Pinus (PROSEA Timbers)

Plant Resources of South-East Asia
Introduction

List of species

Pinus L.

Protologue: Sp. pl. 2: 1000 (1753)

Family: Pinaceae

Chromosome number: x= 12; 2n= 24 (for the vast majority of species)

Trade groups

Pine: medium-weight timber, e.g. Pinus kesiya Royle ex Gordon, P. merkusii Junghuhn & de Vriese.

Vernacular names

Pine

pitch pine, deal (En)
Pin (Fr)
Indonesia: tusam
Malaysia: pokok pine
Burma: tinyu tinshu
Cambodia: sral
Thailand: son-sambai, son-songbai, sonkhao (central)
Vietnam: thông.

Origin and geographic distribution

The genus consists of slightly more than 100 species. The evolutionary origin of the genus has been located in the early Jurassic or late Triassic period. The earliest fossil records are all from eastern Siberia. The present-day centres of diversity are located in Mexico, the eastern United States, and the mainland of eastern Asia. Only 2 species occur naturally in the Malesian region, while 3 others are planted locally.

Uses

Pine is a good general-purpose timber, although in woodworking and finishing aspects its resinous nature requires special attention. The wood of species grown in Malesia is moderately hard to hard, but the heartwood is not very durable. It can be put to a great number of uses such as both light and heavy constructional work, joinery (window frames, doors, weatherboarding, etc.), boxes and crates, posts and poles, pencils and furniture. It may be used for flooring in rooms subject to light pedestrian traffic, and for ship and boat building. It is recommended for treated sleepers and for blockboard manufacturing. It makes an acceptable quality of veneer and plywood. The suitability of the wood of individual species for the different specific end-uses is mainly determined by its density and resinous nature. The wood of Caribbean pine (P. caribaea) is usually less heavy and it also exudes much resin, which makes it less suitable for certain uses e.g. joinery and flooring.

Pine wood is used for making particle board. Benguet pine (P. kesiya) in particular yields high-quality board. The pine species grown in the Malesian region are usually of an inferior quality with regard to their pulping characteristics. In general, they have comparatively thick tracheid walls which makes paper less flexible, but the addition of small amounts of this pulp to pulp of other wood leads to a higher tear strength.

When tapped, pine yields an oleoresin which is distilled to give turpentine and rosin which is used in e.g. paint and batik industries. Large-scale production takes place in several localities within Malesia.

Pine-leaf oil is sometimes used for medicinal baths, and the seeds may be consumed locally.

Several pine species have been tested for their usefulness in shading out alang-alang (Imperata cylindrica (L.). Raeuschel) with fairly good results.

Production and international trade

Pine is important for the production of timber, pulp and turpentine. No figures on trade and export are available, partly because the timber is often used locally, and the pulp is often mixed with pulp of other woods. The total production of turpentine in Indonesia was about 5.3 million t in 1989. The export value of gum turpentine increased from US$ 113 500 in 1983 to US$ 790 000 in 1987.

Properties

Pine is a medium-weight, moderately hard wood. The colour of the heartwood is yellowish-brown to red-brown, depending on the resin content (more resin yields darker wood). The sapwood is yellowish-white to light reddish-yellow, and sharply defined from the heartwood. The density of heartwood of P. merkusii from Sumatra is 565-750 kg/m³ at 15% moisture content. The density of timber of the same species grown in Burma and Indo-China is normally less: 480-530 kg/m³. Timber of P. kesiya from the Philippines and Burma has an average density of 560 kg/m³ at 12% moisture content, and plantation-grown Caribbean pine (P. caribaea) 410 kg/m³. The grain of pine wood is even to finely interlocked, texture coarse.

At 15% moisture content the modulus of rupture is 41-83 N/mm², modulus of elasticity 4600-12 500 N/mm² (up to 15 500 N/mm²at 12% moisture content in P. kesiya wood from the Philippines), compression parallel to grain 24-44 N/mm², shear 8-10 N/mm² (in P. caribaea usually slightly less), cleavage 38-42 N/mm radially and 46-55 N/mm tangentially, and Janka side hardness 2760-3800 N (slightly less in P. caribaea).

