PROSEA, Introduction to Timbers

Introduction

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Definitions

This volume deals with timbers of South East Asia. The term "timber" is generally used for wood other than fuelwood, following primary conversion, in forms suitable for construction (especially for building houses, bridges and ships) and comparatively large in size. It is also used as a general term for forest crops and stands (hence the term "standing timber"). "Wood" is the hard, compact and fibrous substance between pith and bark of trunk and branches of a tree. Wood consists technically of the aggregated xylem elements intersected with the rays in many plants. In these definitions, the wood of a tree may be used as timber.

A "tree" is a perennial plant with a single woody self supporting stem or trunk which is usually unbranched for some distance above the ground and crowned with a head of branches and foliage. Foresters, when considering a tree mainly as a source of timber, often add to this definition a minimum height (4 m) and a minimum diameter of the trunk (7.5 cm) at breast height (1.5 m). Trees are very important elements of the landscape, not only by forming forests but because they are very common and predominant elements of the rural and semi urban landscape of most tropical countries.

A "forest" is defined as a large tract covered with trees, having a closed canopy and often with undergrowth. A natural forest is an extensive plant community of trees, shrubs and herbs in all stages of growth and decay having the quality of self perpetuation or of developing into an ecological climax.

Role of timber trees

Timber production and trade

Timber is very important in South East Asian countries in the present stage of their economic development. Malaysia and Indonesia are well in the lead of the exporting countries of tropical timber. In Malaysia the annual export value of tropical hardwood (logs, sawn timber and plywood) in the period 1985-1987 averaged almost US$ 2000 million, in Indonesia in the same period almost US$ 1750 million, which made timber the second most important export product after oil. From 1988-1992 the value of the exported timber was increased by levies; moreover, several tropical countries prohibited the export of non processed wood, to favour the domestic wood processing industry. This has made prices of exported timber increase considerably in recent years, and the export of sawn timber, veneer and plywood is currently an very important source of foreign exchange. For instance, from 1988 to 1989 the value of the export of plywood in Indonesia increased by 27%. In 1990 the 108 Indonesian plywood manufacturers exported plywood at an estimated value of US$ 3000 million. The total production of plywood in Indonesia is about 8 million m³/year. The annual export value of timber in the Philippines is much less, averaging about US$ 230 million in the period 1985-1987. The contribution of timber from Papua New Guinea on the world market has increased in recent years, but in Thailand, which was once an important exporter of timber, timber imports nowadays exceed timber exports (in 1991 Thailand imported tropical timber to a value of US$ 644 million, exporting timber to a value of only US$ 68 million). Singapore is an important intermediate port in timber trade; in the period 1985-1987 it marketed timber with a value of about US$ 370 million annually.

Export values of timber and wood products in South East Asia are listed in Table 1. The export of logs is very important in Sarawak and Papua New Guinea and the export of sawn timber in Indonesia, Sabah and Peninsular Malaysia. Plywood is the main export product from Indonesia and it has some importance in Peninsular Malaysia and the Philippines.

The demand for tropical timber continues to grow. The increase in the domestic timber requirements of the developing countries in South East Asia is estimated to be 6-10% a year. In 1989 the production of sawn timber in Indonesia was 10.2 million m3, whereas the export was only 2.7 million m³ (26%). On the other hand, in 1988 Sarawak exported more than 92% of the logs it produced, and Sabah more than 77%. The main importers of Malaysian and Indonesian timber are Japan (46%), other countries in East Asia (42%), the European Community (7%) and the United States (3%). In the period 1987 1990 Japan imported annually about 17 million m³ of timber (both processed and unprocessed) from South East Asia, which is about 20% of the total Japanese import. In the same period the European Community imported annually about 2.5 million m³ of timber from South East Asia.

Timber is usually graded into trade groups. The importance of timber trade groups varies with country, depending on the natural distribution areas of the timber species, since the most important groups are still harvested from natural forest. For Indonesia, the major timber trade groups (sawn timber) and their statistics for 1989 are listed in Table 2. Table 3 lists the most important groups and their statistics in 1992 for Peninsular Malaysia and Sabah. No statistics on trade groups for Sarawak are available, but the most important ones are meranti (Shorea spp.), keruing (Dipterocarpus spp.), kapur (Dryobalanops spp.) and ramin (Gonystylus spp.).

The major timber trade groups in Papua New Guinea are listed in Table 4. No export statistics are available.

The timber export in the Philippines is for the greater part confined to red lauan (Shorea negrosensis). The quantity of this timber (sawn) exported was about 750 000 m³ with a value of US$ 125 million in 1989, and 49 000 m³ with a value of US$ 10.5 million in 1990. Other important trade groups are white lauan (Shorea contorta) and apitong (Dipterocarpus), but their volumes and export value are much less (in 1989 about 45 000 m³ with a value of US$ 6 million for white lauan, and about 1600 m³ with a value of US$ 200 000 for apitong).

Teak (Tectona grandis) is by far the most important export timber of Thailand. The quantity exported in 1990 (processed) was 25 000 m³. Other export timbers, although of much less importance, are pra du (Pterocarpus macrocarpus) and para rubber (Hevea brasiliensis), which were exported (processed) in 1990 in amounts of about 8000 m³ and 320 m³, respectively.

Wood used for non timber purposes

Wood is also used for purposes other than timber, e.g. for pulp and paper and as firewood. The consumption of paper is burgeoning. The prognosis made by FAO in 1986 for 1990 was exceeded by 10%, resulting in a worldwide consumption of paper in 1990 of almost 250 million t. A further increase is expected in the coming years. This demand has resulted in plans for the establishment of new pulp mills and of plantations to supply them, mainly in Indonesia.

Many people depend on firewood as their chief source of fuel, and in parts of South East Asia the average user burns well over 1 t of firewood each year (National Academy of Sciences, 1980). With increasing human population and decreasing wooded areas, there is growing pressure on the forest for firewood (and timber for domestic use).

Excluded from this volume are plant species used primarily for paper making (to be dealt with in the Prosea Vol. 17: "Fibre plants"), and species whose primary use is firewood and allied applications (to be treated in Prosea Vol. 11: "Auxiliary plants in agriculture and forestry").

Grouping of timber trees

In 1989 a Prosea Timber Task Force was appointed to elucidate the large commodity group of timber trees and to propose how this group could best be treated in the Prosea Handbook. The Timber Task Force consisted of: I. Soerianegara (IPB, Indonesia), F.S.P. Ng and K.M. Kochummen (both FRIM, Malaysia); its advisers were R.J. Johns (Prosea Programme Leader Papua New Guinea) and S. Kadarsan (Prosea Programme Leader Indonesia); the coordinator was J.S. Siemonsma (Prosea Regional Coordinator South East Asia). In May 1990, this Task Force presented its report. A classification according to commercial importance was proposed: the major commercial timbers of South East Asia would be treated in Vol. 5(1), the minor commercial timbers in Vol. 5(2) and the lesser known timbers in Vol. 5(3). The choice of genera to be treated in each volume is rather subjective. What is now a lesser known timber may in the near future prove to be a major commercial timber. Conversely, commercially important timbers may rapidly lose their importance, for instance because of the depletion or conservation of stands. Nevertheless, this approach has important advantages over a complete alphabetical treatment: it enables important and well known timbers to be dealt with in greater detail than unimportant and lesser known ones, and omissions from the first two volumes have no serious consequences.

The timber trees in this volume are dealt with primarily by genus rather than by species. This is because trade groups of timber generally correspond more to genera than to species, and information on wood or timber is often not reducible to species. Furthermore, the genus approach reduces the large commodity group to manageable proportions.

After each genus treatment, selected species are described briefly. The selection of the species per genus is essentially based on their importance for the production of timber. However, it often proved difficult to determine the importance of a species on the basis of the availability of information on the use of the timber (e.g. for construction) or of the wood (e.g. for arts and crafts). In the absence of such information (the literature often only refers to genera or trade groups), those species known to reach a medium size (minimum height 20 m, minimum diameter of trunk 50 cm), and which are fairly common, at least locally, are included. Questionable choices are occasionally inevitable.

Botany

Taxonomy

Throughout Malaysia, Brunei and western Indonesia most lowland rain forests are dominated by a vast variety of tree species of the family Dipterocarpaceae. Dipterocarp genera and species represent a particularly valuable contribution to the world's timber resources and are the most important element in the productive forests of South East Asia. Dipterocarps are particularly important in the Philippines, where they provide 75% of the logs and 94% of the total volume. In Borneo, it is estimated that 67% of the total growing stock consists almost entirely of Shorea species, and in Peninsular Malaysia dipterocarps make up 50 60% of the total volume of the growing stock over 30 cm diameter and represent 75% of the commercial volume. In the semi evergreen forest in northern Thailand the dipterocarps make up 33% of the total growing stock (Dipterocarpus and Hopea), and the same predominance is found in Vietnam (Unesco, 1974). East of Borneo dipterocarps make up only a very small proportion of the big trees and there are few species.

Other important families for timber in South East Asia are Anacardiaceae, Apocynaceae, Bombacaceae, Burseraceae, Combretaceae, Ebenaceae, Euphorbiaceae, Fagaceae, Flacourtiaceae, Guttiferae, Lauraceae, Leguminosae, Magnoliaceae, Meliaceae, Moraceae, Myristicaceae, Myrtaceae, Rhizophoraceae, Rubiaceae, Sapindaceae, Sapotaceae, Sterculiaceae, Theaceae, Tiliaceae, Verbenaceae, and the Gymnosperm families Araucariaceae, Pinaceae and Podocarpaceae.

The tree species from large areas in South East Asia are not yet covered by modern floras. Flora Malesiana (van Steenis et al., 1950-), covering Brunei, Indonesia, Malaysia, Papua New Guinea, the Philippines and Singapore, is far from complete. The commercially important timber producing families which have been covered in Flora Malesiana include Anacardiaceae, Araucariaceae, Burseraceae, Combretaceae, Dipterocarpaceae, Fagaceae, Flacourtiaceae, Leguminosae (Mimosoideae), Magnoliaceae, Pinaceae, Podocarpaceae and Rhizophoraceae.

Indonesia has approximately 4000 tree species which are potentially useful for timber. Only about 400 species have current economic value, and about 260 species are classified as commercial timbers. A complete flora of Java is available (Backer & Bakhuizen van den Brink, 1963-1968), but other areas of Indonesia are covered incompletely or not at all. Over 3000 tree species occur in Peninsular Malaysia. The tree flora of Malaya (Whitmore & Ng, 1972-1989) covers all tree species of Peninsular Malaysia except dipterocarps which were covered earlier by Symington (1941). There are checklists and manuals for the trees of Sarawak, Sabah and Brunei (e.g. Smythies, 1965; Ashton, 1988). A flora of East Malaysia is in preparation.

