Pouteria (PROSEA)

Plant Resources of South-East Asia
Introduction

Protologue: Hist. pl. Guiane 1: 85 (1775).

Family: Sapotaceae

Chromosome number: x= unknown; P. obovata: 2n= 26

Trade groups

Nyatoh: lightweight to medium-heavy hardwood, e.g. Pouteria duclitan (Blanco) Baehni, P. firma (Miq.) Baehni, P. linggensis (Burck) Baehni, P. malaccensis (C.B. Clarke) Baehni, P. obovata (R.Br.) Baehni (partly).

Bitis: heavy hardwood, e.g. P. obovata (partly).

Vernacular names

Nyatoh

padang (En)
Indonesia: nyatuh
Papua New Guinea: pencil cedar, planchonella, silk wood
Philippines: white nato
Burma: thitcho.

Bitis

Malaysia: nyatoh batu (Sabah, Sarawak).

Origin and geographic distribution

The very large genus Pouteria consists of about 320 species and occurs in tropical Asia, the Pacific and South America. Two main centres of diversity may be distinguished, the first being New Guinea, Australia and New Caledonia (the former genus Planchonella), the second South America (Pouteria s.s.). About 50 species occur in Malesia. New Guinea and New Caledonia are very rich in species, each accommodating about 40 species, most of which are endemic. Among the most widespread species are P. duclitan, P. firma, P. linggensis and P. obovata, covering whole Malesia or even more.

Uses

The timber is usually marketed together with the timber of other Sapotaceae genera as "nyatoh". Nyatoh is a general-purpose timber, which is however only moderately durable and therefore particularly suitable for indoor use. It is in demand for fine furniture, decorative doors and panelling. It is also used for interior finishing, joinery and flooring. Locally, nyatoh timber is used for house-building, e.g. in Indonesia. The wood of some species is used for inlaying and carving, and for musical instruments, cabinet work, picture frames and fan ribs, e.g. in the Philippines. Nyatoh can also be used in the production of plywood as it makes good-quality veneer.

Bitis, being heavier and more durable, is used for heavy constructional work, heavy-duty flooring, posts, window and door frames, paving blocks, implements and turnery.

Some species have edible fruits, e.g. P. campechiana (Kunth) Baehni (canistel), P. sapota (Jacq.) H.E. Moore & Stearn (sapote), and P. maclayana , others are used in traditional medicine, e.g. P. obovata. A decoction of the leaves of the latter species is used against stomachache, crushed leaves are used as a poultice in cases of lumbago, and heated bark of P. obovata and P. firma may be chewed against sprue, sometimes together with betel.

The latex is rarely used; in New Guinea the very sticky latex of some species is said to be used as birdlime.

Production and international trade

Usually Pouteria timber is available only in limited quantities, and in many areas it is much less important than the timber from Palaquium, Payena and Madhuca species, e.g. in Peninsular Malaysia, Borneo and the Philippines. Most of the "white planchonella" timber, which is imported in constant but not large quantities in Japan, originates from New Guinea and the Solomon Islands. Much of the timber from Pouteria species is mixed with that of other Sapotaceae genera and traded collectively as nyatoh or occasionally bitis. The export of nyatoh sawn timber from Peninsular Malaysia decreased from 16 500 m³ (with a value of US$ 2.1 million) in 1981 to 9500 m³ (with a value of US$ 1.3 million) in 1986. By 1990 the export had increased to 32 500 m³ (with a value of US$ 6.1 million), but in 1992 it was only 8000 m³ with a value of US$ 2.8 million. Large amounts of nyatoh are also exported from Sarawak and Sabah; the export of round logs from Sabah was 65 000 m³ (worth US$ 6.3 million) in 1987, and in 1992 the export of logs was 14 000 m³ and of sawn timber 8500 m³ with a total value of US$ 4.4 million. In Papua New Guinea nyatoh is ranked in MEP (Minimum Export Price) group 1, and fetched a minimum export price of US$ 100/m³ for saw logs in 1992. Nyatoh timber is often exported to Europe as planks of up to 425 cm × 30 cm × 7 cm.

Properties

The properties of Pouteria timber may differ considerably, e.g. in density which varies between different species from 360 to 1220 kg/m³ at 15% moisture content. This is not really surprising for such a large genus. The timber can be classified among the light to heavy nyatoh timbers and occasionally (P. obovata) as bitis timber.

A general description of nyatoh and bitis is given here. These timber groups are not well demarcated, and include Pouteria, Palaquium, Madhuca, Payena and occasionally some other Sapotaceae genera. The arbitrary limit lies at a density of 850 kg/m³.

