’Ivoire, Nigeria, Congo, Zambia, Fiji and Bangladesh. Seed is commercially available in Australia from a great number of provenances.
An important effort has been put into progeny and provenance research particularly in the tropical provenances from north-eastern Queensland. Natural populations with intermediate characteristics between Eucalyptus tereticornis and Eucalyptus camaldulensis occur in north-eastern Queensland. These two species also hybridize spontaneously in plantations and artificial crossing in India showed a striking degree of hybrid vigour; the hybrid produced three times the wood volume of Eucalyptus tereticornis at 4 years of age. In Congo Eucalyptus tereticornis × Eucalyptus saligna Sm. showed hybrid vigour. Eucalyptus tereticornis × Eucalyptus grandis showed hybrid vigour in Zambia, but not in South Africa; the hybrid is resistant to pink disease (Corticium salmonicolor) whereas Eucalyptus grandis is not.
Transgenic plants have been produced using Agrobacterium-mediated genetic transformation.
Prospects
Its rapid growth, its adaptability to a wide range of environmental conditions and its wood quality make Eucalyptus tereticornis a promising species for planting in tropical Africa. In village woodlots in Zambia, for instance, it has replaced Eucalyptus grandis, which is less drought resistant and more susceptible to termite attacks. Compared to Eucalyptus camaldulensis, however, it grows slower, gives lower yields and is more sensitive to drought. Testing and selection of locally adapted provenances should receive high priority if Eucalyptus tereticornis is to be utilized to its full potential.
Major references
• Boer, E., 1997. Eucalyptus tereticornis J.E. Smith. In: Faridah Hanum, I. & van der Maesen, L.J.G. (Editors). Plant Resources of South-East Asia No 11. Auxiliary plants. Backhuys Publishers, Leiden, Netherlands. pp. 137–140.
• 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.
• Eldridge, K., Davidson, J., Harwood, C. & van Wijk, G., 1993. Eucalypt domestication and breeding. Clarendon Press, Oxford, United Kingdom. xix + 288 pp.
• Sallenave, P., 1964. Propriétés physiques et mécaniques des bois tropicaux. Premier supplément. Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 79 pp.
• Sallenave, P., 1971. Propriétés physiques et mecaniques des bois tropicaux. Deuxième supplément. Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 128 pp.
Other references
• Chalchat, J.-C, Garry, R.-P, Sidibé, L. & Harama, M., 2000. Aromatic plants of Mali (V): chemical composition of essential oils of four eucalyptus species implanted in Mali: Eucalyptus camaldulensis, E. citriodora, E. torelliana and E. tereticornis. Journal of Essential Oil Research 12(6): 695–701.
• Chilufya, H. & Tengnäs, B., 1996. Agroforestry extension manual for northern Zambia. Regional Soil Conservation Unit, Nairobi, Kenya. 120 + 124 pp.
• Cimanga, K., Kambu, K., Tona, L., Aspers, S., De Bruyne, T., Hermans, N., Totté, J., Pieters, L. & Vlietinck, A.J., 2002. Correlation between chemical composition and antibacterial activity of essential oils of some aromatic medicinal plants growing in the Democratic Republic of Congo. Journal of Ethnopharmacology 79: 213–220.
• Guéneau, P., 1963. Note technique sur quelques propriétés physiques des bois. Centre Technique Forestier Tropical, Nogent-sur-Marne, France. 23 pp.
• Gurib-Fakim, A., Guého, J. & Bissoondoyal, M.D., 1996. Plantes médicinales de Maurice, tome 2. Editions de l’Océan Indien, Rose-Hill, Mauritius. 532 pp.
• Khristova, P., Gabir, S., Bentcheva, S. & Dafalla, S., 1997. Soda-anthraquinone pulping of three Sudanese hardwoods. Tropical Science 37(3): 176–182.
• Khristova, P., Kordsachia, O., Patt, R. & Dafaalla, S., 2006. Alkaline pulping of some eucalypts from Sudan. Bioresource Technology 97(4): 535–544.
• Lamb, D., Johns, R.J., Keating, W.G., Ilic, J. & Jongkind, C.C.H., 1993. Eucalyptus L’Hér. In: Soerianegara, I. & Lemmens, R.H.M.J. (Editors). Plant Resources of South-East Asia No 5(1). Timber trees: Major commercial timbers. Pudoc Scientific Publishers, Wageningen, Netherlands. pp. 200–211.
• Parant, B., Chichignoud, M. & Curie, P., undated. Présentation graphique des caractères technologiques des principaux bois tropicaux. Tome 8. Bois du Burundi. CTFT, Nogent-sur-Marne, France. 82 pp.
• Silva, J., Abebe, W., Sousa, S.M., Duarte, V.G., Machado, M.I. & Matos, F.J., 2003. Analgesic and anti-inflammatory effects of essential oils of Eucalyptus. Journal of Ethnopharmacology 89(2–3): 277–283.
Sources of illustration
• Boer, E., 1997. Eucalyptus tereticornis J.E. Smith. In: Faridah Hanum, I. & van der Maesen, L.J.G. (Editors). Plant Resources of South-East Asia No 11. Auxiliary plants. Backhuys Publishers, Leiden, Netherlands. pp. 137–140.
Author(s)
M. Brink
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
Based on PROSEA 11: ‘Auxiliary plants’.

Editors
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
M. Brink
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
General editors
R.H.M.J. Lemmens
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
L.P.A. Oyen
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
J.R. Cobbinah
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:
Brink, M., 2008. Eucalyptus tereticornis Sm. In: Louppe, D., Oteng-Amoako, A.A. & Brink, M. (Editors). Prota 7(1): Timbers/Bois d’œuvre 1. [CD-Rom]. PROTA, Wageningen, Netherlands.
1, tree habit; 2, flowering twig; 3, leaf of young plant; 4, leaf of adult plant; 5, flower buds; 6, fruits.
Source: PROSEA



5-year-old plantation, Côte d'Ivoire


wood in transverse section


wood in tangential section


transverse surface of wood