Sabtu, 20 April 2013



Kingdom : Plantae
Sub-kingdom : Tracheobionta
Division : Magnoliophyta
Class : Magnoliopsida
Sub-class : Asteridae
Order : Gentianales
Family : Apocynaceae
Subfamily : Apocynoideae
Genus : Dyera Hook.f.
Species : Dyera costulata (Miq.) Hook. f.

The jelutong (Dyera costulata, syn. D. laxiflora) is a spesies of tree in the oleander subfamily. It originated from Malaysia and it grows to approximately 60 metres (200 ft) tall with diameters of 2 metres (5 to 6 ft), or even to 80 m (260 ft) tall with diameters to 3 m (10 ft), and boles clear and straight for 30 m (90 ft). It grows in Malaysia, Borneo, Sumatra and southern Thailand. Its natural distribution is scattered locales in low-elevation tropical evergreen forest.
Jelutong is used for its wood. Although technically a hardwood it has many properties similar to balsa wood. These properties such as the low density, straight grain and fine texture mean it is easy to work with and popular with model makers. The roots are used as a cork substitute. In addition, jelutong can be tapped for latex and from the 1920's through the 1960's, jelutong latex was an important source of chewing gum.
Jelutong has been traditionally overharvested, and is a threatened species in many areas. However, due to its quick growth, hardy survival, and strong replanting efforts, its extinction is unlikely. It is a protected species in parts of Malaysia and Thailand. The tree is grown commercially for timber. Sawdust from this species has been known to cause allergic dermatitis.

General Characteristics of jelutong's wood:
Heartwood creamy white to pale straw not differentiated from sapwood. Grain mostly straight; texture moderately fine and even; slightly lustrous without taste but has a slight sour odor that is distinctive. Marked with latex traces or canals often in clusters 2 to 3 ft apart along the stem.

Working Properties:
Works easily with hand and machine tools but may gum the cutter excellent for carving; glues satisfactorily.

Other Scientific Names : Dyera laxiflora Hook. f. Alstonia costulata Miq.
Common Names :
Hill jelutong (English)
Jelutong bukit (Indonesia)
Melabuai (Sumatra)
Jelutong bukit (Malaysia)
Teen-pet daeng ye-luu-tong (Thailand)

Peninsular Thailand, Peninsular Malaysia, Singapore, Sumatra, Borneo and intervening islands (Lemmens, Soerianegara and Wong, 1995).

The species occurs in primary evergreen lowland or hill forest, in well-drained locations up to 300 m (Lemmens, Soerianegara and Wong, 1995).

Population status and trends
Jelutong has a scattered natural distibution and has declined as a result of tapping for latex and felling for timber. The risk of extinction was recognised 60 years ago. In Peninsular Malaysia the species has been reported to be threatened (Ng et al 1984). Jelutong does, however, regenerate readily in logged-over forest. It is also planted commercially for timber.

Exploitation for latex, felling for timber, conversion of lowland forests to agriculture.

It has a number of speciality uses such as pattern making in foundry work, for drawing boards, pencils, picture frames, dowels, carving, blackboards, wooden toys, clogs, brush handles and battery separators, and it is also used for furniture parts, door knobs, ceilings, partitioning, matchsticks, matchboxes and packing cases. The roots are used as a substitute for cork and their wood for axe handles. The latex is used in the manufacture of chewing gum, in paints, as priming for concrete, or for sizing paper. Follicles are occasionally used as torches by the local population or burnt to repel mosquitos (Lemmens, Soerianegara and Wong, 1995).
In the period from 1980-1990 the export of jelutong sawn timber from Peninsular Malaysia was 32000-44000m3/year with a value of US$ 5.1-10.8 million a year; in 1992 it was 19000 m3 with a value of US$ 8.3 million (US$440/m3) (Lemmens, Soerianegara and Wong, 1995). In 1995, Malaysia (Peninsular) exported 5000 m3 of sawnwood at an average price of 710$/m3 (ITTO, 1996). The export from Sabah was 67000 m3 in 1987 with a value of US$4.5 million and 23000 m3 (55% as sawn timber, 45% as logs) in 1992 with a total value of US$ 3.5 million (US$ 215/m3 for sawn timber, US$ 82/m3 for logs). Japan imports comparatively large amounts of jelutong, mainly from Sarawak and Sabah (Lemmens, Soerianegara and Wong, 1995). In 1987, Indonesia exported 2,183,462US$ worth of this species as jelutong (WWF and IUCN, 1994-1995).

In Malaysia, the trade in latex has declined since the peak production period 1930-1940. The export of jelutong latex from Indonesia was still around 3500 t in 1989 (Lemmens, Soerianegara and Wong, 1995). Indonesia is the main source of jelutong gum. Most is exported to Singapore, mainly for re-export to the US. Some is exported directly to Japan and Europe where Italy is the main importer (Coppen, 1995).

Conservation measures
Jelutong is subject to a log export ban in Peninsular Malaysia, and special permission has been required to cut the tree in Thailand (Ministry of Agriculture and Cooperatives Decree of 1988).
Regulations on the methods of tapping the latex were introduced in the 1930s (Coppen, 1995).

Forest management and silviculture
In Peninsular Malaysia D. costulata is chosen for enrichment planting because it is easy to handle in the nursery, survives well when planted out, has a good rate of growth and has good market potential. Prolonged contact with acid water in peat forest harms young plants. D. costulata is a very light-demanding species and once a young tree is well established in full light, it tends to spread its crown and develop into a pronounced 'wolf tree'. Sudden opening of the canopy is favourable for its development (Lemmens, Soerianegara and Wong, 1995). D. costulata coppices readily and is extremely resistant to girdling (Lemmens, Soerianegara and Wong, 1995).

This link : The collection of natural gum from Jelutong tree for chewing gum industry

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