Acacia mangium (brown salwood)
Acacia mangium at Habit Mission Beach, QLD (Photo: Maurice Mcdonald)
brown salwood (Australian standard trade name), mangium, Sabah salwood, black wattle, hickory wattle (Australia); tongke hutan, manggee hutan (Indonesia); biar (Papua New Guinea)
Not listed on the IUCN Red List of Threatened Species. Widely distributed and reproduces easily. Not considered to be threatened.
In Australia it grows in coastal tropical lowlands on the margins of rainforest, where it occurs in the foothills of coastal ranges over metamorphic, granite and acid volcanic formations, and also on sandy or loamy alluvium of the coastal plain.
Dust from pods pounded during seed extraction causes a respiratory reaction in some people.
About this species
Acacia mangium is a major plantation species in the humid tropical lowlands of Asia. Its success is due to its extremely vigorous growth rate, tolerance of highly acidic, low nutrient soils, ability to grow reasonably well where competition is severe (for example Imperata grasslands), relative freedom from disease, wood properties that make it suitable for a wide range of uses, and ease of establishment in cultivation. Plantations in Indonesia and Malaysia are the resource base for a large pulp and paper industry. Other uses included fuelwood, timber for building and furniture and particle board.
Acacia section Juliflorae is a group of about 250 species, mostly confined to Australia. Acacia mangium is one of a relatively small tropical sub-group of these species, which in recent years have been developed as plants of major economic importance. Other important species in this group are A. auriculiformis, A. auriculiformis x mangium and A. crassicarpa.
Geography and distribution
Acacia mangium has a disjunct and relatively restricted natural distribution that extends from far north-east Queensland, Australia, through the Western Province of Papua New Guinea to the Indonesian provinces of Irian Jaya and Maluku. It has been introduced into many countries, most notably in Asia (China, Indonesia, Lao PDR, Malaysia, Myanmar, Thailand, the Philippines and Vietnam), but also Bangladesh, Brazil, Cameroon, Costa Rica, Hawaii and Nepal.
The natural distribution of Acacia mangium overlaps the warm and hot tropical climatic zones. In these areas the temperatures are high and equable throughout the year, with the mean maximum hottest month at 31-34°C and the mean minimum coolest month at 15-22°C. The mean annual rainfall is 1,500 to 3,000 mm, with summer (January to March) being the wettest period. Brown salwood grows best in well-drained, acidic soils (pH of less than 4.0) of moderate to low fertility. It grows well in areas of disturbance and has the potential to become weedy under certain conditions.
Brown salwood is normally a large tree, which grows up to 30 m tall, with a straight trunk that can occupy over half the total tree height, and which is sometimes fluted at the base. On adverse sites it may grow as a small tree or large shrub of 7–10 m tall. The pale grey-brown to dark brown bark is rough and longitudinally furrowed. The branchlets are acutely angled and hairless.
The phyllodes (leaf-like petioles) are obliquely narrowly elliptic to elliptic, large (normally 11–27 cm long and 3-10 cm wide), with three or four main longitudinal nerves which merge at their base. The minor nerves strongly cross-connect to form a fine, elongated network between the main nerves.
The white to cream flowers are pentamerous (have parts arranged in groups of five) and are loosely aggregated into spikes, which are 5 to 12 cm long. The pods are openly coiled and twisted, or sometimes tightly spirally coiled, 3 to 5.5 mm wide, leathery to sub-woody, and hairless. The black seeds are 3.5–5 x 2–3 mm, and have a small, bright, yellow or orange aril (fleshy growth) at their base.
Threats and conservation
Acacia mangium is a pioneer species which regenerates easily from seed, and is not considered to be threatened. It can become weedy outside its natural range, and this issue requires attention in areas where it is being cultivated.
Acacia mangium is one of a group of tropical Australian species that are now extensively used in commercial plantations in Southeast Asia (and also in Brazil), where they form the basis of substantial plantation-based industries. In 2006 the Asian plantations exceeded 1.5 Mha and had been established in China, Malaysia, Indonesia, Papua New Guinea, the Philippines, Thailand, Vietnam and Melville Island in Australia. Acacia mangium grows fast: saplings can grow up to 5 m tall within 5 years, with increases in diameter of up to 5 cm per year.