Papua New Guinea, which together with Irian Jaya (Indonesia) and the Solomon Islands forms a biogeographical region occasionally known as Papuasia, has a mixture of floristic elements from Australasia and Malesia, to which Papua New Guinea belongs. Elements of Australasia are represented among the trees by genera such as Nothofagus, Casuarina and Proteaceae, elements of Malesia by the Fagaceae genera Castanopsis and Lithocarpus and the Dipterocarpaceae genera Anisoptera, Hopea and Vatica. Papuasia has well over 2000 species of trees, and some 120 genera are used in the trade for timber. Several endemic timber species of Papua New Guinea are suitable for use in reforestation or have potential for plantation establishment (e.g. Terminalia brassii). However, few tree species have been studied in detail, and even studies on the major commercial species are limited. Much research is still required, especially on the lesser known tree species (Johns, 1989). In Papua New Guinea only field keys and manuals are available for tree identification.

In the Philippines it is estimated that 3500 tree species have economic potential (Meniado et al., 1975). About 350 species are considered to have at least some economic importance. There has never been a good, comprehensive flora of the Philippines. The flora of the Philippines is probably the least known of any country in South East Asia. Most information is still based upon the work of E.D. Merrill (Merrill, 1923-1926). Recently, a flora of the Philippines project has been started.

About 540 useful tree species are recorded for Thailand, of which 59 are reported as useful timbers (Duriyaprapan et al., 1989). Teak (Tectona grandis) and Dipterocarpaceae supply most of the commercially important timber. Teak is important in the 5 provinces in the north west, covering an area of about 3 million hectares. Work on the flora of Thailand is currently in progress. The important timber producing families that have been dealt with so far include Ebenaceae, Leguminosae (partly), Magnoliaceae, Pinaceae, Podocarpaceae, Rhizophoraceae and Theaceae.

About 500 tree species are found in Vietnam. Most of the valuable timbers belong to the families Cupressaceae, Dipterocarpaceae, Leguminosae, Meliaceae, Podocarpaceae and Sapotaceae. Among the families published in the current Flora of Cambodia, Laos and Vietnam (Flore du Cambodge, du Laos et du Viêtnam, 1960-) are Anacardiaceae, Combretaceae, Dipterocarpaceae, Flacourtiaceae, Leguminosae (partly), Rhizophoraceae and Sapotaceae.

Approximately 2300 tree species are found in Burma (Myanmar). Only a few of these are extensively used for timber, and the knowledge of tree species is very limited. Teak is the main species producing timber, sometimes occupying over 10% of the area of the economically important deciduous forest. It is even estimated that teak accounts for 10-15% of the total volume of growing stock of the mixed deciduous forests in Burma (Unesco, 1974). Burma has always produced the largest quantity and the best quality teak. Teak and "padouk" (Pterocarpus macrocarpus) are often planted for timber production (San Maung, 1989). The only existing flora of Burma dates from the 19th Century (Kurz, 1877).

It is clear that up to date taxonomic information on tree species is limited in many parts of South East Asia. Taxonomic information is fundamental for an understanding of the threatened tropical rain forest, but even at the most elementary levels of organisms of the forest (i.e. the trees) this kind of information is often lacking or very incomplete. Forestry research should be accompanied by taxonomic research, but this combination is seldom practised.

Morphology

Tree architecture

Hallé, Oldeman & Tomlinson (1978) distinguish 23 architectural models of trees. The models are monoaxial (with a single apical meristem and consequently a single axis), or polyaxial (with several morphologically distinct axes, derived from more than one meristem). The first group (2 models) is represented by palms and comparatively small dicotyledons. In the polyaxial trees the following types are distinguished:

1. Vegetative axes all equivalent and orthotropic; 4 models are distinguished. Multiple stemmed palms are particularly important in this group.

2. Vegetative axes differentiated into trunk and branch; 14 models are distinguished. The most important models for timber trees of South East Asia are briefly described below, and illustrated semi diagrammatically in Fig. 1.

• Aubréville's model. Monopodial trunk with rhythmic growth and spiral or decussate phyllotaxis, bearing whorled branch tiers with similar phyllotaxis; branches growing rhythmically but modular, each branch plagiotropic by apposition; inflorescences lateral and modules consequently growing indefinitely. Examples: Campnosperma brevipetiolatum, Endospermum diadenum, Fagraea fragrans, Palaquium gutta and Terminalia catappa.
• Massart's model. Orthotropic monopodial trunk with rhythmic growth and consequently producing regular tiers of branches at levels established by the growth of the trunk meristem; branches plagiotropic either by leaf arrangement or symmetry, but never by apposition; position of flowers not significant in the definition of the model. Examples: Ceiba pentandra, Dipterocarpus costulatus and Shorea ovalis.
• Roux's model. Orthotropic monopodial trunk meristem showing continuous growth; branches plagiotropic and usually inserted continuously; leaf arrangement spiral on the trunk but usually distichous on the branches; position of the flowers not significant in the definition of the model, but mainly lateral on the branches. Examples: Dryobalanops sumatrensis, Durio zibethinus and Hopea odorata.
• Rauh's model. Monopodial trunk growing rhythmically and so developing tiers of branches which are morphogenetically identical to the trunk; flowers always lateral and having no effect on the growth of the shoot system. One of the most common models. Examples: Araucaria cunninghamii, Artocarpus heterophyllus, Pinus merkusii and Swietenia macrophylla.
• Attim's model. Axes with continuous growth, differentiated into a monopodial trunk and equivalent branches; branching either continuously or diffusely; flowers lateral and not affecting shoot construction. Examples: Casuarina equisetifolia, Lumnitzera racemosa, Calophyllum spp., Ceriops tagal and Rhizophora mucronata.

3. Mixed axes; meristems determining both trunk and branch axis; 3 models are distinguished. The most important model for South East Asian timber trees is:

• Troll's model. Axes all plagiotropic with continual superposition, mainline axes contributing part trunk, part branch, the proximal part becoming erect; distal part of each axis being a branch with or without determinate growth, bearing lateral axes which often do not form a basal erect portion. The most common model, particularly in Leguminosae. Examples: Albizia lebbeck and Pterocarpus indicus.

Trunk, root system and bark

The trunk is the main stem of a tree. The lower merchantable portion of the trunk is often called "bole", and the length of the clear bole, up to the first limbs, is of interest for timber production. The bole may be columnar or tapered, straight or crooked. For most timber purposes straight and columnar boles are preferred. Sometimes the bole is fluted. The trunk often has buttresses: large flanges protruding from the lower part of the trunk. They may give support to the trunk in trees with superficial rooting. Buttresses are a valuable guide to the identification of trees in the forest. Plank roots (horizontal roots extending vertically resulting in wavy, plank like structures growing away from the base of the trunk, e.g. Heritiera littoralis, can be considered as a form of buttress.

Aerial roots are particularly common in species growing in swamps. There are several types of aerial roots including stilt roots (branched, looping aerial roots that arise from the trunk and lower branches, e.g. Rhizophora spp.), pneumatophores (erect lateral branches of buried horizontal roots which arise above the level of the substrate, e.g. Avicennia spp.), and root knees (horizontal roots forming a pronounced loop above the level of the substrate, e.g. Bruguiera gymnorhiza.

The bark surface often provides important characters for identification. The bark of some species nearly always has a distinctive colour, e.g. tualang (Koompassia excelsa) tinged a delicate fluorescent green. The bark surface may be smooth, dimpled (e.g. kasai (Pometia pinnata) has a surface mottled in colour with small round scales), scaly, fissured (e.g. bintangor (Calophyllum spp.)) or scrolled (e.g. Tristaniopsis spp.). Sometimes the outer bark can be removed to show a prominently coloured "middle bark" which is the innermost cork layer (e.g. Lophopetalum spp. have an ochre or orange middle bark). The inner bark (bast) is of less value for identification, but colour, texture, exudates and smell do provide diagnostic characters.

Wood

In a cross section of the trunk the wood portion often has a distinctive outer and inner layer (see Fig. 2). The outer layer consists of wood that is young and living or physiologically active. It is usually paler than the inner wood, permeable and not durable. This "sapwood" is separated from the bark by a formative layer of cells called "cambium". The central portion of the wood is called "heartwood"; it is usually darker and less permeable than the surrounding sapwood but sometimes difficult to distinguish. Often resins, gums, tannins or other coloured organic substances are present in the heartwood, which may function as deterrents to fungi and insects. The heartwood is more durable than the sapwood, and because of the presence of extractives, is also heavier after drying. The pith is situated in the very centre of the heartwood and consists of a usually sclerified longitudinal strand of parenchyma tissue. Throughout, the wood is traversed by wood rays running radially from the pith or a more peripheral part of the wood to the cambium and continuing in the bark as phloem rays.

Three major planes are distinguished for sawing or for describing macroscopic or microscopic features (Fig. 3):

• Transverse, end grain, or cross section: the plane perpendicular to the log.
• Radial or quarter sawn: vertical plane through the central axis of the log (parallel to the rays).
• Tangential, flat sawn or back sawn: vertical plane parallel to but not intersecting the longitudinal axis.

The growth of the wood is sometimes discontinuous as a result of less favourable growing conditions. This may result in growth rings in the wood. In the tropics growth rings are often present in trees growing in areas with a pronounced dry season, e.g. teak (Tectona grandis). Evergreen trees of the rain forest often lack distinct growth rings, but growth rings are more common in tropical trees than is suggested in the general literature, although they may not be annual (Baas & Vetter, 1989).

Wood anatomy

Detailed standardized accounts of the wood anatomy have been included in all generic treatments because microscopic wood structure is basic to an understanding of wood properties and crucial for timber identification. In a broader context, microscopic wood structure is also crucial for the understanding of processes within the living tree because it fulfils a combination of four vital functions: mechanical support, long distance transport of water and minerals from the roots to the transpiring leaves and flowers, storage and mobilization of reserve carbohydrates, lipophilic compounds and proteins, and the ability to resist pathogens after wounding or to compartmentalize decay by the formation of various types of barrier zones to micro organisms.

On a global scale, there are strong correlations between the wood structure and macro ecology of tree species. Hardwoods of the tropical lowland forests typically have a hydraulically efficient system of wide and simply perforated vessels. Axial parenchyma is often abundant, or its function in storage and defence is taken over by living libriform fibres. Fibres range from thin to thick walled, in close correlation with the density and hardness of the timber, and reputedly also in close correlation with the successional status of the species. However, the observation that some fast growing pioneer species (e.g. Macaranga) produce much lighter woods with thin walled fibres than slow growing climax species cannot be generalized and has many exceptions.

