Production and Management

Establishment

Mangium is a robust plant, producing a vigorous root system and surviving many adversities. Its seed germinates well in the nursery provided it is properly pretreated, and the seedlings are relatively easily established in the field.

The trees can be planted using nursery-raised seedlings-either containerized or bare rooted. Also, plantations can probably be established by direct seeding, or mangium can be vegetatively propagated by airlayering, cuttings, or grafted stock. Natural regeneration takes place readily, but disturbance of the understory, as by fire, is usually necessary for large- scale natural regeneration. Stumps of young trees coppice.

Fruiting is prolific. Individual trees in a 14-year-old mangium plantation in Sabah produce as much as 1 kg of seed per year; the average is 0.4 kg.

Seed pods are collected when they turn brown at the end of the dry season. They are dried in the sun (or in warm air) for 24-48 hours and are then broken either by 10 minutes of tumbling in a cement mixer with heavy wooden blocks or by beating in a commercial thresher. (Both processes may produce irritating dust, and operators should wear a respirator.) The seeds are then sieved clean of pod debris and winnowed by hand or machine to remove chaff. The bright-orange funicles remain attached to most seed. There are 80,000-110,000 seeds per kg, and each kg of ripe pods yields about 90 g of seeds.

Storing the seed presents no problem. Once dried (to 6-8 percent moisture content) and placed in an airtight container, the seed maintains a germinability of 75-80 percent for several years.

Seed Treatment

Seeds of mangium, like those of most acacias, germinate poorly unless the impervious seed coat is pierced so that the endosperm and embryo can take up water. This is normally achieved by boiling some water, removing it from the heat source, and immediately pouring in the seed. After 30 seconds the hot water is poured off and replaced by tap water (25°C). The seed is then allowed to soak overnight. The volumes are important: 1 part seed to 10 parts boiling water is best, and the 30-second treatment time should be carefully observed. The pretreated seed can be dried and stored for later use, at which time no further treatment is required.

Sabah foresters broadcast the treated seeds on prepared nursery beds and cover them lightly with fine sand or soil. Germination starts within 2-3 days and is complete in 8-10 days. When the first pair of leaflets shows, the seedlings are transplanted into perforated plastic bags (16-20 cm X 5-7 cm). (Seed lots of high germinability can be sown directly in the plastic bags.)

Seedlings are transplanted to the field when they reach 25-30 cm in height (2-3 months). By this time, prolific nodulation occurs, and the seedlings' roots have picked up mycorrhizae. No inoculation with rhizobia or mycorrhizae is needed, at least in Sabah and Bangladesh.

Plantation Management

Planting is done during the rainy season. Although the site is usually burnt to remove grass competition, and large trees and shrubs are felled, little further site preparation is needed. In some Imperata areas, trampling around the planting hole is the only preparation. Optimum spacing has not yet been determined, but 3 m x 3 m is commonly used. The rapid shading of the ground is important for suppressing vigorous tropical weeds. In heavy stands of Imperata grass an area surrounding each seedling is often cleared with a machete at 1.5, 3, and 5 months, and weeds between the rows are also slashed at the third month. (Mangium trees are particularly susceptible to herbicides.) The stands are then given no more attention, and canopy closure takes place 9 months to 3 years later, depending on the fertility and weediness of the site.

In Sabah, fertilizer practices vary. On most sites the trees so far have shown little response to fertilizer, and usually mangium plantations are not fertilized. However, 100 g of rock phosphate is sometimes applied in the hole at the time of planting, and on extremely poor soils fertilizer is sometimes needed.

Recommendations on thinning and other plantation management practices are not yet available.

Growth Rate

On good sites mangium grows quickly (see Table 1). In Sabah some specimens have reached 23 m in height in 9 years. Average increases in diameter of 2-3 cm per year are common. Untended stands have produced 415 m3 of timber per ha after 9 years, representing an annual yield of 46 m3 per ha.

On poor sites, such as those with soils that are shallow, low in nutrients, badly disturbed, compacted, or seasonally inundated, production is less, but annual yields exceeding 20 m3 per ha have often been achieved. In the oldest plot trials, the trees reached a mean height of 25 m and a mean diameter of 27 cm at age 13 years. The largest tree was 25 m tall and 51 cm in diameter.

In commercial plantations at Sabah Softwoods, mangium grows as high as 3 m in the first year, with an expected annual growth of 5 m in height and 4 cm in diameter in the following 3 years. Average stands of 4-year-old trees are annually producing 27 m3 per ha, with the most productive stands yielding 44 m3 per ha. This growth is comparable to that of Eucalyptus deglupta and other fast-growing species.

In the Philippines mangium has grown well at Pagbilao, Mindanao. In 3 years it reached an average height of 8.3 m with a diameter of 9.4 cm. In trial plantings by a paper company, 2- year-old trees reached an average height of 5.8 m, with an average diameter of 7.1 cm at one site and an average total height of 6.8 m and an average diameter of 7.7 cm at another.

