Xylocarpus (PROSEA Timbers)

Plant Resources of South-East Asia Introduction

List of species

Xylocarpus J. König

Protologue: Naturforscher (Halle) 20: 2 (1784).

Family: Meliaceae

Chromosome number: x= 26; X. granatum, X. moluccensis: 2n= 52

Vernacular names

• Nyireh (trade name). Mangrove cedar, pussur wood (En)
• Philippines: tabigi (general)
• Thailand: kra buun, ta buun.

Origin and geographic distribution

Xylocarpus comprises 3 species and is found along the coasts of East Africa and Madagascar towards India, Burma (Myanmar), Indo-China, China, the Ryukyu Islands, Thailand, the Malesian region, tropical Australia and the Pacific, east to Tonga and Fiji. All three species are widespread and occur throughout Malesia.

Uses

The wood is used mainly for high-quality furniture and cabinet work, carving and the manufacture of fancy articles. Other reported uses are for light construction, bridge building, interior finish and panelling, flooring, doors, posts, joists, beams, rafters, mouldings, ship and boat building, fence posts, salt-water piling, gun stocks, billiard tables and billiard cue butts, tool handles, tobacco pipes, wooden pins and sliced decorative veneer. In India the wood is regarded suitable for second grade pencils. The wood is sometimes used as firewood and for charcoal production, but these applications are not recommended.

The oil extracted from seeds of X. granatum has been used as an illuminant and as hair oil. Burned seeds of the same species have been used mixed with sulphur and coconut oil against itchy skin. An oil extracted from X. moluccensis seeds is used in the Philippines to treat insect bites. A decoction of the bark is used in the treatment of cholera and is also applied to cure dysentery, diarrhoea and other abdominal troubles, and as a febrifuge. Formerly, the bark was used to make a fairly bitter "palm wine". The bark yields a tannin which has been used quite extensively in Java to tan fishing lines and nets and has been applied to tan heavy hides and to dye cloth umber.

Production and international trade

Xylocarpus wood is generally used on a local scale. Very small amounts of "mangrove cedar" are imported by Japan. In 1996 Papua New Guinea exported only 55 m³of mangrove cedar logs at an average free-on-board (FOB) price of US$ 107/m³.

Properties

Xylocarpus yields a medium-weight hardwood with a density of 615-880 kg/m³at 15% moisture content. Heartwood reddish, darkening to a deep warm brown on exposure, usually sharply demarcated from the narrow, buff-coloured, pale pink or silver-grey sapwood; grain straight or alternating to slightly interlocked; texture fine and even; wood with darker streaks producing attractive watered-silk figure on tangential surfaces; X. moluccensis sometimes with a faint cedar-like odour. Growth rings visible or hardly visible, marked by narrow marginal parenchyma; vessels very small to medium-sized, mostly in radial pairs, occasionally solitary or in radial multiples of up to 4 ( X. granatum ) or more than 4 ( X. moluccensis ), open or filled with dark-coloured, gum-like deposits; parenchyma sparse to abundant, apotracheal in narrow to moderately broad closely-spaced bands and paratracheal vasicentric; rays moderately fine to medium-sized; fine ripple marks present but not always distinct.

Shrinkage is very low to low, the wood seasons well, but is liable to splitting, end-checking and insect attack. Boards of X. moluccensis take about 3 months to air dry when 13 mm thick and about 5 months when 38 mm thick; the wood kiln dries satisfactorily. The wood is moderately hard, moderately strong and tough. It is easy to work and turn, occasionally it is reported as difficult to saw due to interlocked grain, it finishes well and takes a high polish. The pulping and paper making properties of X. granatum are rated as poor. The wood is moderately durable when exposed to the weather or in contact with the ground, and is resistant to pressure preservative treatment. It is resistant to teredo attack in some situations and to dry-wood termites in protected situations. The sapwood is non-susceptible to Lyctus .

The bark of mature trees contains 20-34% tannin on dry matter base. Seeds contain 1-2% oil. The charcoal has a somewhat low density and high burning rate making Xylocarpus an unfavourable source. Firewood burns quickly and produces great heat, which is why other sources are preferred.

See also the tables on microscopic wood anatomy and wood properties.