The descriptive format in this volume follows generally accepted standards. For hardwoods, details are given on growth rings; vessel distribution, frequency, diameter, element length, type of vessel perforation, and lateral wall pitting; fibre length, fibre wall thickness and pitting; axial parenchyma distribution and strand length; ray frequency, size, and composition; mineral inclusions (crystals and/or silica bodies) and their distribution; secretory elements such as resin or gum ducts, laticifers, etc. The terms and definitions adopted are those of the IAWA (International Association of Wood Anatomists) List of Features for Hardwood Identification (IAWA Committee, 1989. IAWA Bulletin n.s. 10: 219-332). For the limited number of South East Asian softwoods (which, like all conifers, lack vessels), another descriptive format, with emphasis on crossfield pitting and ray parenchyma and ray tracheid cell wall features, has been adopted.

Growth and development

Trunk and branch formation and growth rhythm

The trunk of a tree results from the dominance of one main axis (i.e. one meristem) over all others (Champagnat, 1978). This axis is usually the epicotyledonary axis of the seedling. If the epicotyledonary axis is destroyed, it can be replaced by a shoot from a distal position from the remaining part. There is no branching of the young trunk. In somewhat older individuals, dominance is diminished and several terminal shoots may arise. However, one of these becomes dominant, and the others die. Later, the first persistent branch appears, the first element of the crown. The height of the crown depends not only on the species but also on environment, planting distance, etc.

Saplings of many tropical trees have been reported to remain evergreen and show continuous, monopodial growth for 2 3 years or until they reach a height of several metres (Borchert, 1978). With increasing size, growth is often discontinuous or regularly rhythmic (flushes). Discontinuity of development is the rule in a temperate climate with winter dormancy and in a tropical climate with a pronounced dry season, but it is also common in a more or less uniform tropical climate such as that prevailing in Singapore. Tree species which exhibit continuous growth do exist, but they do not appear to reach exceptional dimensions and are not very common in the tropics. The intervals between growth flushes vary among species, climatic regimes, individual trees within species, and even branches of a given tree (Kramer & Kozlowski, 1979). Little is known about climate dependent growth or about slow and progressive endogenous changes that are independent of the environment. Much experimental work is needed in order to define the regulatory mechanism of growth rhythms in the tropics.

Tropical trees exhibiting rhythmic growth are usually asynchronous in regard to growth flushes when they are young, but invariably show close synchronism in growth behaviour when mature. This seems to indicate the presence of an external triggering stimulus (Alvim & Alvim, 1978) which may be photoperiodic, thermoperiodic or hydroperiodic.

In young trees the amount of annual shoot growth increases for a number of years but attains a maximum rate relatively early in the life of a tree, and gradually declines thereafter. Height growth of tropical trees may not exceed that of temperate trees, or exceed 2 m a year, particularly in saplings and coppice shoots. Rapid rates of growth are often found in trees growing in the open or at the forest edge. The rate tends to be much slower inside the forest.

The growth of all or most tree species is supported by the existence of mycorrhizae, a symbiotic relationship between the roots and fungi whereby nutrient uptake of the tree roots is facilitated. Most legumes have bacterial nodules which are capable of fixing atmospheric nitrogen to improve soil fertility.

Crown formation

The shapes of tree crowns differ greatly among species occupying different height levels of the tropical forest, the tallest trees having the widest and flattest crowns. In the second layer tree crowns are about as wide as they are high, while in the lower or third layer they are often tapering or conical. The angles of branching tend to be upwardly oriented in upper strata and more horizontally oriented in the third layer. In many species the crown form changes progressively during development when passing through the different forest strata. Crown forms are also greatly modified by site. Aspects of tree form such as branch angle, amount of branching, amount and duration of shoot growth, and degree of apical dominance are genetically controlled, but they can also be modified by the environment (Kramer & Kozlowski, 1979).

Solitary trees tend to have larger crowns than those growing in plantations. In a young, even aged stand all trees may have more or less similar crown shapes, but with increasing age, competition intensifies as the crowns begin to close the canopy. Trees of some species come to occupy low positions in the canopy whereas these of others become dominant because they are the largest and most vigorous.

Leaf shedding

Leaf shedding of individual trees usually does not occur continuously in evergreen, tropical forests, but there are peaks of leaf abscission. Trees may be bare for a period and flower on the bare crown (deciduous trees), or leaf fall may occur at about the same time as bud break (leaf exchange); finally, leaf fall may occur well after bud break and leaves of several flushes sometimes occur together on one tree (evergreen trees). Leaf shedding of many rain forest species is easily induced, even by mild water stress (Kramer & Kozlowski, 1979). Leaf fall is closely related to the local dry season. However, when the rainy season is accompanied by waterlogging of the soil, leaves may drop because of insufficient aeration of the roots. Some species grow or can be grown both in permanently moist and seasonally dry regions (e.g. teak) and their habit may vary from evergreen to deciduous and they may display significant differences in shoot growth patterns. However, a genetically determined lifespan of leaves has also been suggested (Whitmore, 1990).

Wood formation

The wood producing capacity of a tree depends on the interaction of 3 major components (Kramer & Kozlowski, 1979):

• The rate of photosynthesis per unit of leaf area or of mass or per unit of chlorophyll.
• Structure, duration, exposure and area of canopy.
• Differences in distribution and partitioning of photosynthates among the various organs of the tree, resulting in different ratios of dry matter in the crown, bole and roots.

Of course, the increment in diameter may also be influenced by environmental conditions. Tree species compete with each other in a forest stand for space, light, nutrients and water. Hence, root competition should be considered when establishing plantations. Some tree species produce toxic substances which may assist in avoidance of competition with other species; such substances consist of phenolic acids, quinones, etc. However, such allelopathy has seldom been demonstrated (e.g. in Ailanthus).

Flowering and seeding

Although some tropical trees flower continuously throughout the year (particularly pioneer species), most of them have a distinct flowering season although individuals may flower irregularly. Some species show mass flowering at indefinite intervals, with practically every individual of that species in flower at the same time over a wide area (often when rain and associated cooling follows a period of drought). An example is Pterocarpus indicus. Nearly all species and individuals of dipterocarps in a certain area may flower simultaneously at more or less irregular intervals of 2-10 years. The area may be as small as a river valley or as big as north eastern Borneo. Other trees (e.g. trees of the families Burseraceae and Sapotaceae) also flower heavily in a good dipterocarp year, and it is possible that a climatic factor is involved. Mass flowerings coincide with exceptionally dry weather, but the exact nature of the trigger has not yet been established (Whitmore, 1990). Some dipterocarps, however, flower and fruit every year, e.g. Anisoptera thurifera in New Guinea.

Vigorous, dominant trees produce more seed than intermediate or suppressed trees; trees of the latter category often fail to produce any seed. The seeds of most trees in forests of South East Asia germinate within a few days of shedding; those that do not germinate within a few weeks usually die. This means that the forest soil does not hold a reservoir of seeds and therefore these trees are vulnerable to extinction by logging if not many seedlings are already established and survive the logging operations. This also means that seeds can only be stored for a short period. Many species of tropical trees have comparatively large seeds, which enables their seedlings to establish under dense shade (because of the large amount of food reserves), waiting for a gap to appear in the canopy before growing upwards. On the other hand, large seeds have a limited dispersal ability, except when they are dispersed by animals such as birds and bats. Consequently, large quantities of seedlings are found close to the mother trees. Predation of seedlings, e.g. by ants, can be considerable. It is possible that predators are attracted to concentrated stands of seedlings, giving the few furthest dispersed seeds a better chance of survival (Ng, 1978). Mass fruiting of dipterocarps may be advantageous for seed survival.

Those commercially important timber trees which are pioneers have small seeds. Examples are Alstonia angustiloba and Anthocephalus chinensis.

Longevity

The longevity of trees varies greatly. Trees can become very old, particularly some species from temperate regions, where ages of well over 5000 years have been reported. Tropical trees usually die earlier, but several species can reach a considerable age. Trees show several common symptoms of ageing: decrease of metabolism, decrease in the proportion of photosynthetic to non photosynthetic tissue, gradual reduction of growth of vegetative and reproductive tissues, increase in dead branches, slow wound healing, increased susceptibility to injury from certain insects and diseases and from unfavourable environmental conditions, and loss of geotropic responses.

Silvicultural treatments

Most silvicultural treatments practised in plantations are successful only insofar as they improve the physiological functioning of trees. In forestry the primary crop is the stem of the tree, and hence the factors which determine the growth rate and form of the stem are of major concern. Much interest has been shown in crown sizes because of their influence on wood production. After the crowns close, the lower branches die and the live crown ratio (percentage of total tree height occupied by functional branches) decreases. When the live crown ratio decreases below a critical value (often about 40%), the rate of wood production diminishes greatly. Thinning at this stage may result in increased wood production of single trees because it results in a larger leaf area which is accompanied by more photosynthesis and general physiological activity of the crown. However, thinning may produce a more tapered trunk because the increase of cambial activity and radial growth towards the base of the tree is greater than in the crown. This may be misleading when using the increase of diameter growth at breast height as an indication of the actual increase of total volume of wood. In natural forest, the live crown ratio is approximately 30% and trees grow comparatively slowly.

Ecology

Climate

In the tropics, climatic differences are primarily determined by the amount and distribution of rainfall (the absence or presence - and duration - of a dry season), and secondarily by differences in elevation. The climatic types of tropical South East Asia fall into zones V1 (tropical rainy climate, 9.5-12 humid months per year) and V2 (tropical humid summer climate, 7-9.5 humid months per year) as defined by Troll (1966); zone V3 (wet and dry tropical climate, 4.5-7 humid months per year) occurs only in central Thailand. Schmidt & Ferguson (1951) used the following equation to distinguish rainfall types in Indonesia:

     average number of dry months

Q == × 100

     average number of wet months

Whitmore (1984) produced a climatic map of South East Asia based on the rainfall types of Schmidt & Ferguson, but simplified it by uniting types C and D, and also E and F (types G and H occur only very locally in Sulawesi). Table 5 compares the climatic types. It should be noted that a sound comparison of the classifications of Schmidt & Ferguson and Troll is not possible, although both classifications are based on the number of humid months per year. This is because Troll defines his climatic types on a global scale and his classification is much less detailed for South East Asia, or because his definition of a humid month is different from what Schmidt & Ferguson call a wet month. The climatic zones of Troll in Table 5 have been derived by comparing his (global) climatic map with the climatic maps of Indonesia and South East Asia produced by Schmidt & Ferguson and Whitmore, respectively.