The rates of shrinkage of pine are medium, 3.9-4.9% radial and 6.4-8.3% tangential from green to oven dry. Seasoning properties of P. merkusii timber are good and no serious difficulties are encountered, provided stock is converted soon after felling and protected during drying. Kiln-drying properties are rated as good, but resin and staining may cause problems. High-temperature drying (at 115° C) takes 24 hours for boards 2.5 cm thick and 48 hours for boards 5 cm thick; no serious defects develop. The wood of P. kesiya seasons well without serious degrade when the timber is well piled and closely stacked. Kiln drying is easy, but it is advised to use a mild schedule; fast drying at high temperature may result in serious splitting and excessive resin exudation. For wood of P. merkusii in Indonesia, a drying temperature of 54-82° C and a corresponding relative humidity of 76% to 30% is recommended. Plantation-grown material of P. caribaea from Fiji seasons satisfactorily provided it is under cover, well stacked with closely spaced stickers, and weighted to prevent distortion. Boards of 30 mm thick require about 6 weeks for air drying from green to 20% moisture content. Conventional kiln drying is successful for both 25 mm thick material (which takes 3-4 days to dry to 12-14% moisture content) and 50 mm thick material. High temperature drying has proved successful for framing sizes. Boards of 30 mm thick timber of plantation-grown P. caribaea may be dried in a solar kiln from 145% to 12% moisture content in 40 days.

The green wood is normally easily worked both by hand and machine, although light damage may occur due to the presence of resin. Sawing very resinous material is usually classified as difficult. This can be cured by spraying the sawteeth with paraffin. The timber works easily when air-dried, but it is liable to produce a rough finish. It nails, tongues and grooves in a perfect fashion, and generally glues and takes paint and varnish without difficulty. To glue resinous material the surfaces must be freshly planed or sanded, and then treated with a cleaning fluid (e.g. white spirit). Resinous wood is sometimes difficult to paint and varnish properly because the resin may exude again under the coating layer. The timber of P. kesiya is easy to cut into smooth, tight veneer of uniform thickness at a cutting temperature of 50-70° C. During drying the veneer shows slight to moderate shrinkage and warping, and is usually split-free. To obtain an acceptable quality of veneer it is often necessary to patch or fill imperfections in the wood due to the presence of knots and localized raised grain, and then to sand the surface.

Pine timber is only moderately durable, and often prone to termite attack. It is also susceptible to blue stain, ambrosia beetles and dry-wood borers. Graveyeard tests on P. merkusii in Indonesia showed a service life in contact with the ground of 1-4.5 years. Heartwood of P. merkusii can be impregnated with CCA preservative quite well; it is classified as "permeable". Heartwood of P. caribaea is rated as moderately resistant to impregnation.

Pines give a long-fibred pulpwood. The wood is suitable for making wood-wool boards.

Wood of P. merkusii contains 55% cellulose, 24% lignin, 14% pentosan, 1.1.% ash and 0.2% silica. The solubility is 6.3% in alcohol-benzene, 0.4% in cold water, 3.2% in hot water and 11.1% in a 1% NaOH solution. The energy value of the wood is 20 300-23 200 kJ/kg.

The oleoresin is a pale yellow, clear and sticky mass, which becomes brittle on evaporation. It is a hydrophobic substance soluble in neutral, non-polar organic solvents such as dry ethyl ether, hexane, and other petroleum solvents, and it mainly consists of terpenoids, hydrocarbons, and neutral compounds. On distillation it produces gum rosin and gum turpentine in a ratio of 4-6 : 1. Pine bark contains tannin; from the bark of P. caribaea , for instance, about 10% tannin can be extracted; it can be dried to a reddish powder soluble in water. Ethyl alcohol extracts of P. merkusii showed anti-cancer activity in tests in the Philippines.

