Toona (PROSEA)

Plant Resources of South-East Asia
Introduction

Toona (Endl.) M.J. Roemer

Protologue: Fam. nat. syn. monogr. 1: 131, 139 (1846).

Family: Meliaceae

Chromosome number: x= 13, 14, 23;T. ciliata: 2n= 52, 56, 78,T. sinensis: 2n= 46, 52, 56

Trade groups

Surian: lightweight hardwood, e.g. Toona ciliata M.J. Roemer, T. sinensis (Adr. Juss.) M.J. Roemer, T. sureni (Blume) Merr.

The name surian is also used for the wood of other Meliaceae genera such as Aglaia and Chukrasia , and sometimes also for Anacardiaceae (e.g. Parishia , Spondias ) and Burseraceae (e.g. Santiria ).

Vernacular names

Surian: toon (general)
Indonesia: suren (general)
Papua New Guinea: red cedar
Philippines: kalantas (general). Burma (Myanmar): thitkado
Cambodia: chomcha
Thailand: yom-hom (general)
Vietnam: lát khét.

Origin and geographic distribution

Toona consists of 4 or possibly 5 species and is distributed from Pakistan and China to Australia, and occurs widely throughout Malesia, where 3 or 4 species are found. Fossil records from France, Bulgaria, Japan and India show that the area of distribution used to be much larger. Some species are widely cultivated in the tropics for timber or as ornamentals.

Uses

Surian is considered a valuable timber tree, yielding comparatively soft, fragrant wood which is easy to work. The timber is highly prized and seriously overexploited, first in Australia where it once was the most important native timber. Nowadays it is also heavely exploited in many areas in South-East Asia. It is used for light construction work, furniture, joinery, cabinet work, tea-chests, decorative panelling, ceiling boards, packing cases, cigar boxes, ornamental boxes, bent work, boat and canoe building, paddles, oars, piano cases, musical instruments, face veneer, plywood, carving and sculpture.

The wood is used for shiitake mushroom culture. Surian trees may also be planted for ornamental purposes e.g. in roadside plantings, as firebreaks and for reforestation. The leaves are used locally as a vegetable and forage. Some extracts from the bark and the leaves have insect-repellent properties. The bark and leaves are used in traditional medicine. The bark contains tannin which may be used in the preparation of leather, and has been traditionally used for twines and the manufacture of string bags. The flowers are used in India to prepare a red or yellow dye. An aromatic oil can be extracted from the fruits.

Production and international trade

Japan imports small amounts of surian from Sabah, Sarawak and Papua New Guinea. T. calantas timber is important in the Philippines: in 1981 about 6000 m³of sawn timber was exported with a value of US$ 708 000, and in 1987 about 4650 m³with a value of US$ 671 000 (US$ 144/m³).

Properties

Surian is a lightweight and comparatively soft wood. The heartwood is pale red to reddish-brown, darkening to dark red-brown on exposure, clearly demarcated from the grey-white, pink or pale red sapwood. The density is 270-530(-670) kg/m³at 15% moisture content. The grain is straight to interlocked, sometimes wavy, texture rather coarse and uneven. The wood often has an aromatic cedar-like odour.

At 15% moisture content, the modulus of rupture is 42-85 N/mm², modulus of elasticity 7115-10 700 N/mm², compression parallel to grain 21.5-45 N/mm², compression perpendicular to grain 2-7 N/mm², shear 3-9 N/mm², cleavage 32-43 N/mm radial and 36-51 N/mm tangential, Janka side hardness 1215-3960 N and Janka end hardness 2585-4605 N.

The rates of shrinkage are moderate to fairly high: from green to 12% moisture content 1.1-4.0% radial and 2.6-7.0% tangential, and from green to oven dry 2.1-5.0% radial and 3.6-8.2% tangential. In Malaysia surian timber is reported to dry rapidly, with only slight warping. However, elsewhere it is reported that the timber is somewhat refractory in drying and prone to warping, collapsing and cupping, particularly in thin planks. Close spacing of stickers and weighting of stacks is recommended. Boards 25 mm thick take 1-3.5 months to air dry. In Malaysia, kiln schedule J is recommended; boards 25 mm thick can be kiln dried from 50% to 10% moisture content in 3-6 days without any degrade.