Peninsular Malaysia, most of Sumatra and Borneo, the eastern parts of the Philippines, central Sulawesi and most of New Guinea have rainfall type A (perhumid). Rainfall type B (slightly seasonal) is found in southern peninsular Thailand, some areas in northern, western and southern Sumatra, south western Java, southern and eastern Borneo (and northern Sabah), the central part of the Philippines, parts of southern, northern and eastern Sulawesi, most of the Moluccas, and parts of New Guinea (particularly in the south). Rainfall type C+D (seasonal) occurs in most of Thailand, Indo China, a small area of northern Sumatra, northern, central and eastern Java, the western parts of the northern and southern Philippines, parts of Sulawesi and the Moluccas, and parts of Papua New Guinea (but not in the centre and west). Rainfall type E+F (strongly seasonal) is confined to the extreme north of Sumatra, parts of East Java, most of the Lesser Sunda Islands and Timor, two small areas in western Sulawesi, Waigeo Island (Irian Jaya), and a small area around Port Moresby (Papua New Guinea). In seasonal climates, water stress during the dry season may cause tree growth to stop.

The mean temperature usually falls by approximately 0.6°C for every 100 m increase in altitude. Rainfall tends to increase with elevation up to a certain altitude, but then it decreases. At higher altitudes solar radiation is more intense than in lowlands, but the average annual duration of sunshine in the cloud zone is less, thereby making the total solar radiation less than in the lowlands. These factors have a profound influence on the composition, structure and productivity of forest vegetation, and give rise to altitudinal zonation, although scientists disagree about the details of how forests are influenced by this change in climate.

The existence and extent of forest in a certain area influences the climate, primarily because of the evapotranspiration. This is a complicated subject on which knowledge is improving, but is still very incomplete. See Bruijnzeel (1990) for more detailed information.

Soils

Edaphic conditions can also give rise to distinct forest formations. The major soil groups are (Dudal, Moorman & Riquier, 1974):

• Entisols (alluvial soils and regosols). Young sediments without prominent horizons; occurring in floodplains, valley bottoms, coastal zones, footslopes and volcanic areas throughout South East Asia.
• Vertisols (grumusols). Dark, heavy clay soils with well developed horizons; found in Indo China, central Thailand, eastern Java, the Lesser Sunda Islands and Luzon.
• Inceptisols (andosols and acid brown forest soils). Young, shallow soils, weathered from volcanic ash under humid conditions and found in areas subject to continual erosion; occurring in volcanic areas and on mountains and steep hills throughout South East Asia.
• Spodosols (podzols). Very acid, bleached, light textured (sandy) soils with horizons rich in organic matter and iron oxides; occurring in lowlands, particularly in southern Thailand, eastern Peninsular Malaysia and Borneo.
• Alfisols (especially red yellow podzolic soils and red brown earths). Neutral to acid soils, especially kaolinitic clays. These are the dominant soils in South East Asia, occurring all over the region but particularly in the western part.
• Oxisols (dark red, reddish brown, red and yellow latosols). Acid, clayey or more sandy soils; occurring in western Thailand, Sumatra, Java, Bali, Borneo, the Philippines and the Moluccas.
• Histosols (organic soils). Acid soils with over 30% organic matter, peaty soils in poorly drained situations; occurring commonly in Peninsular Malaysia, eastern Sumatra and Borneo.

Soil erodibility is a very important soil characteristic and should be considered in relation to forestry activities. Oxisols are much less erodible than entisols, inceptisols and alfisols. Mountains and hills must have sufficient forest protection in order to prevent erosion.

Soil fertility should be maintained in forest plantations. Short rotation periods may rapidly impoverish the soil, making fertilization necessary.

Forest classification

Whitmore (1984) distinguished major forest formations on the basis of climatic and edaphic conditions. The forest formations are briefly described below, and some characteristic trees are mentioned. For convenience, some of Whitmores formations have been combined.

• Tropical lowland evergreen rain forest. This is the predominant forest formation in South East Asia; it occurs in places where water stress is absent or only brief and intermittent, from sea level up to 1200 m altitude. It has the largest number of species. In western Malesia dipterocarps are dominant (especially species of the genera Shorea, Dipterocarpus, Dryobalanops, Parashorea and Anisoptera). The forest trees are very tall.

• Tropical semi evergreen rain forest. This type of forest formation is predominant in the seasonal regions of South East Asia; it occurs in places with regular annual water stress due to rainfall regime or soil conditions (e.g. marginally to evergreen rain forest in Indo China and Thailand, in the Lesser Sunda Islands and in rain shadow areas in New Guinea). It includes both evergreen and deciduous trees. The number of species is high but less than in the evergreen rain forest, and it contains fewer dipterocarps.

• Heath forest (also called "kerangas"). Heath forest develops over coarse siliceous deposits giving rise to podzols. It occurs particularly in Borneo. The storey formed by large saplings and small poles predominates and the canopy is low and uniform. Dipterocarps, mainly heavy wooded species, are often dominant among the larger trees (e.g. Cotylelobium, Hopea (giam) and Shorea (balau) species); other common trees include Cratoxylum, Eugenia and Agathis species. Heath forest should not be exploited because of its fragility. Natural regeneration is often very slow because of the extreme poverty of the soil.

• Forest on limestone and ultrabasic rocks. Limestone hills provide a diversity of habitats and soils but the forest has no commercial value. Forest on ultrabasic rock is often derived from the surrounding forest and sometimes not clearly demarcated from it, but may in other places have a distinct species composition.

• Beach vegetation. On the beach ridge (the low ridge at the inland margin of a sandy beach) a vegetation type is found that is called the Barringtonia association. It forms a forest fringe that is seldom more than 50 m wide. Typical tree species include Barringtonia asiatica, Calophyllum inophyllum, Casuarina equisetifolia, Cocos nucifera, Terminalia catappa and Hibiscus tiliaceus.

• Mangrove and brackish water forest. These forest formations occur in estuaries, deltas and mud flats subjected to regular tides. Brackish water forest forms the inland edge of mangrove forest. Typical species are Avicennia, Bruguiera, Rhizophora and Sonneratia species, and also Excoecaria agallocha and the palm Nypa fruticans. Mangroves are (or were) valuable sources of firewood, charcoal, tannin and poles for piling and scaffolding; Rhizophora species produce chipwood. See Tomlinson (1986) for more detailed information.

• Peat swamp forest. A very special type of forest is found on peat soils, which are acid and fed only by rain water. It is particularly widespread in eastern Sumatra, near the coasts of Peninsular Malaysia, Borneo and Irian Jaya. The forest often has distinct zones from the outer part of the peat swamp to the inner part. Characteristic species are: Copaifera palustris, Cratoxylum arborescens, Dactylocladus stenostachys, Dryobalanops rappa, Gonystylus bancanus, Shorea albida (northern Borneo) and Tetramerista glabra. Several of these species are very interesting from a commercial point of view (for timber).

• Freshwater swamp forest. This type of forest occurs where the soil is regularly inundated with mineral rich fresh water. The pH of the soil is higher than in peat swamp. The swamp may be permanent, or the soil surface may dry out periodically. Freshwater swamp forest occurs over large areas near big rivers, for instance in New Guinea. Some typical trees are Alstonia, Campnosperma, Dyera, Melaleuca and Palaquium species. Freshwater swamp forests are generally of low commercial value except for some areas with almost pure stands (e.g. Campnosperma stands in Malaysia and Papua New Guinea).

• Monsoon forest and tropical moist deciduous forest. These forest formations occur in a seasonal climate where water is periodically limiting to plant growth. They occur over large areas in Burma and Thailand, and only locally in Malesia (in rain shadow areas). The trees are usually deciduous, and the undergrowth is regularly burned. The most important commercial timber species is teak (Tectona grandis); other characteristic species are Dalbergia latifolia (Thailand, Java) and Eucalyptus species (Papua New Guinea).

• Montane forest formations. By comparison with lowland rain forest, the montane rain forest has a lower canopy, with fewer, smaller emergent trees. Upper montane rain forest has a low, flattish canopy, with slender trees often with gnarled limbs and dense subcrowns, and has a sharp lower boundary. Lower montane rain forest merges into lowland rain forest; the lower boundary of montane forests depends on the region. Trees occurring in seasonally dry sites in the lower montane zone are Pinus and Araucaria species. Shorea platyclados is by far the most common lower montane dipterocarp in Peninsular Malaysia, and in New Guinea lower montane forest is often dominated by Castanopsis and Nothofagus species.

Properties

The wood properties of the timber trade groups are treated under the heading "Properties" of each entry. The Table on wood properties of selected species (see pages 475 499) gives the physical and mechanical properties of species for which information is available. The different wood characteristics (in the order in which they are dealt with in the entries) are discussed briefly below.

• Colour. The colour is important for application of the wood as well as for identification. For this reason, it is described both in the Section "Properties" and in the Section "Wood anatomy".
• Density and moisture content.

weight (kg) Density = at a certain moisture content. volume (m³)

Often the density is given at a moisture content of 15%, but sometimes at other moisture contents (when no information is available at 15%). The moisture content greatly influences the density.

The moisture content is determined by measuring the weight of the water in the wood, expressed as a percentage of the dry weight of the wood (approaching 0% moisture content). The moisture content before drying is

weight before drying dry weight <x> 100% dry weight

The moisture content of green (fresh) wood can be much more than 100%, especially in lightweight timbers having comparatively little wood substance and large cell cavities. It can also be measured by using an electric moisture meter.

• Grain and texture. The grain defines the arrangement or alignment of wood tissue. The texture is largely determined by the size and arrangement of the vessels, differing from very fine to coarse. Grain and texture influence the uses of wood (e.g. for veneer) and also contribute to its identification.
• Mechanical properties. Mechanical properties (strength properties) are important to determine the structural use of wood. They represent the resistance of the wood to certain external forces which cause tension and deformation. Strength properties of wood largely depend on the density and moisture content, which is why these are cited (where known) for species in the section "Selection of species".

The mechanical property data have been obtained using either the American ASTM (American Society for Testing Materials) method D143-52 or the British Standard No 373. These testing systems are roughly identical. However, sometimes the test samples used differ in size and shape (e.g. for determination of the shearing strength); then the figures are not completely comparable between the systems. For most tests, wood specimens (without defects) of 50 mm × 50 mm and of various length are used. Strength values of wood in general use are also influenced by defects, duration of loading, moisture content and dimensions.

