28

5(2): Timber trees; Minor commercial timbers

Bischofia Blume

Bijdr. fl. Ned. Ind., part 17: 1168 (1827).

EUPHORBIACEAE

x = unknown; Bischofia javanica: 2n = 98

Trade groups Bishop wood: medium-heavy hardwood, a single species: Bischofia javanica Blume, Bijdr. fl. Ned. Ind., part 17: 1168 (1827).

Bishop wood: Java cedar (En). Bois de l'évéque (Fr). Indonesia: gadog (general), gintungan (Javanese), kerinjing (Sumatra). Malaysia: jitang (Peninsular), tuai (Sabah). Papua New Guinea: Java cedar. Philippines: tuai (Filipino). Laos: 'khom 'fat, 'foung 'fat. Thailand: toem, pradu-som (general). Vietnam: nhoi.

Bischofia comprises 2 species. One occurs in China only. The other (Bischofia javanica) is much more widespread and is found from India and the Himalaya to China, Taiwan, southern Japan, Indo-China, Thailand and throughout the Malesian area (but rare in Peninsular Malaysia and large parts of Borneo) towards north-eastern Australia and the Pacific east to Samoa and Tonga. It is locally planted as a timber plantation species and as an ornamental in its natural area of distribution (e.g. near Medan, Sumatra), and has been introduced as a fast growing ornamental tree in East Africa and South Africa, and in the United States (California, Florida) where it has become a weed.

Bishop wood is used for general construction (beams, posts), bridges, decking, sleepers, mining props, flooring, interior finish, joinery, furniture, lining, agricultural implements, charcoal, carving, pencils and billiard cue butts. It is a potential source of long fibres for pulp and paper production, and is also suitable for the production of veneer and plywood, and charcoal.
In India, it is considered to be an excellent shade tree in coffee and cardamom plantations. In Polynesia, a red dye is extracted from the bark. The bark also contains tannin, used for toughening nets and ropes.

No statistics are available on international trade of Bishop wood, but it is regarded as a commercial hardwood in Papua New Guinea. The wood is probably mostly consumed locally.

Bishop wood is medium-weight and moderately hard to hard. The heartwood is purplish-brown to reddish-brown and is sharply differentiated from the narrow, pale brown to pale reddish-brown sapwood. The density is 520-1010 kg/m³ at 15% moisture content. The grain is generally interlocked, texture moderately fine to rather coarse and even. The wood surface is rather dull to slightly glossy. Fresh wood smells of vinegar.
At 12% moisture content, the modulus of rupture is 102-111 N/mm², modulus of elasticity 10 500-11 455 N/mm², compression parallel to grain 45.5-59.5 N/mm², shear 17-21 N/mm², cleavage 83 N/mm radial and 118 N/mm tangential, Janka side hardness 7445-8180 N and Janka end hardness 9645-11 325 N. See also the table on wood properties.
The rates of shrinkage of Bishop wood are moderate to high: from green to 12% moisture content 1.0-2.6% radial and 3.2-6.2% tangential, from green to oven dry 3.9% radial and 7.5% tangential. It is difficult to season Bishop wood, because of its tendency to check, split and warp, especially in back-sawn boards. Defects may be diminished by quarter sawing. Air drying 2 cm thick boards from green to 30% moisture content takes 2 months. Kiln drying requires a mild schedule. A dry bulb temperature of 38-60 °C and a corresponding relative humidity of 86-38%, or 41-57 °C and 60-15%, respectively, are recommended.
Bishop wood is rather difficult to saw when dry, but it seems to be fairly easy to saw green. It can be bored and mortised with very good results; planing, shaping, turning and sanding give good to very good results. Good veneer can be produced at a peeling angle of 92° without pretreatment, but the veneer is wavy after drying. Gluing the veneer with urea-formaldehyde produces a plywood complying with the Japanese standard. Sulphate pulping yields a pulp with a high overall strength; hence a strong paper can be manufactured from Bishop wood.
Bishop wood is classified as moderately durable to durable. It is susceptible to Lyctus and dry-wood termite attack, whereas its susceptibility to wood-rotting fungi varies from not resistant to resistant. Longhorn and ambrosia beetles have also been recorded in Bishop wood. The heartwood is difficult to treat with copper-chrome-arsenic preservative by the vacuum-pressure process, but the sapwood can be easily penetrated by preservatives. Hot soaking on an experimental scale for 1, 3 and 5 hours using BFCA resulted in penetrations of 3.7, 4.5 and 5.4 mm with retentions of 2.8, 2.2 and 2.3 kg/m³, respectively.
Bishop wood contains 49-51% cellulose, 23-42% lignin, 9.7-14.4% pentosan, 0.4-1.1% ash and 0.4-1.7% silica. The solubility is 1.4-8.0% in alcohol-benzene, 4.1% in cold water, 5.0-5.8% in hot water and 11.1-29.4% in a 1% NaOH solution. The wood is not very suitable as a fuelwood. The bark contains about 16% tannin.