Nyatoh is a light to medium-weight, moderately hard to hard red meranti-like wood. The heartwood is pinkish-brown to reddish-brown and only moderately distinct from the lighter sapwood. The density is (420-)550-800(-850) kg/m³ at 15% moisture content; that of the majority of the commercial supply 600-700 kg/m³. The grain is shallowly interlocked, texture moderately fine and even.

At 15% moisture content the modulus of rupture is 70-130 N/mm², modulus of elasticity 10 000-18 000 N/mm², compression parallel to grain 28-54 N/mm², compression perpendicular to grain 2.5-7 N/mm², shear 8.5-11(-17) N/mm², cleavage 39-77 N/mm radial and 49-87 N/mm tangential, Janka side hardness 3700-7000 N and Janka end hardness 3900-7600 N.

The recorded rates of shrinkage of nyatoh are moderate, from green to 15% moisture content 1.3-3% radial and 2.3-4% tangential, from green to oven dry about 4.1% radial and 7.6% tangential. Air drying of 40 mm thick boards takes approximately 4 months, 25 mm thick boards about 2 months. The timber can be satisfactorily dried by using kiln schedule E (Malaysia). Form stability is medium to good when dry. Pouteria timber from the Philippines (white nato) seasons fairly well, but rapid drying is needed to avoid sap staining and blueing. White nato wood may shrink considerably. Kiln drying of boards of 2.5 cm thick of Pouteria timber from Papua New Guinea takes 4-4.5 days under favourable conditions. These boards may shrink up to 7% in width and 8.5% in thickness when dried to 10% moisture content.

The sawing properties are variable, probably depending on the species, but there may also be great variation within a species. Some nyatoh-producing species contain silica, which makes the timber difficult to work. There may be gum accumulation on cutters. Nyatoh is easy to polish when the grain is properly filled. The wood is easy to turn. Pre-boring for nails and screws is advised because of easy splitting. There are no problems with gluing. The fine grain and colour make it suitable for veneer; it can be peeled at a 91° peeling angle without pretreatment. Sometimes the wood is figured and then the veneer can be very attractive, especially when radially sliced. Peeling is reported as easy to fairly difficult, and a good plywood can be made from the timber.

Nyatoh is rated as only moderately durable. Graveyard tests in Indonesia with wood of P. duclitan and P. obovoidea showed a service life in contact with the ground of 1.2-1.4 years only. Nyatoh is prone to termite attack and susceptible to fungal attack, but not to powder-post beetles. Treated nyatoh timber can be very durable. However, the heartwood is very resistant to preservative treatment. The sapwood is less difficult to impregnate. Small wood samples from P. doonsaf may be impregnated completely using a 4% solution of natrium fluoride; the impregnation with copper aphtenate and a mixture of creosote and diesel is less successful.

Bitis comprises heavier timber, with a density of 850-1150 kg/m³ at 15% moisture content. The heartwood is reddish-brown to dark brown, and clearly differentiated form the lighter sapwood. The grain is fairly straight, texture moderately fine and even. Bitis is very hard and strong, and much more durable than nyatoh.

At 15% moisture content the modulus of rupture is 105-170 N/mm², modulus of elasticity 10 000-23 800 N/mm², compression parallel to grain 65-90 N/mm², compression perpendicular to grain 9-12.5 N/mm², shear 10-17 N/mm², cleavage c. 86 N/mm radial and 67 N/mm tangential, and Janka side hardness 14 400-14 900 N.

Bitis is difficult to dry; shrinkage rates are high (from green to 15% moisture content 3.0% radial and 4.0% tangential), and there is a tendency to surface checking. A mild kiln schedule (B in Malaysia) should be used.

Bitis is difficult to work, rapidly blunting saws and cutters due to the presence of silica, but it produces a smooth surface in planing and takes stain and polish satisfactorily. The timber tends to split in boring and mortising. Bitis is not suitable for veneer and plywood because it is difficult to peel.

Bitis timber is rated as durable and is resistant to termite attack. It is very difficult to impregnate.

Freshly felled wood often has a sour smell and bitter taste. It lathers freely when rubbed with water. The dust from sawn timber may cause irritation to skin and mucous membranes.