The wood is easy to saw, cross-cut and plane and the planed surface is smooth; it takes a good polish. Some material tends to produce a woolly finish and it is therefore essential to use sharp tools. Mortising, turning and sanding give moderate results, but boring sometimes gives poor results. The gluing and nailing properties are rated as good, but the nail-holding power is moderate. The timber peels well and produces good-class veneer with a nice figure. It can be peeled into 1.5 mm thick veneer at a 90peeling angle without pretreatment. Sometimes logs are liable to lateral and end splitting which may result in the veneer breaking during peeling. Surian veneer glued with urea-formaldehyde produces plywood complying with the German standard.

In Malaysia, surian wood is rated as non-durable. Reports from elsewhere indicate that the heartwood is moderately durable but susceptible to drywood termite and borer attack. The heartwood is resistant to impregnation with preservatives or may show an unsatisfactory penetration pattern, but the sapwood is permeable. Wood dust may irritate the mucous membranes or induce bronchitis or dermatitis.

Wood of T. sureni contains 61% cellulose, 27% lignin, 11.5% pentosan, 0.8% ash and 0.5% silica. The solubility is 2.3% in alcohol-benzene, 3.0% in cold water, 6.5% in hot water and 10.2% in a 1% NaOH solution. The energy value of the wood is about 21 870 kJ/kg.

Description

Monoecious, deciduous or semi-evergreen, medium-sized to fairly large trees up to 40(-60) m tall; bole branchless for 25 m or sometimes more, buttresses absent or small, up to 1.5 m high; bark surface usually fissured, sometimes flaky, and of varying colour, but most oftengreyish-brown, bark with a strong aromatic or offensive smell, slash varying in colour from pink to dark red; crown usually umbrella-shaped and of moderate density, with long and straight branches.
Leaves large and pinnate, arranged spirally, often clustered at the ends of twigs, usually paripinnate, but sometimes with terminal leaflet, without stipules; leaflets subopposite or arranged alternately, entire, serrate or dentate, with 10-20 pairs of secondary veins, usually only slightly pubescent on the veins, often with club-shaped glands and domatia.
Inflorescence in leaf axils at the apex of branchlets, paniculate, much-branched and pendulous, with cymose ultimate ramifications.
Flowers small, 5(-6)-merous, functionally unisexual, terminal flower of a cymule generally female, other two flowers male, dull white, greenish-white to pale yellow or pink, strongly smelling; calyx small, sepals free or united at base; petals free, much longer than calyx, imbricate in bud, usually thick and fleshy, spreading; disk prominent, cushion-shaped; stamens 5, sometimes alternating with staminodes, free, anthers dehiscent throughout their length and introrse; ovary superior, (4-)5-locular, with 6-10 anatropous ovules arranged in 2 rows in each locule, style 1, short, with fleshy and discoid stigma on top.
Fruit a pendulous, ellipsoid or obovoid capsule, membranaceous to thinly woody, with central columella, dehiscing by 5 valves from apex to base.
Seed numerous, winged at both ends or only at upper end; cotyledons foliaceous, endosperm thin, radicle laterally exserted.
Seedling with epigeal, phanerocotylar germination, first leaves opposite and trifoliolate with lobed or dentate leaflets.

Wood anatomy

Macroscopic characters:

Heartwood pale red to reddish-brown, darkening to dark red-brown on exposure, clearly demarcated from the greyish-white, pink or pinkish-red sapwood. Grain straight, interlocked or sometimes wavy. Texture rather coarse and uneven; prominent growth ring figure present on flat-sawn surfaces; wood somewhat lustrous, feeling dry, fragrant with cedar-like scent, with characteristic acrid taste. Growth rings distinct, delimited by a zone of large earlywood vessels, visible to the naked eye; vessel lines conspicuous on longitudinal surfaces, deposits of reddish-brown gum common, tyloses absent; parenchyma vasicentric and terminal, the vasicentric parenchyma inconspicuous, the terminal distinct; rays of one kind, visible to the naked eye; ripple marks absent; axial intercellular canals of the traumatic type occasionally present.