Description

Usually medium-sized, monoecious evergreen trees of 15-35(-45) m tall, usually with a straight bole which in dense stands is free of branches for 10-25 m and has a diameter of up to 100(-140) cm; bole non-buttressed but distinctly broadened at base in solitary trees; bark usually thick, rough and deeply furrowed though variable, sometimes even within the same species; branches disposed in regular whorls, branchlets glabrous, with a leafless base.
Leaves in mature trees of two kinds: scale leaves which are triangular-lanceolate, early deciduous, bearing in their axils the short shoots, and needle-like leaves, in clusters of 2-4(-5) (depending on the species), the latter persistent for two or more years, either semi-circular or triangular in cross-section and the margin often minutely toothed.
Male strobili cylindrical, produced in clusters around the base of the young shoot, yellow or reddish, consisting of numerous, spirally arranged scales, each with 2 inverted pollen sacs.
Female cones usually terminal or sub-terminal, very variable in outline, consisting of spirally arranged scales which are thickened at the apex (called the apophysis), and which bear a stout prickle, mucro or hook (the umbo); each scale bearing 2 ovules.
Seed often egg-shaped with a coat of varying hardness, usually having a large papery wing.
Seedling with hypogeal germination; cotyledons plumose; the primary leaves (scale leaves) appearing within a few weeks and secondary leaves (needle-like leaves) usually appearing during the second year; root system consisting of a taproot with fine roots near the soil surface and near the root tip.

Wood anatomy

Macroscopic characters

Sapwood merging into heartwood except in old trees; sapwood whitish or creamy white, heartwood yellow or yellowish-red to orange-brown.
Grain straight to uneven.
Texture coarse.
Darker streaks present due to latewood bands and darker lines like scratches seen on longitudinal surfaces due to axial resin canals.
Growth rings distinct but irregular in width, wood resinous; rays very fine, indistinct to the naked eye.

Microscopic characters

Growth rings distinct with prominent latewood bands.
Tracheids coarse, arranged in prominent radial rows 35-45 μm wide in the latewood, squarish rectangular to hexagonal in the earlywood, tracheids less aligned in the earlywood, cell wall thickness 3-5 μm, transition from earlywood to latewood fairly abrupt; tracheids 3-10 mm (average 7 mm) long; inter-tracheid pits opposite in 1-2 rows, prominent on radial walls of the earlywood cells; pits absent from tangential walls of last few latewood tracheids.
Axial resin canals irregularly distributed but mostly in the middle or outer portion of the growth ring, with thin-walled epithelial cells; canal diameter 170-190 μm; horizontal resin canals in rays with thin-walled epithelial cells 45-55 μm in diameter.
Parenchyma absent.
Rays 4-7/mm, very fine; uniseriate and fusiform rays present, approximately 10-15 cells high, ray tracheids present with one to several marginal cells occasionally interspersed, dentate; crossfield pitting single large window-like in the earlywood.

Species studied: P. kesiya, P. merkusii.

Distinguishing characteristics: P. merkusii is typically a hard pine anatomically; the wood is more dense, the transition from earlywood to latewood more abrupt and vertical resin ducts are larger than in P. kesiya.

Growth and development

Young trees of mainland provenances of P. merkusii pass from 3-5 years through a so-called "grass stage" characterized by densely clustered needles and short shoots and minimal height growth. However, Sumatran provenances of the same species have no "grass stage" and they grow quickly upwards. This improves their chances in the competition with weeds which grow vigorously in the moist climate. Mycorrhizae are required for successful growth and allow seedlings to survive in more adverse sites. The normal architecture of pines is Rauh's model. The trunk is monopodial and grows rhythmically, and develops tiers of branches; the formation of cones does not affect shoot construction. Sometimes "foxtails" occur, plants without branching and without growth rings in the wood, e.g. in P. caribaea and P. merkusii. Foxtailing is a reaction to off-site planting. Locally, e.g. in East Kalimantan, 40-50% foxtailing has been recorded in plantations of P. caribaea. For P. caribaea, bole straightness generally improves from the subtropics towards the tropics.

In early stages of growth, trees of P. kesiya are prone to fire damage. P. caribaea is rated as moderately fire resistant.

In plantations, trees of P. merkusii reach sexual maturity when about 20 years old. They bear cones every year, although seed production varies. Trees of P. caribaea planted in Peninsular Malaysia and East Kalimantan and of P. oocarpa planted in East Kalimantan do not produce seed, due to unsynchronized production of male and female cones. Seeds needed to establish new plantations must be derived from elsewhere.

The annual growth rate of Benguet pine (P. kesiya) in the Philippines is 0.8-1.9 cm in diameter and 54-142 cm in height. Caribbean pine grows in the Philippines on average 2.8 cm/year in diameter and 2.7 m/year in height.

