6253

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

Schoutenia Korth.

Ned. Kruidk. Arch. 1: 312 (1848).

TILIACEAE

x = unknown; 2n = unknown

Indonesia: walikukun (general). Malaysia: bayur bukit (Peninsular).

Schoutenia comprises 9 species occurring in Burma (Myanmar), Indo-China, Thailand, Peninsular Malaysia, Sumatra, Java, Borneo and the Lesser Sunda Islands.

The hard, heavy and flexible wood of Schoutenia is used for house building, tool handles, agricultural implements, spokes and wheels, poles of vehicles, sporting goods and pegs for boat construction. In Java the wood is used as a substitute for that of Lagerstroemia speciosa (L.) Pers. The wood is also used to produce charcoal.
The bark yields rough rope for binding.

Schoutenia wood is highly valued locally and traded on a local scale, but no exact figures are available. In Indonesia it is classified as a commercial timber.

Schoutenia yields a heavy hardwood with a density of 770-1080 kg/m³ at 15% moisture content. Heartwood purple-grey-brown to dark purple-brown, not clearly differentiated from the sapwood; grain straight or interlocked; texture moderately fine and even. Growth rings indistinct or indicated by darker tissue, sometimes also indicated by marginal parenchyma bands; vessels moderately small to medium-sized, solitary and in radial multiples of 2-4, solitary vessels predominating in some areas, the multiples in others, open; parenchyma abundant, apotracheal diffuse and diffuse-in-aggregates rarely grading into narrow bands, sometimes in marginal or seemingly marginal bands, and scanty paratracheal to vasicentric visible; rays extremely fine to moderately fine, visible with a hand lens; ripple marks present, distinct in S. ovata but reportedly absent for S. accrescens.
The wood is very hard, very strong and extremely tough. Although hard, it is easy to work. It is moderately durable to very durable, even in contact with the ground or when exposed to the weather.
The gross energy value of the sapwood of S. ovata is about 20 070 kJ/kg and of the heartwood about 20 310 kJ/kg.
See also the tables on microscopic wood anatomy and wood properties.

Evergreen or deciduous, small to medium-sized trees up to 35 m tall, rarely shrubs; bole usually fairly short, up to 60(-80) cm in diameter, sometimes prominently fluted or with buttresses up to 1.7 m high; bark surface closely fissured and flaky, dark reddish-brown to greyish-brown, inner bark fibrous, yellowish to reddish or pinkish. Indumentum of stellate hairs or scales. Leaves alternate, distichous, simple, margin entire to sinuate, base usually unequal, 3-veined; stipules caducous or persistent. Flowers in a few-flowered, paniculate or racemose, axillary or terminal inflorescence, bisexual; pedicel jointed; calyx membranous, usually campanulate, (4-)5(-6)-lobed, conspicuously veined, white to yellow; petals usually absent (5 in S. ovata); disk usually present, narrowly annular; stamens 15-many, usually in 5 bundles, persistent; ovary superior, (3-)5-locular with 2 basal ovules in each cell, densely stellate pilose, style 1 with 5 stigmas. Fruit a globular, usually 1-seeded capsule with a strongly enlarged, parachute-shaped, papery calyx and persistent style. Seedling with epigeal germination; cotyledons emergent, bilobed; hypocotyl elongated; first 2 leaves opposite or the first few alternate-spiral, subsequent ones alternate-distichous.
Tree growth is according to Troll's architectural model, characterized by all axes being plagiotropic, the proximal parts becoming erect and forming the main axis. Mean annual diameter and height increment of S. ovata in an 8-year-old plantation were 1.4 cm and 1.5 m, respectively; in a mixed plantation with Dalbergia latifolia Roxb. of 11 years old they were respectively 0.8 cm and 0.8 m. S. accrescens flowers gregariously in March on the bare branches or with the new leaves, whereas fruits are found in April-May. In Java S. ovata flowers in March-June(-November) and ripe fruits can be found in (April-)May-September(-December). In Thailand flowers and fruits are found in September-December. Seed is dispersed by wind or water.
S. accrescens is very variable and can be divided into 2-3 subspecies.

Schoutenia species are locally common and sometimes occur gregariously in moist locations in primary rain forest, up to 900(-1100) m altitude. S. ovata is found in slightly seasonal climates.

Schoutenia may be propagated by seed and by vegetative means. Fruits of S. ovata should be collected from the ground to avoid the inclusion of immature seed. There are about 42 500 dry seeds/kg. After-ripening of the seed is very important and germination is optimal after 3-5 months of storage when collected seeds are exposed daily to sunlight, or after 17 months of storage in airtight containers. Seeds should be sown in full sunlight and show about 30% germination in 7-21 days. Fresh fruits of S. accrescens without a calyx have 2-50% germination in 8-36 days. Fresh fruits of S. kunstleri have about 80% germination in 9-14 days. S. ovata seed over 3 mm in diameter had a significantly higher germination percentage and all the seedlings survived, whereas seedlings from smaller seed all died. Therefore, the small seeds should be discarded. Seedlings of S. ovata can be stumped to leave 20 cm shoot and 20 cm root and a diameter of 0.5-2.5 cm and may attain 90-100% survival. Stem cuttings have also been successful (70-95% survival), whereas the survival for root cuttings was slightly more variable but still 35-90%. S. ovata suckers easily; cut or injured roots produce root suckers profusely. On infertile soils S. ovata grows very poorly, whereas on fertile soils it is generally more economic to grow other species. It should not be planted on marshy soils or where the water table is periodically high. S. ovata has often been used as underplanting in teak (Tectona grandis L. f.) plantations where it grows well. It has occasionally been mixed with Dalbergia latifolia, but the trees bend or die back because of insufficient light. A pure stand was planted at 2 m x 3 m, but this spacing was considered too wide as it took 6 years for the canopy to close. Natural pruning was generally poor, but pruning to improve stem form was successful. The clear bole wood produced in 8 years was 38 m³/ha. S. ovata is also fairly resistant to fire. The walikukun borer (Agrilus kalshoveni) has been a serious pest of S. ovata, locally affecting over 50% of the wild population in East Java in the 1920s. Apparently only individuals that are at least periodically in full sunlight are affected and attacked trees no longer sucker. Many trees died as a result of this pest, but it has not been reported since this single outbreak. A 50-hectare plot in natural lowland forest in Peninsular Malaysia was found to contain 473 Schoutenia trees of over 1 cm in diameter of which 17 trees were over 30 cm in diameter.

Some of the Schoutenia species are endemic and may be vulnerable to genetic erosion by deforestation.

Plantations of S. ovata did not compare favourably with other timber species and are therefore no longer established. The very tough wood from natural forest sources will probably remain locally important.

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R.C.K. Chung

Schoutenia accrescens
Schoutenia buurmanii
Schoutenia kunstleri
Schoutenia ovata

Chung, R.C.K., 1998. Schoutenia Korth.. 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:
Schoutenia accrescens
Schoutenia buurmanii
Schoutenia kunstleri
Schoutenia ovata