Brown salwood is highly versatile and is used both on an industrial and local operator scale. The majority of large-scale plantations are used for the production of paper pulp, kraft pulp (for bags, wrapping paper, linerboard) and chemical pulp (for corrugating, medium and higher-grade products). In Indonesia alone it is estimated that over four million tonnes of Acacia pulp will be produced for the international market in 2010. Based on the current price of 550 US dollars per tonne this represents a commodity worth 2.2 billion US dollars.
The growth form of Acacia mangium renders the species suitable for a wide range of solid wood products including furniture- and cabinet- making, light structural works, agricultural tools, boxes and crates. It has even been used for house construction in Australia. Much of the furniture marketed today as ‘Acacia Wood’ is derived from plantation-grown Acacia mangium, particularly from Indonesia. Other industrial products manufactured from this species include wood pellets, activated carbon and charcoal. The dense wood of mature plants is a source of good fuel, but young trees make poor firewood.
In international trade the names 'Acacia Wood' or simply 'Acacia' are used to brand furniture and other wood products made primarily from plantation-grown Australian Acacia species such as Acacia mangium and some close relatives. The image below shows the Forestry Stewardship Council (FSC) branding of Acacia wood furniture manufactured in Vietnam and destined for the European, North American and Australian markets. (FSC is an independent, non-governmental organisation devoted to promoting responsible management of the world's forests).
Millennium Seed Bank: Seed information
Description of seeds: Average 1,000 seed weight = 14.6 g.
Seed storage behaviour: Orthodox (the seeds of this plant survive being dried without significantly reducing their viability, and are therefore amenable to long-term frozen storage such as at the MSB)
Composition values: Oil content 11.9%
Brown salwood is a fast-growing, relatively short-lived (30 to 50 years) species adapted to a wide range of acidic soils in moist tropical lowlands. It can fix nitrogen after forming nodules containing soil bacteria (Rhizobium and Bradyrhizobium spp.) in many tropical soils, but its nitrogen-fixing potential may only be realised in many soils if adequate fertiliser is applied. It is frost-sensitive and is killed by fire only if the stem diameter is less than about 10 cm.
Mature seed requires pre-germination treatment such as mechanical scarification (scratching the surface) or boiling water to break dormancy. After suitable treatment germination is rapid and typically exceeds 75%. Flowering and seeding commence at about two to three years of age under plantation conditions. Research into vegetative propagation is continuing and progress to-date is encouraging. Plantations are generally established using containerised seedlings. Direct seeding has been tried but the results are variable. Acacia mangium stumps coppice profusely, but the coppice shoots lack vigour and are unsuitable for the second rotation. Plant spacing is governed by the need for rapid canopy closure and the end-products required. Therefore, practice varies, for example 900 stems per hectare are planted in Peninsular Malaysia and up to 1,680 stems per hectare in Sabah. In Sabah, under optimal conditions, A. mangium attains 20-25 m and 20-30 cm stem diameter in 10 to 13 years. In this same area, un-thinned stands planted at 1,075 to 1,680 stems per hectare attain maximum MIA (mean annual increment) after six years on quality sites and seven years on poorer sites.
A. mangium prefers fertile sites with good drainage, but will tolerate low fertility soils with impeded drainage. Soil depth and topographic position can influence yields; volume production on deep alluvium may be almost double that on skeletal soils. There are also significant differences in performance under cultivation with respect to distance from the equator. Growth is generally faster at sites near the equator, with a mean annual height increment of about 3 to 4 m. Slower growth occurs on sites further from the equator.
Brown salwood at Kew
There is a specimen of Acacia mangium in the Economic Botany Collection, one of the behind-the-scenes areas of Kew. The details of this specimen can be viewed using ePIC (the electronic Plant Information Centre).
Dried specimens of Acacia mangium are also held in Kew’s Herbarium, where they are made available to bona fide researchers by appointment. The details of specimens collected in the Philippines in 1992 can be viewed in the Herbarium Catalogue.
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Midgley, S.J., Turnbull, J.W. & Pinyopusarerk, K. (2003). Industrial Acacias in Asia: small brother or big competitor? In: R-P. Wei & D. Xu (eds). Eucalyptus Plantations – Research, Management and Development (Conference held in Guangzhou/Zhaoqing, China), pp. 19-36. (Publ. World Scientific: Singapore).
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Kew Science Editor: Bruce Maslin (Australian Botanical Liaison Officer 1977-1978)
Kew contributors: Olwen Grace (Sustainable Uses Group)
Copy editing: Emma Tredwell
Kew would like to thank the following contributors: Stephen Midgley
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