Pollination and seed dispersal is by wind. Sometimes the birds, rodents and people who gather the seeds for food, also disperse them.

Other botanical information

The genus Pinus is often divided into 2 subgenera, i.e. Haploxylon (Shaw) Mirov and Diploxylon (Shaw) Mirov, based among other things on the number of vascular bundles in the leaves (one and two, respectively). The first subgenus comprises species with soft wood, the second species with generally heavier wood. The species occurring in Malesia belong to the subgenus Diploxylon.

The most commonly planted pines (not indigenous) in South-East Asia are P. caribaea, P. oocarpa and P. patula. Some other species are much less commonly cultivated in plantations: P. elliottii Engelm. (e.g. Kalimantan), P. radiata D. Don, P. occidentalis Swartz and P. massoniana Lambert (e.g. Sabah), P. cubensis Grisebach, P. strobus L. (e.g. Sarawak), P. taeda L. (e.g. Papua New Guinea) and P. montezumae Lambert (e.g. Java).

In Sumatra three different strains of P. merkusii have been recognized (the Aceh, Tapanuli and Kerinci strains) which differ markedly in e.g. stem form, branching, bark, resin content and susceptibility to attack by the moth Milionia basalis.

Ecology

The naturally occurring pines of South-East Asia (P. kesiya and P. merkusii) inhabit a wide range of forest and savanna habitats. They are pioneers and their natural range is extended by colonization following disturbances such as fire. They grow, for instance, scattered in fire-prone grassland and woodland. The trees are increasing in number in recently disturbed areas. They are strongly light-demanding and habitually grow in pure stands. Pines grow naturally in South-East Asia only in strongly seasonal environments.

P. kesiya grows in areas with a mean annual rainfall of 700-1800 mm and a pronounced dry season. Mean annual temperature in the area of distribution is 17-22° C, mean maximum temperature of the hottest month 26-30° C, mean minimum temperature of the coldest month 10-18° C.

P. merkusii occurs in areas with mean annual rainfall of 1000-2800(-3500) mm, a mean annual temperature of 21-28° C, mean maximum temperature of the hottest month of 24-32° C, and mean minimum temperature of the coldest month 18-24° C.

The species planted in South-East Asia demand light- to medium-textured, neutral to acid soils (optimum pH 5-6) which are well-drained. They may sometimes tolerate shallow soils (P. oocarpa) or seasonally waterlogged soils (P. caribaea). P. caribaea tolerates salt winds and hence may be planted near the coast.

Propagation and planting

Successful natural regeneration is only possible where a relatively large amount of sunlight reaches the ground. In Sumatra ripe seeds are produced most abundantly between July and November, but viable seeds are produced throughout the year. Only cones that have just changed their colour from green to brown should be collected and air dried. The weight of 1000 seeds of P. caribaea is 14-19 g, of P. kesiya 16-18 g, of P. oocarpa 18-24 g, of Sumatran P. merkusii about 17 g, and of continental provenances of P. merkusii 25-33 g. The seeds can be stored for several years, provided they are kept dry, cold and in an airtight container. However, seeds of P. merkusii are reported to have a rather short viability; seeds from Sumatra can be stored dry for only 1-2 years, and those from continental Asia during even shorter periods.

Seeds germinate in 8-12(-21) days, and need no pretreatment. However, they are often soaked in cold water overnight before sowing. For P. merkusii seeds, a germination rate of 40-60% may be expected. Seedlings need ectomycorrhizae for optimal growth. Natural injection may occur locally, but a reliable method of inducing seedlings to form mycorrhizal associations is to expose them to saplings 30-80 cm tall which are already mycorrhiza carriers. The "mother trees" are planted in the nursery beds a year before sowing, at a spacing of 1 m × 1 m. Another method of obtaining mycorrhiza is to mix ordinary topsoil from pine forests with potting medium (in a ratio of 1 : 4-10), or to inoculate with vegetative mycelia, spores, mycorrhizal capsules or tablets. The latter methods will probably gain importance in the near future. The fungi used for inoculation of pines in South-East Asia include Pisolithus tinctorius, Scleroderma sp., Thelephora terrestris, Cenoccoccum graniforme and Rhizopogon sp. After about 8 months the seedlings of P. merkusii in nursery beds are 20-25 cm tall and ready for planting into the field. Seedlings of P. caribaea and P. kesiya may already be suitable for transplanting after 4-6 months. Field planting is carried out at spacings of 4 m × 4 m (for resin production) or 3 m × 1-2 m (for timber production). Experiments in Indonesia showed that scions of P. caribaea, and particularly P. oocarpa, grafted onto P. merkusii grow faster in height than controls of the stock species.