The modulus of rupture is a measure of the load carrying capacity in bending until breaking occurs. The modulus of elasticity measures the stiffness of beams or long columns. Compression tests on comparatively small wood specimens parallel (maximum crushing strength) and perpendicular (stress at limit proportionality) to grain give the figures for compression strengths. The shear strength measures the resistance of wood when the forces acting on it tend to make one part slide over another in the direction parallel to the grain. Cleavage (resistance to splitting) is of importance when wood is to be nailed or bolted; it may differ considerably with the plane of cleavage, with radial splitting occurring more readily than tangential. The Janka hardness is the load required to embed a steel ball to half of its diameter, causing a depression of 100 mm2; Janka end hardness is determined on transverse sections, Janka side hardness is the average of tests on radial and tangential surfaces. Janka hardness is a measure of the resistance of the wood to indentation, and also indicates the ability to withstand abrasion.

• Shrinkage and drying. Shrinkage figures are given from green condition to 15% and/or 12% moisture content and/or oven dry. Shrinkage causes deformation of wood during drying when it is high and when it differs considerably in radial and tangential direction. Information is given on the response of the wood to air drying (seasoning) and kiln drying. For kiln drying, schedules used in Indonesia (recommended temperatures and corresponding relative humidity) or Malaysia (kiln drying schedules, see Table 6) are given in the entries. The Malaysian kiln drying schedules are designed for use with timbers up to about 40 mm thick, dried in a forced draught kiln. Thicker dimensions require somewhat higher humidities to prevent severe moisture gradients from developing. When drying timber 40 75 mm thick, the relative humidity should be 5% higher at each stage of the appropriate schedule, and 10% higher with wood 75 mm or more thick.

Kiln schedule A is suitable for timber which must not darken in drying and for timber which has a pronounced tendency to warp but is not particularly liable to check. Schedule B is suitable for timber that is very prone to check, and schedule G for very slow drying timber that is not particularly prone to warp (Pratt, 1986).

• Working properties. Much of the information given on working properties is highly subjective as they can only be described and are not quantifiable.
• Veneer and plywood. Veneers are thin wood sheets made by peeling (most common), slicing or sawing. Some timbers can be peeled without pretreatment, but sometimes heating by steaming or boiling is needed. The quality of the veneer is also influenced by the quality of the logs, thickness of the veneer and peeling angle. The bonding strength of plywood made of veneers is often evaluated by the Japanese JAS type II standard, the German DIN 68075-IW 67 standard or the British standard.
• Durability and treatability. Durability is usually classified in 4 (tropics) or 5 (temperate regions) groups (see Table 7). The usual way to test durability is to bury test sticks of 50 mm × 50 mm in cross section of the heartwood in the ground. The actual service life of timber in common usage is often considerably longer. Sapwood is much less durable than heartwood, usually perishable. The durability classification in Indonesia differs slightly (see Martawijaya et al., 1986). In addition, durability classifications in Indonesia exist which are based on the resistance to wood destroying fungi (in laboratory tests) and the resistance to dry wood termites (Cryptotermes cynocephalus).

The treatability of wood depends on the permeability for preservatives. Classifications are for heartwood only (sapwood is usually more permeable) and should be used with caution because evaluations are non standard. Some classifications are based on pressure treating systems, others on non pressure systems, and a wide range of specimen sizes, with or without end coatings, is used.

• Chemical properties. The chemical composition of wood is important for the yield and quality of pulp. Cellulose is the basic material for pulp which is used for the manufacture of paper. For good paper, a low percentage of lignin is required. Pentosan functions as inter fibre bond in paper manufacture. The solubility in solvents such as alcohol benzene, cold and hot water and NaOH solution is related to pulp production, especially to the quantity of chemicals required to process the pulp.

A high percentage of silica easily blunts sawteeth, but can make wood resistant to marine borers, together with suitable organic substances.

• Energy value. The energy values as given in the entries are for oven dry wood. They vary within a small range, roughly between 17 000 21 000 kJ/kg. A high energy value indicates suitability as fuel.

Wood processing

The global timber trade started with the export of logs from the resource rich countries in the tropics to industrialized western countries where almost all the wood processing industries were located. With gradual industrialization, the developing countries began to establish the relatively less capital intensive and simple saw milling industries to convert the logs into sawn timber of different dimensions. To fetch higher prices, a system of grading was introduced. The Malaysian Grading Rules for Sawn Hardwood Timber are still widely used in the timber trade. For higher added value, an increasing quantity of sawn timber is kiln dried before shipping.

The veneer, plywood and blockboard industries were the next major primary processing industries to expand in the resource rich countries. The manufacture of veneer and plywood requires the input of large and round logs, whereas the core of blockboard is usually made from the peeler cores. Malaysia has a well developed and export oriented plywood industry which produced 1.5 million m3 of plywood and 0.7 million m3 of veneer in 1991 in its 99 factories. The growth of the Indonesian plywood industry is impressive: the plywood/veneer production capacity increased from 4.6 million m³ to 8.2 million m³ from 1985-1988, and the export of plywood (produced in 108 factories) reached 8.5 million m3 valued at over US$ 3000 million in 1990. The large outputs of processed wood from Malaysia and Indonesia have led to the decline or demise of similar industries in Korea, Singapore, Taiwan and Japan, which were traditionally dependent on log supply from Malaysia and Indonesia.

The growth of primary processing industries invariably generates a substantial amount of wood residues providing the impetus for the development of other wood based industries which can utilize small logs and wood chips. There is a considerable increase in particle board production in the countries of South East Asia. Research has further indicated the suitability of rubberwood for the production of medium density fibreboard (MDF) which is in high demand for furniture manufacture. Several MDF plants have been established in Malaysia during the last 3 years and a similar development trend has been observed in Thailand and Indonesia.

With the increase in literacy, the demand for pulp and paper is growing rapidly. Thailand, Indonesia and Malaysia have increased their pulp and paper production in the last few years, based either on pulp from indigenous tree species, plantation wood and bamboo, or recycled fibre.

The current emphasis in most resource rich countries is to further promote downstream value added processing industries within the countries and to control, limit and even ban the export of logs and rough sawn timber. Semi finished products in the form of mouldings, laminated timbers and furniture components have become important export items. Several countries have even ventured into the production of finished products such as furniture, doors and utensils for export.

It is expected that in the near future very few countries will remain in the business of exporting logs, rough sawn timber or general utility plywood. The global timber market will be offered a wide range of further processed products from the resource rich countries. The sawn timber exported will be mostly in kiln dry condition and the plywood will be available with various types of overlays ready for specific uses, including the phenolic film faced concrete shuttering board and container flooring. Most countries in the tropics are now concentrating on securing a share of the lucrative wooden furniture market through increased production of high quality and well designed furniture.

Forest management

Forested lands are managed for a multiplicity of purposes, usually with one dominant use, most often timber production. The basic aim of forest management is to keep forest lands productive. "Sustainable forest management is the process of managing permanent forest land to achieve one or more clearly specified objectives of management with regard to the production of a continuous flow of desired forest products and services without undue reduction of its inherent values and future productivity and without undue undesirable effects on the physical and social environment" (ITTO, 1992). Important activities involved in forest management include forest valuation, forest inventory and forest management planning, and yield regulation.

There is increasing awareness of the great value of forest for local people, and that they should profit from the various forest products in the first place. Socio economic aspects of forest management are considered very important at present.

Forest valuation

The procedure of determining the monetary and other value of a forest is called forest valuation. The value of forests is the sum of various products and services which fall into three major groups:

• Timber and non timber products from trees.
• Wildlife products and products from non woody plants.
• Intangible products and services expressed in terms of "forest influences" and "environmental value".

The value of a forest is often expressed in the value of the standing timber, known as the "stumpage value". It is based on the expected selling price of the timber products minus the estimated costs for production, profit and risk allowance (Buttrick, 1943). The approach for stumpage value appraisal is simple in principle, but the application has many complications because forest stands vary largely in terms of the size and quality of the timber produced. The valuation of forest on a sustained yield basis is much more difficult, and the contribution of non timber forest products and forest functions complicates the determination of the value even more.

Forest inventory and forest management planning

Forest inventory

Forest inventories can be conducted at various levels: per country (national forest inventory), in large forested areas (e.g. 100 000 ha) and in stands for the preparation of forest management plans. A most useful operation is a combination of partial inventories at the various levels (FAO, 1981):

• Reconnaissance of the forested area by photo interpretation (and some field plots) to estimate the areas covered by each forest type.
• Vegetation mapping of a selection of forest reserves (with complementary field plots) to roughly estimate the growing stock of each forest type.
• Detailed inventory of the most valuable forest areas.

The following inventory methods are implemented in Indonesia, and to varying degrees in other countries:

• Terrestrial inventory. This includes "reconnaissance surveys" which are low intensity inventories to provide rough estimates of forest condition for an assignment plan for concession holders; "management unit forest inventory" to provide more detailed information for long , medium and short term management plans and carried out by concession holders; "cruising" implemented by government forestry staff to check outcomes of the inventory by private concession holders; and "forest land use inventory" to provide information for better forest land use.
• Remote sensing techniques. This includes interpreting satellite imagery to obtain information on ground cover and forest classification; interpreting of small scale aerial photographs (1 : 100 000) to obtain information on existing land use, forest vegetation stratification and forest type classification; interpreting medium to large scale aerial photographs (e.g. 1 : 20 000) for more detailed information on forest types based on canopy structure, accessibility and land for non forest use; and ground check to revise the interpretation map and to construct volume tables.
• Volume tables. Volume tables are used to estimate stand volumes from aerial photographs (crown closure percentage and average stand heights). They are best applicable for pure stands and for forest of relatively homogeneous condition.
• National forest inventory. This country wide inventory includes monitoring of forest resources (forest cover types, assessment of changes) and an assessment of forest resources (forest stratification, growth and yield studies, construction of volume functions, compilation of results).

The national forest inventory of Indonesia started in 1988 and is scheduled to last 7 years. The first inventory in Peninsular Malaysia was carried out in 1970-1971, the second in 1981 1982, and the third was completed at the end of 1992. The first state wide forest inventory in Sabah was conducted in in 1969-1972. The current forest resource inventory in Sarawak is being done with the aid of aerial photographs of scale 1 : 25 000; in 1985 41% of the total forested land had been inventorized. In the Philippines, forest classes or strata are mapped into forest resources condition maps (of scale 1 : 50 000) with the help of aerial photographs.

The lack of "tree spotters" (persons who are able to recognize tree species in the forest by characteristics of buttresses, bark, cut or slash, exudates, fallen leaves, habitat, etc.) often hampers inventorying and controlling timber stands in the multi-species rain forest. The education and training of tree spotters should be an important part of forest inventory and management plans.