Description

Shrubs to large trees, with latex, up to 50 m tall, with generally columnar, buttressed bole (but buttresses sometimes absent or bole fluted or twisted), up to 100(-150) cm in diameter; outer bark smooth, shallowly cracked or fissured, usually brown, inner bark soft and fibrous or granular, yellowish, red or reddish-brown; twigs usually slender and terete, at first hairy but glabrescent.
Leaves arranged spirally, generally loosely to densely clustered at ends of upturning twigs, simple and entire, obtuse to acuminate, usually glabrous above and glabrous to densely hairy beneath; secondary veins usually diminishing until inconspicuous at the leaf margin, tertiary veins transverse to secondary veins, parallel to secondary veins or reticulate; petiole usually of even thickness throughout its length; stipules absent or minute and early caducous.
Inflorescence small, axillary or sometimes on a short leafless shoot, 1-many-flowered.
Flowers usually bisexual, sometimes unisexual; sepals (4-)5(-6), united at base and arranged spirally, with imbricate lobes; corolla (4-)5(-8)-lobed, usually glabrous, white, pale yellow or whitish-green, rarely pink or red; stamens (4-)5(-8), inserted at the throat of the corolla tube opposite corolla lobes, alternating with staminodes inserted between corolla lobes; pistil 1, with globose or ovoid (4-)5(-6)-celled ovary and rather short style.
Fruit a berry with persistent sepals and style and fleshy pericarp, 1-6-seeded.
Seed with a thin to rather thick glossy testa and narrow to broad, linear to broadly oblong hilum; endosperm absent to abundant, cotyledons thick or thin.
Seedling with epigeal germination, with strongly developed taproot; first pair of leaves opposite or subopposite, subsequent leaves spiral and soon similar to leaves of adult trees.

Wood anatomy

Macroscopic characters

Heartwood light red-brown to yellow-brown, indistinctly demarcated from the sapwood.
Grain straight.
Texture fine to moderately fine.
Growth rings indistinct to barely visible to the naked eye; vessels in a typically radial arrangement which gives the end surface a radially perforated appearance, visible to the naked eye; parenchyma and rays not distinct without a lens.

Microscopic characters

Growth rings faint or absent, if present marked by difference in spacing of tangential parenchyma bands, and in fibre wall thickness on either side of the ring boundary.
Vessels diffuse, 12-18/mm², mainly in radial multiples of 2-5(-9), in more or less continuous radial to somewhat oblique rows, round to oval, average tangential diameter 50-110 μm; perforations simple; intervessel pits alternate, round to polygonal, (5-)6-8 μm; vessel-ray pits mainly confined to the upright and square cells, mostly large and simple, horizontally to vertically elongate or round, partly half-bordered, scarce in procumbent cells; helical thickenings absent; gum-like deposits absent.
Fibres generally 1000-2000 μm long, some fibres septate, mostly medium thick-walled, with simple to minutely bordered pits mainly confined to the radial walls.
Parenchyma abundant, diffuse, diffuse-in-aggregates or in fine discontinuous to continuous 1-2-seriate, irregular wavy band sometimes forming a reticulate pattern, 5-8 lines per radial mm, in 3-8-celled strands.
Rays 11-17/mm, 1-3(-4)-seriate, multiseriates usually with uniseriate tails, up to 800 μm high, heterocellular with 1-4 rows of upright and square marginal cells and procumbent body cells.
Crystals and silica bodies sometimes present (although not in the species studied).

Species studied: P. firma, P. macrantha, P. malaccensis, P. obovata.

Growth and development

The trees flower fairly frequently in comparison with dipterocarps, and there is a tendency for many individuals in a certain area to flower simultaneously. Fruits may ripen in about 7 months after flowering. They are eaten by mammals such as monkeys, squirrels and bats, which scatter the seeds. Probably some birds eat the fruits as well.

Other botanical information

Pouteria as dealt with here, includes Planchonella. In most of the literature, Planchonella is considered to represent a separate genus, having thin cotyledons and thick endosperm, whereas Pouteria has thick cotyledons and thin or lacking endosperm. Moreover, the hilum in Planchonella is usually narrow and linear, in Pouteria it is usually broad; the fruits in Pouteria are often large and fleshy, in Planchonella generally smaller. Planchonella has an Asiatic main centre of distribution, whereas Pouteria in the narrow sense has its main centre of distribution in South America. However, the above-mentioned characters show overlap between the two genera, as do the areas of distribution, which seems to be ample reason for not keeping Planchonella apart from Pouteria.

Many species now included in Pouteria were formerly placed in Sideroxylon. In accordance with modern genus delimitations, Sideroxylon is principally a genus from South America and Africa (and the surrounding islands), and differs from Pouteria in its small and more or less basal hilum.

In Australia some species supply good timber, e.g. Pouteria pohlmaniana (F. v. Mueller) Baehni and P. sericea (Aiton) Baehni. The timber of P. vitiensis (Gillespie) Degener is used in the Fiji Islands.

