5009

5(3): Timber trees; Lesser-known timbers

Bridelia Willd.

Sp. pl. 4(2): 978 (1806).

EUPHORBIACEAE

x = 13; B. retusa, B. stipularis (L.) Blume: n = 13

Indonesia: kanderi (general), kandri (Javanese), kanyere (Sundanese). Malaysia: kenidai, kernam (Peninsular), kerdam (Sarawak). Papua New Guinea: scrub ironbark (En).

Bridelia comprises about 50 species and is distributed in the Old World tropics. Most species occur in Asia, from Sri Lanka, India and the Himalayas to Burma (Myanmar), Indo-China, southern China, the Ryukyu Islands, Taiwan, Thailand, and throughout the Malesian region towards the Solomon Islands, Vanuatu and northern Australia.

The wood of Bridelia is used for temporary construction, agricultural implements, interior trim, light framing, joinery, drawer slides and sides, carts, carving, tool handles and other applications requiring toughness and flexibility. Material for tool handles must be properly selected. The attractively mottled silver grain makes the wood suitable for decorative purposes.
A decoction of the leaves or bark of several species, mainly that of B. tomentosa, is applied medicinally against itch, colic, stomach-ache, fever and dysentery. The leaves are attributed to have purgative, laxative and anti-bacterial properties. The fruits of most species can be eaten raw. Those of B. insulana are applied to colour palm wine red.

Supplies are generally extremely small; this, plus the usual small size of the trees, means that the wood of Bridelia is utilized mainly on a local scale. In 1996 Papua New Guinea exported only 92 m³ of "scrub ironbark"" logs at an average free-on-board (FOB) price of US$ 101/m³.

Bridelia yields a medium-weight hardwood with a density of 450-880 kg/m³ at 15% moisture content; B. glauca and B. insulana are comparatively light and have a density of 450-610 kg/m³ and 530-630 kg/m³, respectively. Heartwood pink with straw-coloured streaks or olive-grey-brown, distinct only in the green condition from the 3 cm wide, yellow-brown or straw sapwood; grain interlocked and sometimes wavy; texture moderately fine and even; attractive mottled silver grain present on radial surface of B. retusa wood; wood very greasy. Growth rings indistinct; vessels moderately small, mostly in radial multiples of 2-several, tyloses present; parenchyma paratracheal vasicentric, usually not visible; rays moderately fine, visible to the naked eye on the transverse surface; ripple marks absent.
Shrinkage upon seasoning is moderate; B. tomentosa is reported to warp badly during drying but B. retusa can be seasoned without serious degrade. The wood is hard, not very strong and fairly tough. It is easy to work with hand and machine tools, but is somewhat fibrous; B. tomentosa wood is reported to be extremely difficult to hand-saw when green. The durability varies from moderately durable to non-durable under exposed conditions. However, house posts made of B. macrocarpa wood reputedly lasted for 10 years, which classifies it as durable. Wood samples are susceptible to attack by ambrosia beetles. The sapwood is susceptible to Lyctus.
The mean fibre lenght of B. tomentosa is 1.160 mm.
See also the tables on microscopic wood anatomy and wood properties.

Usually monoecious shrubs, climbers or small to medium-sized trees up to 20(-30) m tall; bole straight to fairly irregular, branchless for up to 12(-17) m, up to 50(-85) cm in diameter, occasionally with small buttresses up to 1.8 m high; bark surface smooth to prominently longitudinally fissured, flaking in scales or long strips, dark brown to grey-brown, inner bark fibrous, pink. Leaves alternate, distichous, simple, with the lateral veins close, straight and parallel, short-stalked, margin entire to slightly crenate; stipules caducous. Flowers crowded in a small glomerule that is solitary or grouped in a spike and axillary, unisexual, very small, 5-merous; sepals valvate; petals smaller than the sepals. Male flowers with annular or interrupted disk; filaments connate into a column; pistillode present. Female flowers with annular or cupular disk; ovary superior, 2(-3)-locular with 2 ovules in each cell, styles 2, free or variably united, bifid, stigmas terete to flat. Fruit a small, 1-2(-3)-locular drupe with a persistent calyx and 1 seed per locule. Seed with smooth testa. Seedling with epigeal germination; cotyledons emergent, bilobed; hypocotyl elongated; first pair of leaves opposite, subsequent ones arranged spirally, soon distichous.
The larger figures above related to the tree size and bole all refer to B. macrocarpa. In a nursery in India B. retusa seedlings had attained a height of only 8-15 cm after one year and 15-50 cm after two years. In natural forest a mean annual diameter increment of 0.1-0.4 cm has been recorded; a value of 0.5-1.0 cm is known from wood samples.
There is some discussion about the correct spelling of the name Bridelia. According to nomenclatural rules it should be "Briedelia"" but at the time of writing a proposal to conserve the first spelling has been submitted. Bridelia is one of the 2 genera of the tribe Bridelieae (together with Cleistanthus) within the subfamily Phyllanthoideae.

Bridelia is fairly common in secondary, evergreen to semi-deciduous forest, forest margins or scrub vegetation and is found less often in primary forest. It is often associated with streams or rivers and is found in well-drained habitats as well as in peat-swamp forest and occasionally along the edge of mangrove vegetation, from sea-level up to 1800 m altitude. Soil types vary from sandy alluvium to clay soils or black rocky soils. B. tomentosa also occurs in open savanna.

Bridelia can be propagated by seed. For B. retusa 16 000-17 500 pyrenes/kg have been counted. The germination rate of B. insulana is 90-95% in 9-30 days for seeds and 55% in 15-36 days for fruits. B. retusa tolerates moderate shade and regenerates from coppicing and by root suckers.

As Bridelia is fairly common, especially in secondary vegetation, there seems to be little risk of genetic erosion.

Increased utilization is unlikely, but Bridelia wood will probably keep its value for applications where toughness is demanded.

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H.C. Ong

Bridelia glauca
Bridelia insulana
Bridelia macrocarpa
Bridelia pustulata
Bridelia retusa
Bridelia tomentosa

Ong, H.C., 1998. Bridelia Willd.. In: Sosef, M.S.M., Hong, L.T. and Prawirohatmodjo, S. (Editors): Plant Resources of South-East Asia No 5(3): Timber trees; Lesser-known timbers. PROSEA Foundation, Bogor, Indonesia. Database record: prota4u.org/prosea

The following species in this genus are important in this commodity group and are treated separatedly in this database:
Bridelia glauca
Bridelia insulana
Bridelia macrocarpa
Bridelia pustulata
Bridelia retusa
Bridelia tomentosa