Dioecious, usually deciduous, medium-sized to fairly large, occasionally large trees up to 35(-50) m tall; bole straight or poorly shaped, branchless part usually short but sometimes up to 20 m long, up to 80(-170) cm in diameter, sometimes with steep buttresses up to 3 m high; bark fissured and scaly with small thick shaggy scales, reddish-brown to purplish-brown, inner bark fibrous, spongy, pink, exuding a red sap; crown dense and rounded. Leaves arranged spirally, pinnately 3-foliolate, glabrous; petiole 8-20 cm long; stipules oblong- triangular, papery, 7-22 mm long, early caducous; leaflets elliptical to ovate, 6-16 cm x 3-10 cm, base rounded to broadly cuneate, apex acuminate, margin finely crenate-serrate, pinnately veined, shiny above, terminal leaflet long-stalked. Flowers unisexual, actinomorphic, 5- merous, small, greenish, apetalous; disk absent. Male flowers in an axillary, many-flowered, 9-20 cm long panicle; sepals united at base, hooded; stamens 5, free, opposite to the calyx lobes; pistillode broadly peltate and short-stalked. Female flowers in a lax, 15-27 cm long panicle; calyx lobes 5, caducous; staminodes very small; ovary superior, globose, 3(-4)-celled, with 2 apical pendulous ovules per cell, style short, with 3 long and spreading to recurved stigmas. Fruit a globose drupe, indehiscent, 1.2-1.5 cm across, bluish-black, with a horny to leathery pericarp and fleshy mesocarp; cells 1-2-seeded. Seed oblong to obovoid, about 5 mm long, brown. Seedling with epigeal germination; cotyledons leafy, petiolate; first few leaves simple, next ones unifoliolate, subsequent ones (from about the 10th leaf) 3-foliolate.

- Macroscopic characters: Heartwood purplish-brown or dark reddish-brown or brown, distinctly demarcated from the pale cream-coloured to reddish-brown or pink sapwood. Grain usually interlocked. Texture medium; wood slightly lustrous. Growth rings indistinct; vessels barely visible to the naked eye, easily seen with hand lens; parenchyma not distinct; rays narrower than vessels; ripple marks absent.
- Microscopic characters: Growth rings absent. Vessels diffuse, 5-20/mm², solitary and in radial multiples of 2-4(-5), radial multiples of 4 common in some samples, solitary vessels oval in outline, average tangential diameter 140-160 µm, maximum tangential diameter 200 µm; perforations exclusively simple; intervessel pits alternate, non-vestured, polygonal, 10-14 µm; vessel-ray pits coarse with reduced borders or simple, elongated and scalariform to more or less circular or irregular in outline; helical thickenings absent; thin-walled tyloses common. Fibres 1200-3200 µm long (2100-2500 µm on average), septate, mostly medium thick-walled, with a few conspicuous simple pits in the radial walls. Axial parenchyma absent to rare, with an occasional cell touching a vessel. Rays 3-7/mm, tending to be of 2 sizes, 1-seriate and 4-5(-6)-seriate, total multiseriate ray height, including uniseriate margins, up to 2-3 mm, range of the height of the multiseriate portion of the ray 200-1500 µm (550-700 µm on average), multiseriate rays heterocellular with 1-10 rows of upright cells, sheath cells sometimes present, uniseriate rays common and composed of upright cells (rays generally conform to Kribs type heterogeneous I and II). Solitary prismatic crystals common in upright and square ray cells, cells with crystals non-chambered or with 2-4 chambers. Oil cells, canals and storied structure absent.

The seedlings show a fast root growth. The taproot is tuberous for a short length and then tapers quickly. Thin but long secondary roots are present below the collar region.
Growth is comparatively slow during the first 3 years, becoming fairly rapid in subsequent years. Under normal conditions, an average annual diameter increment of 1.0 cm and an average annual height increment of 1 m can be obtained. Exceptions have been reported, e.g. a diameter at breast height of 41 cm for 18-year-old trees and a height of 7.5 m for 3-year-old trees and of 10 m for 6-year-old trees.
Bishop wood flowers every year from an age of about 8 years onward. In West Java, flowering usually takes place in August-November(-December) and mature fruits can be found in (January-)February-June with a peak in March. In Central Java, the fruiting period is from May-November, in East Java from November-December.

