Acacia mangium

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Mangium is a major fast-growing tree species in forestry plantation programmes in Asia and the Pacific. It tolerates varied site conditions and has adaptability to different planting objectives. Mangium shows most vigorous growth on well-drained, fertile soils in high rainfall areas (>2000 mm annually) in the humid tropics.


Propagation
Flowering in mangium is precocious. It starts to flower and produces seeds 18-20 months after planting. Pods can be collected from the trees in January-February under Kerala conditions, when the pods turn very dark-green to light-brown in colour. Seeds are extracted manually after sun-drying. Pods and seeds should not be left to dry in the sun for long. Store the seeds under dry and insect/rodent-free conditions. The number of seeds in one kg of pure seed varies among trees (mean: 125,000 seeds per kg). 

Pre-sowing treatment and nursery practices

To break dormancy of mangium seeds, hot water treatment is recommended. The seeds are tied in porous cloth and immersed in near boling water (90°C) removed from the heat source for not more than 30 seconds. Pour off the water. Add cold water (room temperature) 20 times of the seed volume. Let stand overnight to imbibe and sow the seeds in the nursery beds/seed trays. Seed inoculation with appropriate rhizobial strain is recommended before sowing. Mangium seedlings are ready for pricking out in 6-10 days after sowing. Polythene bags are the most common containers used in thetropics for pricking out. Mangium seedlings attain a target size of 25-40 cm height in about 12 weeks. Seedlings are hardened by progressively reducing watering and removing shade in the nursery. If the seedlings have grown larger than the target size in the nursery, they may be lopped.

 

Planting and stand management

Planting is usually done in pits of 20 cm depth and 10-12 cm diameter. In monospecific stands, spacing of 2 m x 2 m or 2.5 m x 2.5 m is common. However, if saw log production (large diameter stems) is the objective, wider spacing (3-3.5 m between rows and between plants) should be followed. In agroforestry situations, spacing within rows and between rows must consider the effect of shade and root competition on the yield of associated crops. Shade tolerant crops such as turmeric and ginger can be intercropped with Mangium trees planted at 2 m x 4 m or 4 m x 4 m spacing. The crops can be raised in one meter wide beds laid in between the planting rows of Mangium.


First weeding must be carried out two months after planting and thereafter at regular intervals depending on weed growth. On favourable sites, mangium plants emerge and dominate the weeds within two years, thus not requiring any further weed control. Fertilizers may be applied @ 30-40 g N, 15-20 g P2O5 and K2O per seedling per year from the second year to the fifth year. Mangium needs regular pruning and thinning if the plantation objective is to produce quality saw logs on 15 to 20 year rotation. These operations in general are not required for pulp wood production on 6 to 8 years rotation. However, multi-stemmed seedlings may be `singled'. In pruning, branches are carefully removed in one or more steps along the bottom trunk up to about 6-7 m height. For saw log production regimes the following silvicultural schedule is recommended. The average wood yield per tree on a 15 years rotation is about 0.7 to 1.0 m3.

Silvicultural management schedule for mangium saw log regime

Age

Activity

Remarks

4 months after planting

General slashing

Uproot all climbers within 45 cm radius of each plant.  Remove branches at height less than 30 cm from the ground.

6 months after planting

General slashing

As above

12 months after planting

General slashing and first pruning

Remove all branches up to 1.5-2.0 m height.

2 years after planting

First thinning and high pruning

Remove 300 trees/ha, retaining 600 trees/ha.  Prune branches up to 6 m height of the 200 selected trees (to be retained till end).

4-5 years after planting

Second thinning

Remove another 200 trees/ha retaining 400 trees/ha.

8-9 years after planting

Final thinning

Remove another 200 trees/ha.

 

Injuries and protection

Although root rot disease caused by Ganoderma sp. (red rot), Phellinus sp. (brown rot) and Rigidoporus lignosus are major problems in mangium stands, there are no specific control recommendations against these fungi. Signs of the disease are evident on the roots after the tree has fallen or upon excavation. Depending on, which fungus causes the disease, there may be dark reddish granular rusty brown encrustation or white thread-like rhizomorphs on the surface of the rots. The usual method of controlling root rot caused by fungi that spread by root contact is to remove and destroy all diseased roots and woody debris.


Chemical protection against pink disease (Corticium salmonicolor), especially in endemic areas, can be achieved by using copper fungicides. The best way to prevent pink disease, however, is to plant tolerant varieties.

 

Progressive decay of the heartwood (heart rot) is another malady afflicting mangium trees. Normally, fungi that decay heartwood do not attack sapwood; such trees continue to grow to maturity and may outwardly appear healthy and vigorous. However, since heart rot is progressive, there will be considerable decay cull at the end of the rotation. A variety of basidiomycete fungi have been associated with this malady. At present there are no control measures against mangium heart rot. The best way is to avoid injury to trees and wound dressing.


Although about 30 insect species are reported to be pests of mangium, only a few such as root feeders, branch and stem borers and the red coffee borer are considered economically important. Root feeders (Sternocera aequisignata) can be controlled by chlorpyrifos application to the soil or seedbeds. To prevent branch and twig borer (Sinoxylon anale) occurrence, remove and burn all broken branches in which breeding takes place. The only effective method to control red coffee borer (Zeuzera coffeae) damage is to inject insecticide into the holes where larvae push out their frass.


Utilization of mangium wood
Timber is used for a variety of purposes like wood-based panels, pulp and paper industry etc. Mangium wood gives attractive furniture, cabinets, moulds and door/ window components. However, the presence of flutes and incidence of rots and termite attack will detract both the quality and quantity of sawn timber from mangium logs. Therefore, mangium has greater potential as a component of composite wood products such as veneer and plywood, laminated veneer lumber, fibre boards etc. and for chemical uses such as pulp, paper and tannin production, besides fuel-wood. 

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