Forest management planning

Planning poses special problems in forestry because of the longevity of trees, the geographical extent of forest estates and the uncertainties of nature and market. The conventional planning tool in forestry is the forest management plan, which was largely developed in Germany in the 19th Century (Lanly, 1991). Forest management plans can be divided into three parts:

• General background and foundation material. This includes the purposes of management, accessibility to markets, social and economic considerations and general description of the forest. This kind of information does not change rapidly, is not a part of a specific action plan, and can best be prepared and applied to larger forest units.
• Specific information on the forest. Area, stocks, stand classification, condition, growth, cutting history and records, etc. The basic data consist of maps, cruise sheets and results of inventory, and the material is filed and kept current; it is the basic factual background.
• The plan proper. This is the action part, what is to be done. The key part is the regulatory framework determining the allowable cut by years or other periods of time, and the specific cutting budget for the period immediately ahead. The plan should also define action strategies regarding silvicultural and protection needs as directly relating to timber production, should correlate these with other uses, and provide for continuity.

There must be close links between those who prepare a forest management plan and those who are to administer it, and flexibility to meet the dynamics of a constantly changing situation.

Yield and yield regulation

The term "yield" in forestry is used in two ways. Firstly, it expresses the flow of forest products harvested from a forest at a particular time or during a particular period. Secondly, it is used to express the volume or amount of forest products that may be present in a stand at a given time, or attainable over a period of time, without reference to whether it is actually harvested or not. A yield table gives the volume of forest products (timber) that can be expected per unit of area for a given age, site, stocking, and method of management (Davis, 1966).

The actual yield of a timber plantation or natural timber stand is the timber volume per ha harvested by clear cutting or selective cutting when the rotation age has been reached. The yield can also be expressed on an annual basis (mean annual volume increment) by dividing the yield volume by the number of years of the rotation cycle. The eventual yield of thinnings can also be taken into consideration.

Clearly, the prime criterion for yield is increase in the volume of a forest. This differs considerably between natural and planted forest, different site conditions and species. For a mixed species tropical rain forest under good silvicultural management, a mean annual volume increment of bole timber of 8 m³/ha is considered very high, but plantations of conifers and eucalypts may reach an exceptional annual increment of 50 m³/ha. It should be realized that the actual annual volume increment (which can be estimated by girth or diameter increment and height growth) is not linear during the growth cycle. In general, the growth of trees follows a sigmoid curve with an initial slow phase followed by a phase of accelerating growth ("building phase"), finally slowing down and ultimately showing minimal growth ("mature phase").

Good yield regulation in natural forest requires the periodic removal of timber of mature trees, resulting in an equalization of the periodic yield. A balanced distribution of size or age classes is important to obtain sustainable yield, and good attuning of the yield to the forest condition is very important but difficult. In a certain area of production forest the yield can be controlled by dividing the total area by the number of years of the rotation to provide annual working areas. Differences in site quality can lead to adjustments of the size of the annual working area.

Socio-economic aspects of forest management

The need for agricultural land and demand for forest products is increasing with the fast growing populations in South East Asia. Conflicts of interest concerning forested land cannot be avoided, but eventually people are realizing that forests are indispensable for the community, economically as well as ecologically.

Foresters are increasingly acknowledging that more attention should be paid to the needs of indigenous populations in the forest and adjacent areas. This is manifested in new approaches to forest management and forest use, which can be generalized as "social forestry" or "community forestry", in which agroforestry practices are usually, but not always, included. "Social forestry is the science and art of growing trees and/or other vegetation on all land available for the purpose, in and outside traditional forest areas, and managing the existing forest with intimate involvement of the people and more or less integrated with other operations, resulting in a balanced and complementary land use with a view to provide a wide range of goods and services to individuals as well as the society" (Tiwari, 1983).

Social forestry aims to meet, at least partly, the basic needs of the local population, i.e. food, medicine, fuel, timber, rattan, fodder, income and a good environment. It often concerns the use of forest products in a non commercial manner, directly involving the beneficiaries concerned in the operations. In addition, it may also involve stimulating commercial forest utilization by local people instead of commercial logging enterprises, and stimulating the manufacture of forest products at village level. In these activities, attention is given not only to timber but also to non timber products. The forester has to assume another role than that of forest manager and guard, since there must be cooperation with local populations (Noronha, 1982). This new role calls for changes in forestry education. "If you want people to love the forest, first love the people" (Atmosoedaryo, 1978). Forestry agencies have abundant knowledge of timber stand management, soil and water conservation, and silviculture, but they have limited experience working with communities to manage forest lands (Poffenberger, 1990).

At present, social forestry principles are more and more systematically applied in forestry programmes. It is a participatory approach in sustainable forest management. Case studies for Indonesia, Malaysia, the Philippines and Thailand are briefly discussed below.

Indonesia

Programmes to control shifting cultivation were started in the early 1970s in an attempt to minimize adverse effects by introduction of economically promising perennial crops for degraded lands and better soil conservation techniques, provision of wage labour employment, and intensive extension and training. The programmes are implemented by various agencies such as the Ministries of Forestry, Agriculture, Transmigration, Social Affairs and Home Affairs. The total number of shifting cultivation households involved in the different programmes is approximately 125 000.

A social forestry programme was started in 1984 in Java, organized by Perum Perhutani (Government Forest Corporation) and supported by the Ford Foundation, with the following objectives (Bratamihardja, 1987): reforesting and restoring degraded forest lands, increasing the income of farmers living in the vicinity, and improving the relations between Perum Perhutani field staff and forest farmers. Important key activities are the establishment and development of forest farmer associations, and application of suitable agroforestry techniques.

Malaysia

An example of involving community development aspects in establishing industrial plantations is the programme of SAFODA (Sabah Forest Development Authority), concurrently promoting the establishment of forest settlements (Udarbe, 1987). The objectives of this programme are to convert wasteland and marginal agricultural land into productive forest land, to supplement the production of timber and non wood forest products from natural forests with products coming from man made forest, to encourage and promote active participation of the people in reforestation and afforestation, to provide mass employment, to raise the living standard of the people through forest settlement schemes, and to introduce forestry oriented land management practices. People from villages inside the forested area are offered permanent employment and accommodation in the plantation; their income is supplemented by agroforestry projects.

The Philippines

Shifting cultivation, locally known as "kaingin", accounts for at least 50% of total forest conversion in the Philippines. Other practices contributing to loss of forest are legal and illegal logging operations, forest fires and diseases and pests (Bayabos, 1988; Payuan, 1987). Until the early 1960s the response of the government to the problem of forest destruction was to prosecute shifting cultivators, but then there was a change of orientation towards community development, leading to the implementation of people oriented forestry programmes. In 1982 the Integrated Social Forestry Programme (ISFP) was launched; it aims to raise the socio economic conditions of forest occupants and communities and at the same time to help develop and conserve forest resources. Documents are issued by the Bureau of Forest Development to leaseholders, giving them the usufruct right of forest land, but committing them to conserve and protect the forest.

Thailand

Programmes which include logging permits for local wood cutters, intercropping in forest plantations (taungya system), allocation of woodlots as a source of fuelwood, integrated watershed development and voluntary tree planting programmes, were started in the early 20th Century and later consolidated in social forestry programmes in the Fifth National Economic and Social Development Plan (1982-1986). A programme for granting usufruct certificates was initiated in 1979. Under this programme the land is divided into two zones, the upper watershed area which is restricted and kept forested, and land that can be used for agriculture, which is granted to farmers under a certificate in areas not larger than 2.4 ha. The purpose of granting usufruct certificates is to give incentives to invest in the land, making it more productive, and to prevent further encroachment into forested land. In 1987 almost 100 villages were under the aegis of the forest village programme adopted by the Royal Forest Department (Pragtong, 1987).

Several socio-economic studies have examined the importance of forest utilization by rural people. An example is a study focusing on the socio economic conditions of logging crew workers in peat swamp areas (ramin (Gonystylus) forest) in Sarawak. It covers social and demographic aspects, income, consumption, health and working conditions (Ghani, 1987). Another example is a study in planted teak forest in Java focusing on the villagers living around the forests. Besides its protective function, teak forest plays an important role in providing the basic needs of people such as food, fuel, fodder and employment. Food is mainly produced through taungya. The volume of fuelwood collected per household ranges from 10-20 kg/day, and most of the fuelwood (70-100%) is extracted from the forest (Kartasubrata, 1990).

"Who are the rightful forest keepers" is becoming a major political question and an issue behind social conflicts (Poffenberger, 1990). The controversy between tribal versus legal/state ownership of forest should also be seen in terms of sustainable management. Forest communities of South East Asia possess a wealth of knowledge about how to sustainably manage forest lands to meet their needs. The practice of sustainable forest resources management, of which non timber forest product collection is an element, is a hallmark of the economy of traditional forest dwellers (de Beer & McDermott, 1989).

Silviculture

Silviculture is the branch of forestry dealing with the establishment, development, care and regeneration of stands of timber trees, with the aim of sustainably producing timber and other products and services. In fact, silvicultural practices and controlled harvesting techniques are parts of forest management.

Silvicultural systems in natural forest

A silvicultural system is a system of procedures and methods by which trees in the forest are harvested, regenerated and tended for sustainable production, resulting in the development of distinctive types of forest.

At present, there are three broad silvicultural systems which could be applied to natural forests in South East Asia (Tran, 1974; Soerianegara, 1976):

• The selective felling system. In this system all activities are carefully described and planned. It prescribes a diameter/girth limit, induction of natural regeneration, timber stand improvement and enrichment planting, reservation of trees for future harvest, a cutting cycle and a maximum annual allowable cut. Silvicultural systems of this type have been applied in the Philippines (Philippine selective logging system, PSLS), Indonesia (Indonesian selective felling system, TPI/TPTI), Malaysia (sustained yield selective felling system (SYSF), also referred to as selective management system (SMS) for hill dipterocarp forest, liberation thinning in Sarawak), Thailand (girth limit) and Vietnam (diameter/girth limit).
• The tropical shelterwood system. In this system several preparatory fellings are performed to improve the forest stand and promote natural regeneration, with the final felling being undertaken when natural reproduction has been established. This system was previously practised in Malaysia in lowland dipterocarp forest.
• The uniform system. This is essentially the tropical shelterwood system minus the preparatory fellings. The tree crop is harvested in a single operation if a prelogging inventory has shown that natural reproduction is satisfactory in terms of numbers and distribution. This system was applied in Malaysia for lowland dipterocarp forest (Malayan uniform system, MUS) and could be applied in Indonesia (clearfelling with natural regeneration, THPA).