Microscopic characters:

Growth rings distinct. Wood ring-porous. Vessels 20-30/mm²in the latewood zone and (8-)9-12(-15)/mm²in the earlywood zone, solitary and in radial multiples of 2-3(-4), generally round to oval, average tangential diameter of earlywood vessels (300-)470-480μm, of latewood vessels 55-130μm; perforations simple; intervessel pits alternate, with coalescent apertures, (3-)5-8μm in diameter; vessel-ray and vessel-parenchyma pits similar but half-bordered; reddish-brown deposits frequent, chalky deposits occasionally present; tyloses scarce to absent. Fibres 0.4-1.4(-1.9) mm long, non-septate, thin-walled to moderately thick-walled, with minute simple to narrowly bordered pits mainly confined to the radial walls. Parenchyma both apotracheal and paratracheal; apotracheal parenchyma mainly confined to the ring boundary and appearing as terminal bands of 4 or more cells wide, strand length 3-6(-8) cells; paratracheal parenchyma vasicentric as narrow borders to the vessels. Rays (3-)4-8(-14)/mm, (1-)2-4(-5)-seriate, up to 0.5 mm high, heterocellular with 1-4 rows of square to upright marginal cells. Silica bodies absent. Axial intercellular canals of the traumatic type occasionally present.

Species studied: T. ciliata , T. sinensis , T. sureni .

Growth and development

The development of seedlings is rather slow during the first year (up to 30 cm tall), but the mean annual diameter increment is 0.8-1.8(-2.5) cm in T. ciliata plantations of up to 22 years old, with mean annual height increment of 0.9-1.4(-1.8) m. In two plantations of T. sureni in Java of 14 and 17 years old, mean annual diameter increment was 1.4 cm and 1.2 cm and mean annual height increment 1.5 m and 1.2 m, respectively. The mean annual height increment of a 7-year-old plantation of T. sinensis was 1 m. In Peninsular Malaysia, T. sureni grows considerably faster than T. sinensis . T. ciliata planted in Africa had an average height of 35 m and an average diameter of 70 cm at the age of 40 years.

In areas with a marked dry season all the foliage is shed for a part of the year. The flowers are functionally unisexual, but usually with well-formed vestiges of the opposite sex present. In female flowers the anthers do not open and are shrivelled, in male flowers the ovary has vestigial ovules. Fruit bearing is irregular and for T. calantas in the Philippines there may be at least four years between consecutive fruiting years. In Java, T. sureni flowers in May and bears fruits from July to October and in the Philippines T. calantas flowers in March and fruits mature in January-February. T. ciliata is reported to bear ripe fruits almost throughout the year.

Other botanical information

There used to be much confusion about the distinction of the genera Cedrela (from the New World) and Toona (from the Old World). Cedrela differs from Toona because of the presence of a prominent androgynophore with petals and filaments adnate to it, a cup-like calyx, bigger and more woody fruits and seedlings having entire leaflets.

Toona species are extremely variable, especially in leaf characteristics. This has resulted in a complex taxonomy at the intraspecific level; many subspecies and varieties have been described for all Malesian species. T. calantas from the Philippines is possibly no more than a geographical variant of T. ciliata or T. sureni ; its correct taxonomic status has yet to be determined.

Ecology

The various species of surian occur from sea-level up to 3000 m altitude, in South-East Asia up to 2000 m. The trees occur scattered in primary forest, but they are usually more numerous in secondary forest. They are generally found on deep, rich, moist, loamy soils with good drainage, the majority of the species preferring alkaline soils.

T. ciliata thrives in regions with annual rainfall as high as 4000 mm, while it is found naturally in areas with annual rainfall of 800-1800 mm. It prefers well-drained, deep, fertile soils, but it avoids both wet, compacted soils and poor sandy soils. T. sureni demands fertile and moist soils.