Propagation by tissue culture is possible. Suspensor, root tissue and hypocotyl segments of 2-week-old seedlings of P. merkusii have been used, and they all readily yield callus when cultured on a Murashige and Skoog mineral formulation supplemented with naphthalene acetic acid (0.25-0.65 ppm) and benzylamino purine (1.0-2.0 ppm).

In the Philippines Benguet pine is recommended as a shade tree for coffee plantations. It is planted at a spacing of 3 m × 3 m, and after 5-7 years, when the pines have reached a height of at least 4 m, young coffee is planted. Weeding is necessary for about 3 years until the canopies of the growing pine and coffee have completely overtopped the grasses. Another viable agroforestry system in the Philippines is raising goats in forest of P. kesiya at a stocking rate of 4 goats/ha. In Indonesia P. merkusii has been successfully intercropped with Irish potatoes.

Silviculture and management

In plantations of P. merkusii the first thinning is usually carried out in the 9th or 10th year, and about every 5 years thereafter. Rotation cycles of 30 years are needed for optimal timber production and have been stipulated by the Indonesian forestry administration. For the production of pulpwood, a cutting cycle of 15 years is usually practised.

Weeding operations depend on the species, site and priority. P. merkusii and P. kesiya require more weeding than P. caribaea and P. oocarpa. In Thailand weeding in P. kesiya plantations is carried out 4 times a year. The prolonged "grass stage" often present in young trees of P. merkusii means increased weeding requirements when compared to P. caribaea, P. oocarpa and P. kesiya.

The total area of natural pine forest in Thailand has been estimated at 228 000 ha. P. kesiya is the preferred species for reforestation on highland sites in Thailand. In trials in the Philippines at 350 m and 750 m altitude, P. caribaea and P. oocarpa showed better growth and/or survival rate than P. kesiya, P. merkusii, P. elliottii, P. radiata and P. patula.

P. caribaea responds well to low levels of nitrogen fertilization, but trials in the Philippines showed no response to either phosphorus or potassium.

Diseases and pests

Damping-off is the most common nursery disease, associated with P. caribaea in particular. Regular spraying with fungicides, careful monitoring of the moisture level in the nursery beds and potting media, and sterilization of the nursery medium may reduce damping-off substantially.

Pines in plantations are fairly susceptible to shoot moth and needle blight attack. In the Philippines bark beetles (Ips calligraphus) may cause problems in plantations of P. kesiya, and pine shoot moths (Dioryctria rubella) in stands of P. kesiya and P. caribaea. Pine shoot moth is effectively controlled by using the insecticides fenitrothion (0.1%) and fenvalerate (0.2%). The main pests in northern Sumatra are members of the Psychid and Geometrid families (e.g. Milionia basalis), shoot- and stem-boring Pyralids, and local squirrels. In Malaysia termites are reported as the main pest in plantations of P. caribaea.

Harvesting

Several methods of harvesting the resin are practised. The resin is found in the intercellular canals in the wood (especially sapwood) and products are often termed "naval stores" because of their historic use for ship caulking. Living pine trees are tapped (wounded), the first cut of about 1.3 cm wide and 30 cm long being made 30-40 cm from the ground, followed by a series of chippings until breast height. A sulphuric acid solution (usually 40-60%) is applied immediately after chipping. This process yields the "gum naval stores", still the major source of the worlds supply of rosin and turpentine. "Wood naval stores" can be obtained by solvent extraction of stumps of old trees; the resin obtained in this manner is less pure. Turpentine and wood resin can also be obtained as by-products from the kraft (sulphate) pulping of pines. Turpentine is removed from the chip digester during the initial steaming and condensed from the relief gases. This method gives "kraft naval stores".

