| Eusideroxylon | |
|---|---|
 | |
| Young tree ofEusideroxylon zwageri | |
Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Magnoliids |
| Order: | Laurales |
| Family: | Lauraceae |
| Genus: | Eusideroxylon Teijsm. &Binn. |
| Species: | E. zwageri |
| Binomial name | |
| Eusideroxylon zwageri Teijsm. & Binn. | |
| Synonyms[2] | |
Bihania borneensisMeisn. | |
Eusideroxylon is a genus ofevergreentrees of the familyLauraceae. The genus ismonotypic, and includes one accepted species,Eusideroxylon zwageri. It is known colloquially in English asBornean ironwood,[3]billian, orulin.[3]
It is native toBorneo andSumatra,[2] where it grows in lowland rain forests.[1]
Eusideroxylon are hardwood trees reaching up to 50 metres in height with trunks over 2 metres (6 ft 7 in) in diameter, producing commercially valuable timber.[citation needed] The wood ofE. zwageri is impervious to termites, and can last up to 100 years after being cut.[citation needed] Due to extensive logging, it is listed asvulnerable in theIUCN Red List.[1]
Eusideroxylon are canopy tree species with erect or spreading branches and extremely durable and decay-resistant wood.
Eusideroxylon zwageri is a slow growing (0.5 metres per year)[4][5] tall evergreen tree with a straightbole (usually host toCassytha, a parasitic vine with leaves reduced to scales, up to half of the tree's height). It is slightly fluted at the base, up to 150–220 cm in diameter. Thetrunk has many small, roundedbuttresses that give the base anelephant-foot like appearance. Individual trees may reach an age of 1,000 years or more. Common commercially exploitable trees attain a height of 30 or more metres (100 ft) with trunk diameters of exploitable trees up to 92 cm (36 inches). Protected trees are towering giants of the forest attaining a height of up to 50 metres and a diameter of 220 cm – though height is routinely reduced by lightning strikes.[6] An Ulin tree discovered in 1993 inKutai National Park, is one of the largest plants inIndonesia. It is an estimated 1,000 years old, and has increased its diameter from 2.41 to 2.47 metres in the 20 years since its discovery. Its height was however reduced from some 30 metres to only 20 after a lightning strike.[4] Another at Sangkimah in the west of the park has a diameter of 2.25 metres and a height of some 45 metres.[7]
The color of the flowers is pale yellow to yellow. The flower is hermaphrodite, actinomorphic, with 6tepals, distributed in twowhorls that overlap. There are sixstaminodes, threestamens, and a simplepistil that consists of one carpel.[8]Pollination is done bybees and otherinsects.[citation needed] The fruits aredrupes, varying in size and shape from oblong to ovate or sub-cylindrical to asymmetric elongated or rounded. They are 8–13 cm long, 4–5 cm in diameter, and weigh 90g-170g.Seed dispersal is by vertebrate animals such as birds, monkeys, bats and rodents, for which the fruits are an important food source.[citation needed]
The trees' leaves are dark green, simple, leathery, elliptical to ovate, 14–18 cm long (5.5–7.5 inches) and 5–11 cm wide (2–4 inches), and are alternate, rarely whorled or opposite, withoutstipules andpetiolate. The leaf blade isentire (unlobed or lobed inSassafras) and occasionally withdomatia (crevices or hollows serving as lodging formites) inaxils of main lateral veins (present inCinnamomum).[9] Young leaves are reddish brown to yellowish red. They have a generous layer of wax, making them glossy in appearance, and are narrow, pointed oval in shape with anapical mucro, or 'drip tip', which enables the leaves to shed excess water in a humid environment.[citation needed]
Timber segments collected from 15 logged stumps in Kubah National Park, Sarawak, Malaysia, found thatE. zwageri can live more than 1000 years[10] and that the growth rate of this species is very slow, with a mean radial growth rate of 0·058 cm y-1. The cutting of old trees ofE. zwageri results in the species being replaced by faster growing species.[10] The long life span and reduced growth rate of this species may be a result of its dense and durable wood containing abundant defensive compounds.[10]
The nameEusideroxylon is Latinized Greek, derived from Greeksideros meaning iron,[11]xylon meaning wood,[11] with the prefixeu- meaning good, true, original.[11] The name of the genus thus means "true iron wood".