Propagation and planting

For South-East Asia the following seed counts per kg are reported: for T. calantas 83 000-420 000, for T. ciliata 280 000-425 000, for T. sinensis 403 000-721 000, and for T. sureni 64 000-468 000. In India, seed counts are most variable and seeds appear to be slightly heavier. Fruits should be collected when they start to open. They are left to dry in the sun for several days and, after shelling, seed may be separated by winnowing. Fresh seed of T. ciliata shows 60-90% germination in 8-12 days; about 80% of seed of T. sinensis stored for two months germinates, but about 45% of seed of T. sureni stored for three months germinates. Seed usually retains its viability for only 2-3 months (3-6 months for T. calantas in the Philippines), but cool storage can increase this period; seed of T. ciliata kept in sealed tins at 4-5C remained viable for one year. In the Philippines, there is 100% germination of fresh seed of T. calantas , but when stored for one month germination was 85% and when stored for two months 47%; when stored at 10-15C, germination was still 51% after 16 months. Seed can be sown without any pretreatment in beds protected from direct sunlight and rain and covered thinly with fine sand. Two to four weeks after germination the 5-10 cm tall seedlings may be transplanted. Direct seeding is uncommon, as seed may easily be washed away.

Striplings of at least 1 m tall, short stumps (7 cm shoot and 25 cm root), bare-rooted seedlings or seedlings with soil clump may be used for planting. Stumps of 1.5-2.5 cm diameter performed better than those with a diameter of 0.5-1.25 cm. For enrichment line planting of depleted primary forest or poor secondary stands, 1.5-2-year old stumps are used. A 60% rooting was obtained using stem cuttings from 2-4-year-old material of T. sureni treated with indolebutyric acid (IBA) and placed in a sawdust medium. Branch cuttings taken from old T. calantas trees and planted in nursery beds failed to sprout. Both T. sinensis and T. ciliata produce root suckers abundantly and they both coppice fairly well.

Spacings most commonly reported are 2 m × 2 m for T. ciliata and 1.5 m × 1.5 m for T. sureni . In Africa, 4-6 m × 4-6 m is used for T. ciliata and in Costa Rica 2-2.5 m × 2-2.5 m. In Hawaii, a spacing trial conducted for T. ciliata resulted in the recommended spacing of 2.7 m × 2.7 m. T. sinensis may be spaced more closely than the other Toona species as the trees develop only small and open crowns.

Because of the danger of Hypsipyla robusta attack, it is not recommended to establish pure plantations of surian.

Silviculture and management

Natural regeneration of T. sinensis is abundant, especially on the sides of ravines where moisture is readily available. Natural regeneration of T. ciliata may be abundant in well drained locations free from weed competition, although the very small seeds may be washed away and the young seedlings beaten down by rain. Natural regeneration may be profuse, even in areas outside its natural range.

In the first year weeding is important in plantations of T. ciliata . Young surian trees tolerate light shade, but later they need full overhead light and enough crown space. Trees develop best when there is lateral shade. Young plants are susceptible to browsing by game and livestock. Surian is sensitive to fire.

Recommended rotations for surian range from 40-50 years. After 40 years the growth of T. ciliata in plantations in Africa is seriously declining. T. ciliata trees planted on former skid roads in Hawaii showed significantly reduced growth and a lower survival after only 8 years.

In West Java, surian is being grown in plantations of Paraserianthes falcataria (L.) Nielsen to control stem-borer attacks. Results are promising.

In a plantation of surian, leaves can be harvested as a vegetable and fodder after 6 months. After 1 year a second thinning is recommended which yields another harvest of fodder. Subsequent thinnings can be used for the production of poles. After the fifth year, bark and fruit can be utilized for the production of aromatic oil.

Diseases and pests

T. ciliata is attacked by some fungi, the most important of which are: Ganoderma lucidum causing root and butt rot, which may be lethal, Phellinus spp. causing white rot of fallen timber or gaining access through wounds exposing dead sapwood and Trametes straminea (white stringy rot) usually saprophytic but also a wound parasite causing trunk rot.

The most serious pest is the shoot borer Hypsipyla robusta , which is a pest of most Meliaceae . Maindamage is caused by the larvae, which destroy the succulent terminal shoots by boring into the tip and tunnelling in the juvenile stem of saplings and seedlings. Resprouting of the plants, followed by repeated attacks of the insect, generally results in the development of numerous side branches and consequently in badly formed trees with multiple leaders, unsuitable for timber production. Hypsipyla robusta may also cause considerable losses of surian seed.