Ecology

Like many other Sapotaceae, Pouteria trees occur particularly in primary forest, rarely in secondary forest, most commonly in the lowland, but some species can be found in montane forest. In New Guinea some species may reach 2500 m altitude. They belong to the middle or uppermost storey of the forest but are not emergents. The different species can grow on a variety of soils, ranging from sandy to clayey, and sometimes on young volcanic soils (e.g. P. macrantha in Sulawesi). Some species are commonly found in swamp forest (e.g. P. malaccensis), sometimes even in peat swamps (e.g. P. maingayi). Others occur on rocky coasts (e.g. P. linggensis) or on limestone (e.g. P. luzoniensis). P. obovata is ecologically the most versatile species, occurring on rocky and sandy sea coasts, on the landward side of mangroves, on limestone hills and in both primary and secondary forest.

Several species are locally common, but they usually occur scattered in the forest, e.g. P. duclitan in Java, P. maingayi and P. malaccensis in Peninsular Malaysia, P. macrantha in the Philippines and P. luzoniensis in Papua New Guinea.

Propagation and planting

The seeds are fairly large to large (about 1-4 cm long) and may germinate rapidly (4-6 weeks after shedding) or more slowly (10-26 weeks after shedding, e.g. P. maingayi).

Silviculture and management

Natural regeneration is often scarce in logged-over forest and trees are very slow to colonize secondary forest. Sometimes natural regeneration in logged-over forest is plentiful, e.g. P. moluccana in South Sulawesi (Indonesia).

Diseases and pests

Living nyatoh trees are reportedly attacked by longhorn beetles in Peninsular Malaysia, the larvae damaging the timber at the base of the trunk by boring long tunnels, and by fungi in Indonesia. Although it is unknown to which genera and species this information refers, Pouteria species might also be susceptible to beetle and fungal attack.

Genetic resources

Just like other Sapotaceae producing timber, Pouteria species might be liable to genetic erosion as they occur particularly in undisturbed forest and usually grow scattered in the forest.

Prospects

Nyatoh is a silviculturally neglected timber which can be valuable for indoor uses. It is in demand for furniture and plywood. The wood of P. malaccensis from Peninsular Malaysia is very suitable for plywood, especially in relation to gluing, which gives good results when using phenol-resorcinol formaldehyde. Promising results were obtained by using mixed-species veneer of P. malaccensis and other wood and urea formaldehyde glue. Pouteria timber has been tested only rarely, and the identity of the species tested was often doubtful or unknown. Wood property tests on properly identified logs are desirable.

Literature

Backer, C.A. & Bakhuizen van den Brink, R.C., 1965. Flora of Java. Vol. 2. Noordhoff, Groningen. pp. 189-190.
Burgess, P.F., 1966. Timbers of Sabah. Sabah Forest Records No 6. Forest Department, Sabah, Sandakan. pp. 447-455.
Forestry and Forest Products Research Institute, 1974. The properties of tropical woods 20. Studies on the utilization of nine species from New Guinea and other areas. Bulletin of the Forestry and Forest Products Research Institute, Tokyo No 269: 1-95.
Herrmann-Erlee, M.P.M. & van Royen, P., 1957. Revision of the Sapotaceae of the Malaysian area in a wider sense 9. Pouteria Aublet. Blumea 8: 452-509.
Heyne, K., 1927. De nuttige planten van Nederlandsch Indië [The useful plants of the Dutch East Indies]. 2nd edition. Vol. 2. Departement van Landbouw, Nijverheid en Handel in Nederlandsch-Indië, 's-Gravenhage. pp. 1244-1245.
Meniado, J.A., 1980. About the wood nato. Forpride Digest 9(1): 19-34.
Meniado, J.A., Tamolang, F.N., Lopez, F.R., America, W.M. & Alonzo, D.S., 1975. Wood identification handbook for Philippine timbers. Vol. 1. Government Printing Office, Manila. pp. 322-326.
Mohd Hamami Sahri, Jalaluddin Harun, Mohd Zin Jusoh & Pan, K.A., 1986. The glue joint strength of four under-utilized Malaysian hardwood species. Malaysian Forester 49: 79-91.
Ng, F.S.P., 1972. Sapotaceae. In: Whitmore, T.C. (Editor): Tree flora of Malaya. A manual for foresters. Vol. 1. Longman Malaysia SDN Berhad, Kuala Lumpur. pp. 388-439.
van Royen, P., 1957. Revision of the Sapotaceae of the Malaysian area in a wider sense 7. Planchonella Pierre. Blumea 8: 235-445.

Selection of species

Authors

R.H.M.J. Lemmens (general part, properties, selection of species),
B. Louman (general part),
R. Klaassen (wood anatomy)