Maheshwar Hegde1, K. Palanisamy1 and Jae Seon Yi2.
Acacia mangium Willd. -
A Fast Growing Tree for Tropical Plantation
1Institute of Forest Genetics and Tree Breeding, R. S Puram, PB 1061 Coimbatore -641002, India
2College of Forest and Environmental Sciences, Kangwon National University, Chuncheon 200-701, Republic of Korea
Taxonomy
Acacia mangium Willd. belongs to Acacia genus, which was originally described as Mangium montanum Rumph in Herbarium Amboinense 3:123, t.81 (1750) but transferred to Acacia by C.L. Willdenow in Sp. Plant 4: 1053 (1806). The specific name is an allusion to Rumphius’ observation that this tree resembled ‘mangge’ or mangroves in Indonesia. Acacia contains 1,200-1,300 species and is divided into three subgenus: Acacia, Aculeiferum and Phyllodinae (Maslin 1995). A. mangium is in Phyllodinae subgenus classed into seven sections, containing more than 900 species (Maslin and McDonald 1996). A. mangium is assigned to section Juliflorae (235 species), a group characterized by having flowers in elongated spikes and numerous phyllodes, often anatomizing by longitudinal nerves. A. mangium may easily be confused with A. holosericea and A. neurocarpa, but it can be readily distinguished by its arborescent habit, glabrous phyllodes and branchlets, white to cream flower spikes and seed with an orange aril (Maslin and McDonald 1996), while other two occur naturally as shrubs or small trees on drier sites.
Distribution
A. mangium has a fragmented natural distribution which stretches from Indonesia (i. e. on the islands of Sula, Ceram, Aru, and Iriyan Jaya), Papua New Guinea (PNG) and north-eastern Queensland in Australia (Fig. 1). The range is 1º-18º-57'S latitudinal and 125°22'-146°17'E longitudinal. The mean altitudinal range is from just above sea level to about 100 m, with an upper limit of 780 m. In Asia, the country with A. mangium natural population distribution is Indonesia. In Oceania, there were Australian Northern Territory, Queensland and Papua New Guinea. A detailed description of the natural distribution and ecology about A. mangium is available in Awang and Taylor (1993) and Krisnawati et al. (2011).
Fig. 1. Generalized range of natural distribution of Acacia mangium.
A. mangium was introduced into many countries. For example, Indonesia and Malaysia have established large-scale plantations for the production of paper pulp. In China, the Philippines, Thailand and Vietnam, the commercial planting of A. mangium is increasing very quickly (Awang and Taylor 1993). Of course, the species has also been introduced to other countries as a plantation tree, such as other Asia countries (Bangladesh, China, Taiwan, India, Indonesia, Laos, Malaysia, the Philippines, Sri Lanka, Thailand, and Vietnam), Africa (Benin, Congo, Cote d’Ivoire, Democratic Republic of Congo, Kenya, Madagascar and Zimbabwe) and Western Hemisphere (Brazil, Costa Rica, Cuba and Hawaii).
Environmental Conditions
Soil
A. mangium is typically a low elevation species chiefly associated with rainforest margins and disturbed sites on well-drained acid soils (pH 4.5-6.5) of low fertility. It also occurs behind mangroves, in seasonal swamps, along streams, and on well-drained flats, low ridges and mountain foot hills (Pinyopusarerk et al. 1993).
Climate
A. mangium distribution area is including the tropical warm and hot climate, either humid or wet zones characterized by a short winter dry season and high total annual rainfall. The mean maximum of the hottest month is about 30-34°C and the mean minimum of the coolest about 15-22°C. It is unsuitable in the area where the absolute minimum temperature falls below 0°C (Yan et al. 1996), so its distribution area is frost-free. In a typical location, the 50% rainfall is 2,150 mm; the 10% is 1,300 mm; and the lowest, on record, is 1,000 mm. It prefers wet sites with an annual rainfall of 1,000-4,500 mm. Prolonged dry periods will slow down the tree growth (Mergen et al. 1983). While the annual rainfall of over 2,500 mm in the Bengkoka/ Kudat region of Sabah is considered adequate for growth. Moreover, it is still affected by seasonal conditions (Pinyopusarerk et al. 1993). During the dry season, when monthly rainfall is below 100 mm and the evaporation rate exceeds 130 mm per month, the tree is under drought stress.
Vegetation types
A. mangium grows on the margins of closed forest (rain forest), in open forest and woodland, especially where there is disturbance by fire. In northern Queensland it occurs in tall forests on well-drained sites of the foothills and lowlands associated with various eucalypts and acacias. As a component of fringing vegetation on river banks, it is frequently associated with rain forest species such as Flindersia brayleyana and Cardwellia sublimis. Elsewhere, it occurs on the slightly better-drained sites within the swampy coastal plains where Melaleuca are locally dominant. Tracey (1982) described the vegetation types in humid, tropical Queensland.
In Papua New Guinea, It occurs in tall woodland and open forest, frequently in mixed associations with other Acacia, Melaleuca and Lophostemon spp. These vegetation types are described by Paijmans et al. (1971), Paijmans (1976) and Skelton (1987). At the western extremity of its range in Indonesia, A. mangium is dominant in small stands on disturbed sites in or on the fringes, closed-forest and Melaleuca spp. woodland.
Botanical Descriptions
Tree morphology
A. mangium is a kind of evergreen tree, up to 30 m tall. The general feature is presented in Fig. 2. The bole can be unbranched for more than half of the total tree height. It is sometimes fluted at the base and the tree diameter rarely exceeds 50 cm. Bark is rough and furrowed, either grey or brown in color. Small branches are winged. It may be reduced to a small tree or large shrub of 7-10 m on unfavorable sites. The bark surface is rough, furrowed longitudinally, and varies in colour from pale grey-brown to brown. The lower bole is sometimes fluted. Detailed botanical description refers to Pedley (1975).
Fig. 2. Feature of Acacia mangium. 1-Habit of young tree; 2-flowering twig; and 3-pods (Source: DFSC seed leaflet).
Leaves (phyllodes)
Borne on very acutely angled, glabrous and stout branchlets, the mature phyllodes of A. mangium are very large, normally 11-27 cm long and 3-10 cm broad. They are dark green, glabrous on a glabrous pulvinus 0.6-1 cm long. The phyllodes are characterized by four (rarely three or five) main longitudinal nerves, basally confluent but distinct from lower margin, minor nerves strongly anatomizing to form a prominent reticulum (Maslin and McDonald 1996). A gland (extra floral nectary) is conspicuous at the base of the phyllode (Fig. 3).