In Bangladesh some plots on good sites average 8 m in height and 15 cm in diameter at 2 years of age. Trials on poor sites, such as gravelly soil over a lateritic hardpan, indicate the growth reached is only half of that but is still better than several provenances of Eucalyptus camaldulensis, E. tereticornis, end E. brassiana.

In Hawaii, trials of trees for energy production show that after 2 years on a poorly drained site mangium averaged 6 m in height and 6.8 cm in diameter and outperformed 10 species of Eucalyptus. On other sites, however, several of the eucalypts proved superior.

TABLE I Mangium Yields in Various Locations in Sabah

		MAI	Mean	Mean
	Age	Volume	Height	Diameter	Spacing
Location	(years)	m3/ha/year	(m)	(cm)	(m)
Brumas(a)	4	44.5	20.7	14.3	2.4 x 2.4
Brumas(b)	4	13.8	18.1	11.5	3 x 3
Gum Gum(c)	13	-	25.0	27.0	2.4 x 2.4
Sibuga(d)	10	43.9	23.0	20.0	2.4 x 2.4
Sook (e)	6	-	17.0	13.4	3 x 3
Jalan Madu (f)	13	-	20.0	30.0	2.4 x 2.4
Jalan Lee (g)	9	-	17.0	21.0	3 x 3

Locations:

(a) Logged-over forest (burned, little soil disturbance; sandy-clay, pH 4-5 (plantation conditions, more than 50 ha).

(b) Logged-over forest (burned with compaction due to logging; plantation conditions, more than 50 ha).

(c) Logged-over forest (burned with compaction due to logging; plantation conditions, more than 50 ha.

(d) Grassland, flat lowland with periodic flooding (trial plot 0.04 ha).

(e) Grasslands-bracken, alluvial soil with surface of compacted fine white sand of various depths (espacement trial, total area 1.42 ha).

(f) Badly eroded heavy cover of Imperata, sandstone shale (firebreak).

(g) Heavy cover of Imperata, alluvial (firebreak). The figure given is an average: the firebreak extended from alluvial wash at the foot of the slope to skeletal rocky soil at the top of a 90 m hill. Actual growth ranged from 20.7 m mean height and 26.5 cm diameter to 11.0 m height and 14.6 cm diameter, demonstrating a sensitivity to site even in this tolerant species. (Information from N. Jones)

In Costa Rica mangium does well on good sites, averaging a height of 8 m and a diameter of 9 cm after 2 years.

Diseases and Pests

Mangium is affected by some diseases and pests, but the problems they cause have not yet been serious. The worst is a heart rot that is white and fibrous and is surrounded by a dark stain. It has been found in 12 percent of the stems cut in one 44-month-old plantation in Sabah, although such extensive decay in such young trees is uncommon elsewhere. Neither the cause of the disease nor its mode of entry is known at this time.

In Sabah, "pink disease" caused by Corticium salmonicolor is occasionally observed attacking the trunk of mangium, resulting in the death of the crowns. So far this disease appears to be of little consequence, since few trees are affected.

In a nursery in Hawaii, mangium seedlings have been heavily attacked by a powdery mildew (Oidium species). Nearby Acacia koa and Acacia melanoxylon seedlings were free of the disease.

Several insects affecting mangium have been reported in Sabah. At least three undetermined species of pinhole borers (of the families Platypodidae and Scolytidae) sometimes attack a high percentage of trees, especially on poor sites. The living tree suffers little, but the insects'galleries could lower the timber quality.

Also in Sabah, carpenter ants (Camponotus species) and subterranean termites (Coptotermes species) have been found forming galleries in the heartwood of young trees, and a Cerambycid wood borer (Xystocera species) has been observed attacking mangium in some localized areas. The carpenter ant may be a potentially serious problem; up to 32 percent of the trees were attacked in one area. An undetermined species of bagworm sometimes causes severe defoliation in Sabah, but trees quickly recover. Mangium seedlings are sometimes also defoliated by Hyphomeces squamosus.

Like many other Acacia species, mangium is susceptible to attack by scale insects and mealy bugs, particularly at the seedling and sapling stages.

Other Plantation Problems

In its first few years of life mangium can be damaged or killed by fire, and where a heavy grass cover is present fire must be excluded. Older trees suffer bole damage from "hot" fires but are only killed if the grass and weed cover is exceptionally thick around the tree base.

Cattle, goats, and other livestock will browse mangium foliage and should be kept away from plantations at least for the first year.

In Sabah it has been noted that some extremely vigorous specimens in mangium plantations have seed pods intermediate in character with those of Acacia auriculiformis. Hybridization between the two species has now been demonstrated. Some hybrids grow with mangium's straight trunk and long bole; others, however, have the poor form of Acacia auriculiformis. Because this hybridization results in progeny of various forms and growth, some of which are of less-desirable quality, it is not advisable to grow mangium and Acacia auriculiformis in proximity.