Agroforestree Database

Local names:
 English (sabah salwood,mangium,hickory wattle,brown salwood,black wattle), Filipino (maber), Indonesian (tongke hutan,nak,mangge hutan), Malay (mangium), Polynesia (arr), Spanish (zamorano), Thai (krathin-thepha,kra thin tepa), Trade name (brown salwood)

Acacia mangium is a single-stemmed evergreen tree or shrub that grows to 25-35 m in height. Young trees have smooth, greenish bark; fissures begin to develop at 2-3 years. Bark in older trees is rough, hard, fissured near the base, greyish-brown to dark brown, inner bark pale brown. Bole in older trees branchless for up to 15 m, fluted, up to 90 cm in diameter; branchlets acutely triangular.

Phyllodes are large up to 25 cm long and 3.5-10 cm broad, 2-5 times as long as wide, straight or straight along 1 side and curved along the other, with 4 (max. 5) main longitudinal veins, secondary veins finely anastomosing; glaborous, pulvinus 6-10 cm long. A gland (extra floral nectary) is conspicuous at the base of the phyllode.

Inflorescence is composed of many tiny white or cream flowers in spikes. Flowers are quinqeufloral; the calyx is 0.6-0.8 mm long, with obtuse lobes; corolla 1.2-1.5 mm long. Peduncles are canescent and pubescent, about 1 cm long; rachis is also canescent and pubescent.

Pods are broad, linear and irregularly coiled when ripe. They are membranous or slightly woody, inconspicuously veined. 3-5 mm wide and 7-10 cm long. Ripening pods change from green to brown, stiff and dry. Seeds are black and shiny with shape ranging from longitudinal, elliptical, ovate to oblong, 3-5 mm by 2-3 mm. The seeds are arranged longitudinally and attached to the pods by an orange to red folded funicle.

The generic name acacia comes from the Greek word ‘akis’, meaning a point or a barb.
This acacia was originally described as Mangium montanum Rumph.  in Herbarium Amboinense (1750) but changed to an Acacia in 1806. The specific name is an allusion that this tree resembled 'mangge' (mangroves in Indonesia).

Ecology

A. mangium is a species of the humid, tropical lowland zones. It tolerates pH levels between 4.5 and 6.5. It occurs behind mangroves in seasonal swamps, along streams and on well-drained flats, low ridges and mountain foothills. A. mangium occurs in the Aru Islands, Irian Jaya, Seram, the Sula Islands of Indonesia; Western Province of Papua New Guinea; and northeastern Queensland, Australia. It is sometimes found dominant in primary and secondary forest, forest margin, savannah, grassland, savanna woodland, on poorly drained floodplains and along fringes of mangrove forest, where it is sometimes associated with Melaleuca and Rhizophora species. In Papua New Guinea, it often prefers slightly higher and drier sites than other Acacia species growing in the same area. This species has been successfully planted on abandoned areas of shifting cultivation colonized by Imperata cylindrica grass, but does not tolerate waterlogging and soils derived from ultrabasic rocks.

Native range
Australia, Indonesia, Papua New Guinea

Tree management

A. mangium grows fast; it can achieve a mean annual diameter increment of up to 5 cm and a height of up to 5 m in the 1st 4-5 years. It is reported to grow 3 m tall in the 1st year in Sabah and Sumatra, and in the Philippines it reached an average height of 8.3 m and diameter 9.4 cm after a further 2 years. However growth declines rapidly after 7 or 8 years. Except under ideal conditions or over periods of more than 20 years, the tree will probably not exceed 35 cm in diameter and 35 m in height. In Sabah, 14-year-old trees were 30 m tall and 40 cm in diameter. Provenances from Papua New Guinea consistently show better growth in height and diameter and superior form.

Optimal growth of trees is achieved most effectively if vesicular arbuscular mycorrhizal fungi such as Glomus fasciculatus and Gigaspora margarita are present in combination with Rhizobium. Technologies for the commercial production of rhizobial and VAM innoculants are now available in Southeast Asia. The ectomycorhizal fungus Thelephora ramaroides has been identified in association with A. mangium.

Acacia species are pioneers that demand full light for good development; in shade, A. mangium growth is stunted and spindly. Trees are renowned for their robustness and adaptability, which makes them good plantation species. Survival after planting out A. mangium is high: 60% when planted as a windbreak in Imperata grassland and over 90% when planted on more favourable sites. Plantation canopy cover occurs after 9 months to 3 years, depending on soil fertility, weediness and initial spacing. In Sabah in a plantation with an initial spacing of 3 x 3 m, the canopy closed in 1 year. In the 1st year, the plantation should be protected from livestock, as they browse the trees, and it should be weeded, taking particular care to remove climbers, creepers and vines. A. mangium has been found very sensitive to herbicides.

As trees have a tendency to produce multiple leaders from the base, singling is carried out at 4-6 months after planting. Persistem branches are pruned out only in plantations where the objective is to produce quality saw or veneer logs. Usually pruning is done twice; the 2nd time the branches are pruned out farther up the trunk, often to a height of 6 m. Pruning out branches with diameter of 2 cm or more makes the tree susceptible to infections, especially heart rot. Trees are very responsive to extra growing space. The thinning carried out in plantations for pulpwood production is aimed at achieving a final stock of 600-700 stems/ha from the 1 250 trees/ha planted. It is executed after 18 months. These plantations are clear felled after 6-8 years. In plantations producing quality logs, the initial number of trees is generally thinned, reducing them from 900 ha to 100-200/ha in 2 or 3 thinnings. The 1st thinning is done when trees are 9 m tall, that is, before 2 years of age. The rotation is 15-20 years. In Papua New Guinea, plantations grown on a 7-8 year rotation for pulpwood are not thinned. Trees are felled for pulpwood 6-7 years after planting; for sawn timber the rotation is 15-20 years.