Silvicultural procedures for natural forest management

Cutting of climbers and lianas liberates the crowns of trees. It is often necessary after serious interventions in natural forest (logging, thinning) because many species of lianas respond to improved light conditions by vigourous growth. The operation usually has to be repeated once or twice during the cutting cycle. During gradual transformation of natural forest (i.e. modifying the forest for economic reasons), undesirable trees must be removed by cutting (trees with small bole diameter) or by poisoning with arboricides (trees with large bole diameter). The arboricides used are often phytotoxic substances or synthetic growth hormones; phytohormones are considered less toxic to humans and animals. Thinning is sometimes necessary, depending on the silvicultural system used. It may promote regeneration and improve growth of young trees by allowing more light to penetrate the canopy.

Planting is sometimes practised in logged over natural forest. Trees are planted along cleared lines in the forest (conversion planting). Occasionally, planting in prepared openings or natural gaps is carried out to enrich natural forest (enrichment planting), usually using indigenous species.

Forest plantation systems

Poorly stocked natural forests and degraded land can be converted into timber tree plantations (forest plantations) by sowing or planting. This system is called clearfelling with replanting (artificial regeneration). Three types of forest plantation establishment are distinguished (FAO, 1976):

• Afforestation. The establishment of forest on land which previously (at least within 50 years) was not forested.
• Reforestation. The establishment of forest on land which was previously forested; it involves the replacement of tree species by other, more productive species.
• Artificial regeneration. The establishment of forest on previously forested land using essentially the same tree species as before.

The purposes of establishing forest plantations are manifold, not only for supplying raw materials for wood based industries (pulpwood, sawn timber, etc.), but also for providing fuelwood and charcoal, to establish or rehabilitate protection and amenity forests, and to conserve rare and endangered tree species. Fast growing species are usually preferred.

Silvicultural procedures for forest plantation systems

Species selection

Choosing the species to be planted in a plantation project is very important. The decision should depend on the purpose of the intended plantation, the species potentially available for planting, and the growing conditions of the sites.

If a plantation is planted for fuelwood or woodpulp, fast growth with early culmination of maximum growth rate is an important criterion for species selection. Large tree sizes are unimportant or even disadvantageous, and coppicing ability is desirable. For fuelwood the tree shape is unimportant, but for pulpwood straight stems facilitate rapid debarking. Wood properties are also important; the wood must dry quickly, have a low ash content, and burn steadily without smell and sparks (fuelwood), or have an appropriate fibre length, colour and extractives content (pulp wood). Examples of species chosen for large scale industrial plantations are Acacia auriculiformis, Acacia mangium (fuelwood, pulp), Anthocephalus chinensis (pulp), Eucalyptus spp. (pulp), Gmelina arborea (fuelwood and pulp), Leucaena leucocephala (fuelwood), Paraserianthes falcataria (pulp) and Pinus spp. (pulp).

Species planted in plantations for producing sawn timber or veneer/plywood must have moderate to fast growth and be able to grow to large size. A good form is important, with good natural pruning. For sawn timber the strength, seasoning and working properties, durability and preservation are important. For veneer/plywood the peeling quality, figure and bonding strength are important. Examples include dipterocarp species, Agathis spp., Swietenia macrophylla and Tectona grandis (all for sawn timber as well as veneer/plywood).

Most forest plantations are monocultures, but sometimes mixed plantations are established. In the latter case, the species should have similar purposes or end uses and rotation when planted in alternating lines, but this is not necessary when planted strip or block wise.

Propagation and planting

Growing seedlings in a forest nursery is the major method of raising planting stock. Obtaining adequate amounts of good seed is usually an important part of a plantation programme. The aim of seed collection is to obtain large quantities of seed of the best genetic quality. Sometimes seeds are collected from production plantations, but often from seed stands or seed orchards. They can be collected from the ground (e.g. teak, Gmelina arborea and several dipterocarps), but sometimes cones or fruits must be collected from the trees (e.g. Pinus, Araucaria and Swietenia species). The ability of seeds to remain viable varies greatly. Dipterocarp seeds usually have a short viability and can be stored for only comparatively short periods, but hard coated seeds of many legumes can be stored for several years without difficulty. Seed viability is usually prolonged by low temperature storage, by drying to low moisture content and by treatment with fungicides.

Methods of vegetative propagation are gaining importance as a way to maintain stock with superior characteristics obtained by breeding. Cuttings, air layering, budding and grafting are used to produce planting stock. Cuttings are most often used. The success depends on the stimulation of root formation and growth. Removal of leaves, the use of misting equipment (reducing transpiration stress) and the use of growth hormones may give better results. Planting stock produced by tissue culture is sometimes available, but this method is still in an experimental stage.

Tree seedlings are raised in the nursery either in an open bed from which they are lifted and planted with bare roots, or in individual containers which are taken to the planting site and planted with a clod around the roots.

Mycorrhizal inoculation of seedlings is often essential for good growth, e.g. for pines and dipterocarps. Adding soil from healthy stands to the potting mixture or the seed bed can give good results; another method is to grow mycorrhizal mother trees in the nursery bed. Techniques for the mass propagation of dipterocarps by shoot cuttings have been developed in the Tropenbos-Kalimantan project (Wanariset, East Kalimantan).

Often, seedlings are hardened off before planting into the field by reducing the amount of water.

The planting distance and the chosen thinning regime are among the most important silvicultural decisions. Spacing varies from 2 m × 2 m to 4.5 m × 4.5 m (5 m × 5 m or wider is usually confined to enrichment planting). Initial spacing depends on the desired product: for firewood and pulpwood the quantity of wood is of sole importance and close spacing is desirable; for sawn timber and veneer production wider spacings are desirable to obtain large log sizes, although spacing should be close enough to promote straight boles. Direct sowing into the field has been found reliable with only a few large seeded species such as Gmelina arborea, Swietenia macrophylla and Tectona grandis.

Weeding, thinning and pruning

Competition from weeds can cause seedlings to die. Selecting a weed free nursery site reduces the need for direct weed control. Chemical weed control is largely restricted to nurseries raising conifer seedlings because the chemicals kill seedlings of broad leaved species. Hand weeding is commonly practised. Nearly all plantations require some weeding during the first few years until the trees are approaching canopy closure. The removal of vines and creepers may be needed for many years.

Thinning usually starts 2 4 years after canopy closure. Thinning is practised to encourage crown development which results in bole diameter increment, to remove inferior trees and favour vigorous trees, and to provide an intermediate financial return from sale. The commonest form of selective thinning is removing trees in the lower canopy classes; it is largely a speeding up of natural thinning processes. The first thinning should be done before the live crown ratio (see Paragraph 1.4.4) is reduced too much (usually below 30 40%).

Pruning is done to produce knot free timber. It also gives easier access to timber stands and reduces the damage caused by fire. Several species show natural pruning, with dead branches falling off (e.g. pines and Anthocephalus chinensis). Artificial pruning is particularly important where wide spacing and heavy thinning are practised, and in plantations planted for the production of veneer/plywood and high grade timber. Branches are sawn off flush with the trunk, often using a specially curved saw. Pruning is usually done several times, with each successive cutting round somewhat higher, until the required length of pruned stem is reached. Pruning is often carried out in association with thinning; it is considered a value adding operation.

Fertilization

Fertilizers are used to establish plantations on infertile sites, and to promote optimal growth. Fertilizing at planting is most widely practised. Enrichment of soil nitrogen is also possible by interplanting with legumes such as Leucaena leucocephala. This is done in the Philippines to improve the growth of mahogany (Swietenia macrophylla), kadam (Anthocephalus chinensis) and teak (Tectona grandis).

Diseases and pests

Numerous organisms can harm trees. Monoculture plantations are particularly susceptible to diseases and pests.

In nurseries damping off diseases caused by fungi (especially Fusarium, Penicillium, Phytophthora, Pythium and Rhizoctonia) often occur. Seedlings die when tissue near the root collar rots, causing them to topple over. Nursery hygiene, quarantine measures, soil sterilization and adequate drainage of the soil can reduce the risk of damage, and direct control of damping off disease is possible with fungicides.

Fungi causing damage in plantations include Armillaria, Corticium and Ganoderma species, and sometimes the causal pathogens are bacteria (e.g. Pseudomonas) or viruses. In general, a particular insect problem is localized to certain nurseries or plantations and species. Defoliators and stem or shoot borers most commonly cause damage. Correct identification of the pest is important for appropriate control measures, but this is not always easy. Insecticides are generally used for direct control, but often other control measures are possible, such as biological control, switching to less susceptible tree species, and avoiding practices favourable to the organism (for instance, removing the waste wood from the forest floor after thinning may prevent insect pests from developing).

Forest fire

Fire is often an important danger facing a newly established plantation. Forest fire prevention includes establishing fire breaks along the forest boundary and between compartments, consisting of less flammable tree species or cleared ground, reducing the quantity of combustible materials on the forest floor, usually by controlled burning, and choosing less susceptible species. It is advantageous to make a forest fire prevention and suppression plan for each forest plantation unit and to use a fire danger rating system in relation to climatic conditions. It is essential to have an appropriate communication system. For successfully fighting forest fires, a sufficient quantity of water is needed and fire beaters and bulldozers are useful to make temporary breaks.

Felling and replanting

When a timber plantation has reached the rotation term (i.e. the planned number of years between planting and felling) it is clear cut and replanted. The rotation period depends on the species, the end use of the timber and the site quality. Good quality teak often needs a rotation of about 80 years. The rotation of fast growing species planted for pulpwood is usually only about 8 years. Site conditions for the second rotation are often different from those when afforestation began. Typical weeds of the first rotation have often been suppressed but there may be prodigous natural regeneration of the former crop, and stumps may produce coppice shoots. Of course, natural regeneration and coppicing can also be used to produce a second crop of the same species. However, the soil structure may have changed, making it necessary to use different silvicultural practices.

Timber harvesting and post harvest handling

Timber harvesting can be described as the felling of trees and extraction of usable tree parts (logs) from the forest. Its aim is to supply the timber market and wood processing industry with raw material. A number of logging techniques are typical for tropical forest exploitation. These techniques are adapted to the type of forest to be harvested: dry land rain forest, freshwater swamp forest, peat swamp forest, mangrove forest or plantation forest.

Nowadays the rain forests in South East Asia are largely logged using heavy mechanical equipment. Trees are felled with power saws and transported by crawler tractors or wheeled skidders towards forest roads or navigable rivers. In steep terrain, cable yarders such as the high lead logging system, are used to transport logs downhill. Further transport of logs to processing areas is carried out with heavy trucks and trailers along forest roads or rivers, on barges (pontoons) or as rafts. The actual harvesting process is characterized by a high degree of logging damage and waste of harvested timber.