Eusideroxylon zwageri seedlings require some shade, while older trees need plenty of light.[12] It can be found in valleys and on hillsides and even on low ridges when soil moisture is sufficient at elevations between sea level and 625 m. The standing timber volume of trees with a diameter of over 50 cm may be as much as 90–112 m3.[citation needed]
Eusideroxylon zwageri has a very slow growth rate ofmeanradial growth of 0.058 cm per year[citation needed]. It is a canopy species in primary forests. The species is considered unsuitable for large-scale plantations due to slow growth and inadequate seed and seedling supply. Manual selection of trees in natural forests is common.[12][13]
Theheartwood when cut is coloured light brown to almost bright yellow. During the aging process theheartwood darkens to deep reddish brown, very dark brown or almost black. Thesapwood is bright yellow when cut, and darkens slightly. The wood texture is fine and even, with a straightgrain or only slightly interlocked. The timber retains a pleasant lemon odour. This odour, along with the woods' natural high lustre, make it prized by cabinet-makers and fine furniture craftsmen.[citation needed]
The wood is dense, and texture is moderately fine to fine and even. Also attractive to users is the resistance toinsects,bacteria,fungi andmarine borers.[9] The wood has anti-bacterial properties (for local medicinal use)[14]Vessels are diffuse-porous, medium-sized and generally evenly distributed, arranged in short radial rows (2–3 vessels). Moderate abundancy of aliform paratracheal parenchyma. Growth rings boundaries are indistinct or absent.Tyloses are often present.[9]
The wood has a radial shrinkage rate of 2–4.5% and a tangential shrinkage rate of tangential 4.5–7.5%. Thetimber dries slowly, and care is needed to avoid checks and splits. The wood is famed for its easy working characteristics, despite high density. The woodplanes,bores andturns cleanly, producing smooth and often lustrous surfaces. Nailing requires pre-bores prior to nailing.Saw blades and other cutting instruments are moderately blunted during working the timber. The wood is apparently difficult toglue withsynthetic resins.[9]
Heartwood is rated as very durable – immune totermite attack;service life of up to 100 years in direct soil contact and more than 20 years for marine work in tropical waters has been reported.[citation needed]
Due to the excellent resistance tobacterial,fungal,insect andmarine borer attack the wood is highly prized for many outdoor uses, especially as decking. Additionally, the wood's high density and easy workability lend it to particularly desirability in maritime structures,dock construction andship building, especially Indonesia'spinisi sail-boat.[15]Common local uses include: House construction, door construction,water butts andtroughs, boat building (Pinisi),tools,tool handles,talisman,jewellery, medicinal slivers (for wounds, cuts, abrasions, bites and tooth-ache/infection), bridges,blowpipes and spear shafts.[citation needed]
Internationally, it is renowned for heavy construction such as a buffer between transportation trailers and heavy steel fabrications (such asboilers,pressure vessels, reactors and many others). It is also frequently found indry docks as a timber to separate thehull ofships from the steel supporting stands. Other uses include use in boats and ships, industrial flooring, roofing (asshingles), fine indoor and outdoor furniture,coffin wood (esteemed by Chinese due to ability to withstand rot and insect attack) and tool handles (especially those exposed to continual high impact (the wood does not splinter and thus injure hands, eyes or endanger the operator on catastrophic failure) such asshovels,axes,block splitters,sledge hammers, heavymallets,demolition hammers,mattocks,picks,hoes andhammers). Some expertcabinet-makers treasure anulin-headedcarpenter's mallet as an excellent intermediate density hammer face between the usual wood and a metal one and is able to quite easily tap or "whack" stubborn highly polished metal fixtures without damage to the face or the fixture.[citation needed]
Other sources indicate thatulin wood is often used for marine constructions such aspilings,wharfs,docks,sluices,dams, ships, bridges, but also used for power line poles,masts, roof shingles and house posts and to a minor extent as frame, board, heavy duty flooring, railwaysleepers, fencing material, furniture etc.[citation needed]
The government ofIndonesia and the state government ofSarawak have formally banned the export of this species.Illegalsmuggling continues to be a major problem.[16]
Conservation efforts are underway, with several countries banning imports.[citation needed]
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