The productivity of trees has been found to be closely related to ‘total’ soil potassium levels in Kalimantan (accounting for 50% of the variation in data) and phosphorus levels in Malaysia.

For the production of seedlings, the pods should be processed as soon as possible after harvesting. Pods and seeds should not be left long to dry in the sun, as temperatures exceeding 43 deg. C reduce viability. Seed storage behaviour is orthodox. There is little loss in viability (6%) after 1-2 years storage at 4-5 deg. C. There are about 66 000-120 000 seed/kg.

A. mangium is a species of the humid, tropical lowland zones. It tolerates pH levels between 4.5 and 6.5. It occurs behind mangroves in seasonal swamps, along streams and on well-drained flats, low ridges and mountain foothills. A. mangium occurs in the Aru Islands, Irian Jaya, Seram, the Sula Islands of Indonesia; Western Province of Papua New Guinea; and northeastern Queensland, Australia. It is sometimes found dominant in primary and secondary forest, forest margin, savannah, grassland, savanna woodland, on poorly drained floodplains and along fringes of mangrove forest, where it is sometimes associated with Melaleuca and Rhizophora species. In Papua New Guinea, it often prefers slightly higher and drier sites than other Acacia species growing in the same area. This species has been successfully planted on abandoned areas of shifting cultivation colonized by Imperata cylindrica grass, but does not tolerate waterlogging and soils derived from ultrabasic rocks.

A. mangium can be propagated from seed (direct sowing or in the nursery) and by air-layering, cuttings, grafting and tissue culture. Propagation by seedling is best although direct sowing is also possible. Regeneration through coppicing or pollarding is poor. Seeds are pretreated before sowing by immersing them in boiling water (100 deg. C) for 30 seconds then soaking them in cold water for 24 hours; alternatively, they may be manually scarified. The germination rate is high, generally 75-90%, and germination is rapid, occurring within 1 month. Seeds may be sown in seedbeds and pricked out 6-10 days after sowing; recovery rate with this method is about 37%. Sowing in germination trays (wet towel method) and pricking out the seedlings 6-10 days after sowing when the radicle emerges gives 85% recovery. Another option is direct sowing in containers (polythene bags, open-ended hanging pots called ‘root trainers’ or other permanent pots) followed by pricking out to maintain 1 seedling per container. There are no specific requirements for the type of substrate; mixtures of topsoil, peat, old sawdust, rice husks, sand and vermiculite are used. Even a pure mixture of peat vermiculite with a pH of 3.1 presented no problems. A mixture of peat (70-80%) and rice husks (30-20%) has been used successfully in Sumatra. Nitrogen-phosphorus potassium fertilizers are generally applied in the nursery, but fertilization is stopped when ‘hardening off’ the plants by reducing watering and exposing them to full sunlight. The appropriate height for transplanting is 25-40 cm, when the seedlings have been in the nursery for 9-16 weeks. Plants can also be propagated vegetatively through single-node stem cuttings 4-5 cm long and 0.5-1.5 cm in diameter, leaving 0.5-1 phyllodes. The application of indole-butyric acid or rooting powder enables 65-75% rooting; rooting is reported to be slow. Air-layering gives promising results. Trees regenerate abundantly in clear-felled areas or where a light fire has occurred. However there is no report of a crop grown from natural regeneration.

Erosion control:  A. mangium is employed in soil conservation.

  The germinating seeds can be cooked and eaten as a vegetable.

Young shoots and leaves are browsed by buffalo and cattle. Studies indicate they are high in crude protein content but with low in vitro dry matter digestibility.

With a calorific value of 4 800-4 900 kcal/kg, A. mangium provides good quality charcoal and is suitable for the manufacture of charcoal briquettes and artificial carbon.

Fibre:  The pulp is readily bleached to high brightness levels and is excellent for papermaking. The neutral sulphite semi-chemical pulping of A. mangium gives yields of 61-75%. It is currently grown primarily for pulp and paper in Sabah, Sumatra and Vietnam. Wood also makes excellent particleboard.

Timber:  A. mangium is an important source of wattle timber; the wood is used for construction, boat building, furniture and cabinet making, and veneer. It makes attractive furniture and cabinets, mouldings, and door and window components. Conversion into veneer and plywood is feasible with no specific processing requirements. It is unsuitable for timber because it contains knots and flutes, has a high incidence of rot and is subject to termite attack. Its density is (min. 450) 530-690 kg/cubic m at 15% mc.

Shade or shelter:  With its dense foliage, retained throughout the year, A. mangium makes a useful shade tree, screening and soil cover crop. It has been used experimentally in Sabah to shade cocoa. It can also be planted as a wind or firebreak.

Tannin or dyestuff:  It has high tannin content (18-39%), justifying commercial exploitation of tannins.

Nitrogen fixing:  A. mangium trees form a symbiosis with soil bacteria of the genus Rhizobium, leading to root nodules, in which the bacteria transform free nitrogen into organic and inorganic compounds containing nitrogen.

Ornamental:  In Malaysia, A. mangium is a widely planted roadside tree, and in Thailand, it is recommended for wider use in urban forestry.

Intercropping:  Experiments have shown that it has potential in some intercropping combinations, such as with maize or peanuts.