Bischofia is an aberrant genus within the Euphorbiaceae, mainly because of its pinnately 3-foliolate leaves and fleshy, indehiscent fruits, and has alternatively been accommodated into a plant family of its own (Bischofiaceae) or in the Staphyleaceae. However, embryological and leaf anatomical evidence support its position within the Euphorbiaceae, where it is regarded as the only genus of the tribe Bischofieae within the subfamily Phyllanthoideae.

Bishop wood prefers areas with a more or less distinct dry season (climate types B and C). Its altitudinal range is from sea-level to 1800 m. Bishop wood is fairly common but usually found scattered in primary and old secondary dry and deciduous forest or monsoon forest but also in evergreen forest, swamp forest and teak forest, sometimes in more open places like savanna tracts. It is most frequent on river banks, shady ravines and prefers deep, loose soils such as sandy, rocky or loamy soils with sufficient water content; occasionally it is found on limestone. In the monsoon forest of Timor, Bishop wood has been found in association with Alstonia scholaris (L.) R.Br., Cordia subpubescens Decne., Exocarpos latifolia R.Br., Ficus saxophila Blume, Tetrameles nudiflora R.Br. and Toona sureni (Blume) Merr.
Bishop wood is reported to be the only tall tree of secondary forest in the Philippines.

Bishop wood can be propagated by seed, wildlings and stem cuttings. One kg contains 61 500-90 000 dry seeds. Seed may be collected in large quantities and can be stored for up to 6 months. Bishop wood is well suited for large-scale plantations. Seed may be sown under shade or in full sunlight, provided watering is adequate. Germination starts 1-3 weeks after sowing and after 5-6 weeks about 70% of the seed has germinated. Young plants need plenty of water; therefore, direct sowing in the field is not appropriate. In India, 7-month-old seedlings attained a height of 50-80 cm and containerized and bare-rooted seedlings planted under shade in the field showed 90% and 50-70% survival, respectively.
Stumps should be robust, at least 2.5 cm in diameter, to give a survival of close to 100%. Recommended shoot and root length are 20 cm and 30 cm, respectively. The survival rate drops sharply when thinner stumps are used.
In Java, Bishop wood has been planted in pure stands at 2 m x 3 m, and in mixed plantations in alternating rows with Calophyllum inophyllum L. and Bombax ceiba L. at 1 m x 3 m, and with Acacia mearnsii De Wild. at 2.5 m x 5 m. Survival rates of wildlings and stumps with a shoot length of 20 cm and a root length of 30 cm are close to 100%.

Self-pruning of thick branches in Bishop wood is good once the canopy of the stand closes, which is at least 5 years or more after planting at a spacing of 2 m x 3 m. Planting at a closer spacing is recommended to reduce this period. Pruning wounds heal very well; the tree may survive girdling involving the removal of a strip of bark 30 cm wide. The tree may develop forks as a result of attacks by top and twig-boring insects.
Roots spread out superficially and the tree sprouts vigorously after cutting, making it difficult to eradicate.

In Java, young trees are heavily attacked by top and twig-borers, causing failure of plantations in less suitable locations. On favourable sites, the trees can grow rapidly and survive attack. Caterpillars of Metanastria hyrtaca and Selepa celtis are found feeding on the foliage of Bishop wood. In Indonesia, fungi reported to attack the trees are Corticium salmonicolor and Glomerella cingulata, of which the conidial state is Colletotrichum gloeosporioides. In southern China, Bishop wood has suffered severely from witches' broom.

In Java, an 8-year-old pure plantation on a moderately fertile soil and with a planting space of 2 m x 3 m yielded 12 m³/ha of clear- bole wood.

Bischofia javanica has a large area of distribution and is planted in trial plantations, so it does not seem to be endangered. No conservation of genetic material in germplasm or seed banks, nor any activities related to breeding have been reported.

Because it frequently contains defects and has interlocked grain, the timber of Bishop wood is less suitable for sawnwood applications. However, good-quality plywood and paper can be manufactured from it and Bishop wood shows several positive features for the establishment of plantations, in pure or mixed stands. Breeding borer-resistant trees would make it more worthwhile to plant Bishop wood on less favourable soils. More research is needed into silvicultural aspects.

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B. Sunarno (general part), A. Martawijaya (properties), E. Wheeler (wood anatomy)

Sunarno, B., Martawijaya, A. & Wheeler, E., 1995. Bischofia Blume. In: Lemmens, R.H.M.J., Soerianegara, I. and Wong, W.C. (Editors): Plant Resources of South-East Asia No 5(2): Timber trees; Minor commercial timbers. PROSEA Foundation, Bogor, Indonesia. Database record: prota4u.org/prosea