There is some evidence that Hypsipyla attack is reduced by planting under shade, possibly because of suppression of lateral shoots which provide the best conditions for its multiplication or because predators are more active under shaded conditions. T. ciliata can be planted in pure plantations in Latin America, as it is not attacked by the native Hypsipyla grandella . When Cedrela odorata L., which is highly susceptible to this shoot borer, is grafted on T. ciliata it becomes resistant. Differences in susceptibility of T. ciliata are recorded in Australia. The presence of a toxic compound in T. ciliata is promising for the breeding of Hypsipyla resistant Meliaceae .

Yield

Plantations of T. ciliata are reported to have a mean annual increment of 7-18 m³/ha. A saw log volume of 395 m³/ha has been estimated in a 43-year-old trial plantation in Hawaii.

Handling after harvest

Fresh logs should be removed immediately from the felling site, as they may readily be attacked by borers and termites.

Genetic resources

T. calantas is disappearing rapidly from the Philippine forests, where it is reported to be a vanishing timber tree, just like T. sureni . Hence, there is an urgent need for the conservation of both species in the Philippines. Elsewhere, stands of surian are also threatened locally because the trees are largely selectively harvested for their valuable timber.

Breeding

T. ciliata is known to have intraspecific chromosome races based on aneuploidy. There may be a correlation between rate of growth, form and wood quality, and ploidy level, and intensified selection and breeding programmes for this species may result in superior trees for timber plantations. A breeding programme for T. ciliata started in Malawi in the late 1960s.

Prospects

Surian species provide good-quality timber which can be used for various purposes. Moreover they grow fast and are easy to propagate vegetatively. Surian species, therefore, are worth including in silvicultural trials. They may also have great potential for use in mixed timber plantations to suppress pests of other timber species. The widespread planting of surian for multipurpose uses should be encouraged.

Literature

Bahadur, K.N., 1988. Monograph on the genus Toona (Meliaceae). Bishen Sing Mahendra Pal Singh, Dehra Dun. 251 pp.
Edmonds, J.M., 1993. The potential value of Toona species (Meliaceae) as multipurpose and plantation trees in Southeast Asia. Commonwealth Forestry Review 72(3): 181-186.
Grijpma, P., 1976. Resistance of Meliaceae against the shoot borer Hypsipyla with particular reference to Toona ciliata M.J. Roem. var. australis (F. v. Muell.) C.DC. In: Burley, J. & Styles, B.T. (Editors): Tropical trees. Variation, breeding and conservation. Linnean Society Symposium Series No 2. Academic Press, London. pp. 69-78.
Japing, H.W. & Oey Djoeng Seng, 1936. Cultuurproeven met wildhoutsoorten in Gadoengan - met overzicht van de literatuur betreffende deze soorten [Trial plantations of non-teak wood species in Gadungan, East Java - with survey of literature about these species]. Korte mededeelingen van het Boschbouwproefstation No 55, part I-VI. pp. 246-252.
Keating, W.G. & Bolza, E., 1982. Characteristics, properties and uses of timbers. Vol. 1: South-east Asia, Northern Australia and the Pacific. Division of Chemical Technology, Commonwealth Scientific and Industrial Research Organization. Inkata Press, Melbourne, Sydney and London. pp. 343-345.
Lamprecht, H., 1989. Silviculture in the tropics. Tropical forest ecosystems and their tree species, possibilities and methods for their long-term utilization. GTZ, Eschborn, Germany. 296 pp.
Martawijaya, A., Kartasujana, I., Mandang, Y.I., Prawira, S.A. & Kadir, K., 1992. Indonesian wood atlas. Vol. 2. Forest Products Research and Development Centre, Bogor. pp. 127-131.
Midon, M.S., 1985. Malaysian timbers - surian. Malaysian Forest Service Trade Leaflet No 93. Malaysian Timber Industry Board, Kuala Lumpur. 5 pp.
Merrifield, L.E. & Howcroft, N.H.S., 1975. Propagation of cedar, Toona sureni (Bl.) Merr., from cuttings treated with growth substances. Turrialba 25(1): 54-57.
Yao, C.E., 1987. Kalantas: a vanishing luxury lumber. Canopy International 13(6): pp. 1-2, 10.