Yield

On suitable sites pines can achieve a mean annual increment of up to 28(-40) m³/ha up to the 13th year. For an average site quality (4) the mean annual increment of P. merkusii is 22.4 m³/ha in a 25-year rotation, but it may reach 30 m³/ha for better site quality (6) in a 20-year rotation. In Sumatra 30-year-old stands of P. merkusii trees (with an average diameter of 58.5 cm) may have a standing volume of 397 m³/ha with a total yield of 814 m³/ha. The target volume in pine plantations in East Kalimantan is 200-300 m³/ha with a cutting cycle of up to 20 years. The yield of resin from P. merkusii is 420-750 kg/ha. Trees of P. kesiya are sometimes commercially tapped for resin prior to harvesting of the main product, which is timber. Trees in the Philippines older than 20 years yield an average of 1800-2450 g of resin per tree.

Genetic resources and breeding

The standard seed source areas for P. merkusii are Sumatra and Thailand. Seedlings raised from Sumatran seeds often miss the "grass stage" and are thus better suited for plantations. The sources of genetically superior P. merkusii seed in Sumatra should be protected. Natural stands of P. kesiya in the Philippines should be earmarked for seed collection and gene conservation. The natural areas of distribution of both species in Malesia are comparatively small, and for this reason, protection of natural stands should be guaranteed.

Seeds of P. caribaea are often imported from Fiji, Queensland (Australia) or Honduras (Central America), whereas seeds of P. oocarpa come from Belize (Central America).

International provenance trials of P. kesiya and P. merkusii have been established throughout South-East Asia and also in northern Australia; they are coordinated by the Commonwealth Forestry Institute of Oxford (UK).

In Thailand, trials of provenance hybrids of P. merkusii showed that hybrids of Thailand and Papua New Guinea provenances had better survival and length-growth than local provenances. P. merkusii seed orchards have been established in Indonesia.

Prospects

Pines are much planted trees because of their fast growth, ability to grow on comparatively poor soils and at high altitudes, and because of the detailed information available on their silviculture. The quality of the wood is, however, often very poor. The production of better quality wood from pine plantations should be a research priority.

Literature

Armitage, F.B. & Burley, J., 1980. Pinus kesiya. Tropical Forestry Papers No 9. Commonwealth Forestry Institute, Oxford. 199 pp.
Cooling, E.N.G., 1968. Pinus merkusii. Fast-growing timber trees of the lowland tropics No 4. Commonwealth Forestry Institute, Oxford. 169 pp.
de la Cruz, R.E., 1983. Technologies for the inoculation of mycorrhiza to pines in ASEAN. In: Te Aho, T. & Hosking, M.R. (Editors): Workshop on nursery and plantation practices in the ASEAN, Jakarta, Indonesia. New Zealand Forest Service, Wellington. pp. 94-111.
de Laubenfels, D.J., 1988. Coniferales. In: van Steenis, C.G.G.J. & de Wilde, W.J.J.O. (Editors): Flora Malesiana. Ser. 1, Vol. 10. Kluwer Academic Publishers, Dordrecht, Boston, London. pp. 447-452.
Farjon, A., 1984. Pines: drawings and descriptions of the genus Pinus. E.J. Brill, Leiden. 220 pp.
Greaves, A., 1982. Pinus oocarpa. Annotated bibliography No F22. Commonwealth Agricultural Bureaux, Slough. 70 pp.
Lamb, A.F.A., 1973. Pinus caribaea. Vol. 1. Fast growing timber trees of the lowland tropics No 6. Commonwealth Forestry Institute, Oxford. 254 pp.
Mirov. N.T., 1967. The genus Pinus. Ronald Press Company, New York. 602 pp.
Plumptre, R.A., 1984. Pinus caribaea. Vol. 2: Wood properties. Tropical Forestry Papers No 17. Commonwealth Forestry Institute, Oxford. 148 pp.
Wormald, T.J., 1975. Pinus patula. Tropical Forestry Papers No 7. Commonwealth Forestry Institute, Oxford. 172 pp.

Selection of species

Authors

Suhardi (general part),
M.S.M. Sosef (general part, selection of species),
P.B. Laming (properties),
J. Ilic (wood anatomy)