Botany

Evergreen or sometimes deciduous, monoecious or rarely dioecious, small to medium-sized trees up to 20(-30) m tall; bole crooked ( X. granatum ) to straight and cylindrical ( X. moluccensis ), branchless for up to 10 m, up to 90(-100) cm in diameter, usually with small buttresses and snail roots, those of X. moluccensis bearing many short pneumatophores; bark surface smooth, irregularly flaking, whitish to yellow-brown ( X. granatum ) or rough, longitudinally fissured, flaking into oblong pieces, dark brown ( X. moluccensis ), inner bark green, red or pink; crown narrow and compact to bushy. Leaves arranged spirally, paripinnate with (1-)2-4(-5) pairs of leaflets, exstipulate; leaflets entire. Flowers in an axillary thyrse, 4-merous; calyx lobed; petals free, pinkish-yellow; staminal tube urceolate to cupular bearing 8 anthers; disk cushion-shaped, red; ovary superior, 4(-5)-locular with 3-4(-6) ovules in each cell, style short with a discoid stigma. Fruit a large, tardily dehiscing, subglobose capsule. Seeds 5-20, irregularly tetrahedral or pyramidal, attached to a central columella, with a corky testa. Seedling with hypogeal germination; cotyledons not emergent; hypocotyl not elongated; epicotyl bearing scales followed by simple leaves.

Growth is according to Rauh's architectural model, characterized by a monopodial trunk which grows rhythmically and so develops tiers of branches. Each new flush is marked by a few scales followed by pinnate leaves. In India early growth is rapid, over 60 cm in height in 2 months, and an annual diameter increment of 0.8 cm has been recorded. In Thailand a mean annual diameter increment of 1.3 cm was recorded for trees of approximately 10 cm in diameter. On the other hand, in Bangladesh the annual diameter increment of X. moluccensis was very small being 0.2 cm over a 13-year period. Growth characteristics vary greatly between different provenances. Flowering is usually in March-April; fruiting in June-July. Flowers are pollinated by bees. Usually only one fruit is present per inflorescence. The seeds float just below the water surface and are dispersed by ocean currents.

In the past there was much confusion about which name should be applied to which species. There has been complete confusion in the literature making it sometimes impossible to attribute certain data to a given species. The two most common species ( X. granatum and X. moluccensis ) are easily recognized by their bark features but are difficult to distinguish in the herbarium. X. rumphii can be recognized by its ovate to cordate leaflets.

Ecology

Xylocarpus species are locally common in mangrove swamps, beaches and coastal woodlands on rock, sand and other substrates, generally on locations only flooded at exceptionally high tides. They occur in areas with seasonal climates as well as in those with non-seasonal climates. X. moluccensis is found in the Bruguiera gymnorhiza (L.) Savigny type of mangrove forest. X. granatum is often associated with Nypa and Sonneratia species and may be locally gregarious. X. granatum tolerates a salinity of 0.1-3%. Xylocarpus is a moderate light demander, enduring more shade when young than it does later on. A decrease in freshwater supply during the dry season can result in high mortality.

Silviculture Xylocarpus may be propagated by seed. Seeds of X. granatum have about 70% germination in 1-2.5 months. Seed viability decreases rapidly upon storage. Seed should to be sown with the convex side upwards. Seedlings can attain 50 cm height in 3 months. Direct sowing has been successfully applied in a trial plantation of X. granatum at 1 m × 1 m. In Aceh (Sumatra) natural regeneration in mangrove forest is good, but X. granatum is cut to allow the more valued Rhizophora spp. to become dominant. It is also reported that roots of X. granatum tend to promote silting up and thus raise the soil level. This, plus the dense crown of X. granatum , hampers the adequate regeneration of Rhizophora . In Peninsular Malaysia Rhizophora and Bruguiera species are considered more valuable in the mangrove forest and Xylocarpus is considered of no economic importance. Large trees are often hollow and it is difficult to obtain large sizes for conversion to timber. Moreover, X. granatum trees are often crooked and gnarled, which further limits their use for sawn timber. X. moluccensis is generally straight-stemmed and reproduces by coppice. Like other Meliaceae of the subfamily Swietenioideae , Xylocarpus is also attacked by Hypsipyla shoot borers. To obtain tannin, the bark is peeled off but the trees recover easily.

Genetic resources and breeding

All three Xylocarpus species are comparatively common and widespread and do not seem endangered, except that mangroves are being cleared locally for other uses.

Prospects

Given the desirability of wood of X. moluccensis for high quality furniture and cabinet work, it is worth considering the cultivation of favourable provenances in dry mangrove areas. However, much more needs to be known about its growth and silvicultural aspects. Xylocarpus may also be used increasingly for reforestation and afforestation of coastal wetland.

Literature

40, 70, 124, 151, 162, 163, 267, 300, 341, 348, 371, 387, 390, 436, 464, 526, 536, 568, 632, 663, 696, 732, 780, 829, 831, 845, 846, 878, 880, 933, 934, 951, 993, 1008, 1038, 1052, 1056, 1066, 1071, 1098, 1101, 1104, 1168, 1189, 1221, 1239, 1242.