In Indonesia, the Philippines and Malaysia efforts have been made in recent decades to bring the rain forest under regular management in order to guarantee sustained timber production while conserving the forest. The Indonesian selective felling and replanting system (TPTI) aims at limiting and controlling felling intensity and promoting regeneration through post harvesting treatment. The selective management system was developed in Malaysia to achieve sustained timber production through modern forest management. The Philippines introduced a system of controlled logging in 1953 for montane forest, which has to be harvested carefully to avoid erosion and land degradation. Although these logging and management systems are compulsory for concessioniares, they are difficult to implement, and control by national forest authorities is hampered by remoteness of logging areas, inadequate infrastructure, and lack of institutional staff and means of transport. Manual transport methods are used to harvest freshwater and peat swamp forests, or operations can be mechanized with the aid of light cable (yarding) and rail systems. A species such as ramin (Gonystylus bancanus) is regularly harvested in this way in Kalimantan and Sarawak.

End coating or S hooks may prevent logs from splitting and developing end checks. The logs of timber species which are very susceptible to fungal and insect attack should be treated with fungicides and/or insecticides soon after logging, or they should be extracted immediately from logging areas and processed rapidly. Examples of such timbers are kauri (Agathis spp.), pulai (Alstonia spp.), kadam (Anthocephalus chinensis), sesendok (Endospermum spp.) and ramin (Gonystylus spp.).

Plantation forests are becoming increasingly important for the timber supply in South East Asia. Not only the old established teak plantations in Java, but also other man made forests of fast growing tree species are beginning to play a significant role in meeting the demands for construction and industrial timber. These forests are harvested manually or with animal traction (in the Philippines buffaloes are used, in teak forests in Java cows and in Thailand elephants) but also with light skidders, agricultural tractors and cable yarders. Plantation forests offer better opportunities for sound logging and sustainable management, especially with regard to damage control and replanting.

Agroforestry and urban forestry

Trees and forests may serve other needs and functions than merely timber production. They are becoming increasingly important in integrated land use development, which involves integrating plantation forestry and agricultural land uses, and also planting and maintaining forest for recreational and aesthetic value.

Agroforestry

In 1989 ICRAF (International Commission for Research on Agroforestry) gave the following definition: "Agroforestry refers to land use systems in which trees or shrubs are grown in association with crops (agricultural crops or pastures) in a spatial arrangement or a rotation, and in which there are both ecological and economic interactions between the trees and other components of the system".

Many distinctive agroforestry systems can be distinguished on the basis of their components and their temporal and spatial arrangements; the most important main groups are:

• Systems with tree components predominating.
• Mainly agrosilvicultural systems (trees with crops).
• Mainly or partly silvopastoral systems (trees with pastures and livestock).

Agroforestry systems can be productive (food, fodder, fuelwood and also timber) as well as protective (e.g. soil conservation, soil fertility improvement, wind break and shelterbelt). They may also be classified using socio economic criteria, depending on production and level of management. Some agroforestry systems are very briefly discussed below.

The taungya system is practised on forest land. Tree seedlings are planted (with wider spacing than in normal plantations) at the same time or shortly after food crops. Food crops usually continue to be grown until canopy closure of the trees. In Java the taungya system is called "tumpangsari" and is particularly applied in the establishment of teak plantations (usually interplanted with Leucaena leucocephala), but also plantations of pines, Agathis spp., rasamala (Altingia excelsa) and mahogany (Swietenia macrophylla) in mountainous areas. The interplanted food crops include upland rice, maize, pepper, and in mountainous areas also cabbage, tomato, potato and onion. Important advantages of this system are the suppression of Imperata grass and the low establishment costs of forest plantations. A recent development is the intensification of cropping. Within the conventional system, farmers were allowed to intercrop for only 2 years, but in the new "full rotation agroforestry" system, intercropping spans the entire cycle of the forest stand (Bratamihardja, 1990). In Malaysia the taungya system is also practised; banana, maize and upland rice are planted between rows of teak, yemane (Gmelina arborea) and pines; cocoa and rattan between rows of rubber trees (Hamsawi, 1990). Bananas, sweet potatoes and taro are grown in Papua New Guinea for up to 3 years in newly established teak plantations, passion fruit in pine (Pinus patula) plantations in the highlands, and papaya, pumpkins and chillies in Araucaria plantations (Evans, 1982). Examples of agroforestry practised successfully in the Philippines include the combination of coffee and pines (Pinus kesiya) and plantations of Paraserianthes falcataria (for pulpwood) combined with small areas planted with agricultural crops (Lasco & Lasco, 1990). In Thailand the taungya system is integrated into the reforestation scheme of the rural development programme ("modified taungya system"), and there is multistorey mixed intercropping ("home gardens"). A multistorey agroforestry garden system having a forest like appearance is practised in western Sumatra, characterized by the integration of tree species from the forest and commercial crops.

Many other systems are applied in South East Asia, such as the improved fallow system with fast growing multipurpose trees, especially in shifting cultivation areas. The main objective of these systems is, however, not the production of timber, but the production of agricultural crops, non timber products, soil protection, grazing of livestock, etc., and the systems are often practised on a small scale. For more information on agroforestry systems, see the Prosea volume on auxiliary plants in agriculture and forestry.

Urban forestry

Trees are planted as a contribution to the well being of the urban population. They provide shade, give wind protection and intercept precipitation. Engineering uses of trees include erosion control and watershed protection, uses in wastewater management, noise and air pollution abatement, and glare and reflection control. The architectural and aesthetic uses are evident around buildings and parks (landscape architecture), and trees provide habitats for certain animals. Parks and forests in and near cities are important for recreation. Cities where urban forestry plays an important role include Singapore and Kuala Lumpur. The Prosea volume on ornamental plants deals with species and aspects of ornamental and roadside trees.

Forest and timber policy

Global

Forests are very important worldwide. Land classified as forest covers more than 4000 million hectares, or about one third of the earth's land surface. Of the total forested area, 58% is found in developing (mostly tropical) countries. The social and economic importance of natural and planted forests and trees for rural and urban communities and society as a whole is enormous. Forests provide industrial wood products, energy (fuelwood), food (e.g. fruits, meat), fodder, medicinal products, rubber, gums, resins, fibres etc. Forests are also extremely important ecologically, protecting land and water resources, storing and cycling nutrients, and providing habitats for wildlife. They have an important regulating function in maintaining the stability of the global biosphere in relation to carbon dioxide equilibrium. Forests constitute a rich stock of valuable genetic resources.

The concept of the word "forest" is often a source of confusion in discussions and figures about deforestation and afforestation. The term is used both for natural undisturbed forest and for plantations of fast growing tree species which often consist of exotics. The act of logging the natural forest and replacing it by industrial plantations of trees is called "deforestation", for instance, by persons connected with nature conservation, but often not by foresters. Forests subject to comparatively minor human interference such as selective logging, may already differ considerably from undisturbed forests. In fact, figures on deforestation should be interpreted carefully, as they give far from complete information about disturbance to the forest.

Causes of deforestation

It is estimated that an area of 17-20 million ha of forest disappears each year. Global re and afforestation required to counterbalance the losses is estimated to be at least 100 million ha. However, according to FAO figures, annual planting of new forests in the tropics was only 1.1 million ha at the end of the 1980s.

Global deforestation is the result of the following actions, in sequence of decreasing importance:

• Conversion into temporary farmland through shifting cultivation.
• Conversion into permanent farmland through large scale clearance.
• Cutting by rural populations for firewood.
• Clearance for large scale livestock farming.
• Destructive cutting for commercial exploitation of industrial timber.
• Construction of infrastructural facilities.

Conversion into farmland is by far the main cause of forest degradation; it is often estimated to be responsible for about 80% of deforestation. The direct responsibility of commercial logging for deforestation is comparatively small. The ultimate role of logging in global deforestation is often estimated as much greater since logging operations open the forest (e.g. by roads and other infrastructural facilities necessary for transporting the timber) and facilitate other human interferences. In fact, logging is of secondary importance when compared with other causes of deforestation which lie in complex socio economic factors. Rapid human population growth, poor economic development and neglect of rural areas outside the forests are the major influencing factors. Rural development towards sustainable agriculture in rainfed areas is of the utmost importance to create sufficient food production and employment for small farmers living next to the forest. Raising incomes and living conditions on a sustainable basis will relieve the pressure on forests. An alliance of forestry and agriculture is needed (Otto, 1990).

Rain forest and climate

The role of the rain forest for the absorption of carbon dioxide and the production of oxygen, and the influence of the percentage of these substances in the atmosphere, is difficult to quantify. The ratio of carbon dioxide absorption and oxygen production is more favourable in plantations of young, growing trees than in undisturbed rain forest which is in equilibrium. However, rain forests are considered to play an important role in climatic regulation. At the same time, the exact influence of the destruction of rain forest on the climate is not known. Climatic change tends to be attributed solely to the destruction of forest over large areas, and there is a tendency to neglect other causal factors. For instance, the irregularly recurrent droughts in Borneo which cause the death of many trees and increase the incidence of forest fires, are not of recent date, as is often assumed, but have been occurring for centuries. However, the waste wood left behind after logging makes the forest more liable to fire. Moreover, climate is most probably considerably influenced by volcanic eruptions and worldwide human and industrial pollution.

Global policy to protect the rain forest

In many timber importing countries environmental organizations lobby to restrict or even boycott the use of tropical timber and to use substitutes such as synthetic materials, metal or preserved timber of planted temperate species. It is argued that most tropical timber comes from forests which are not sustainably managed, and that restricting imports helps to slow down deforestation. Experts from international organizations such as the United Nations, the International Tropical Timber Organization (ITTO) and FAO have warned that restrictions to the import of tropical timber may be counterproductive, because they may eliminate a potentially important stimulus for conservation of forests. Moreover, an increasing amount of the timber is used domestically and does not enter international trade. The magnitude and gravity of the problem of tropical deforestation and land degradation has been acknowledged as one of the most serious threats to mankind in recent history. Without immediate action to resolve this crisis, more plants and animals will disappear, more watersheds be degraded, more valuable forest products be destroyed, and more people will suffer from the effects. It is extremely difficult to agree upon the best world policy concerning the exploitation and protection of tropical forest, but there is a general consensus about a number of important matters.

There is a tendency towards production forests which are managed and harvested in a sustainable way. Members of large organizations such as the ITTO have expressed the hope that, by the year 2000, all tropical timber will be obtained from forests managed sustainably. It is generally agreed that completely protected forest reserves of sufficient extent should be maintained or created to protect flora and fauna. A combination of logging operations and sufficient protection of endangered species is often only possible to a limited extent. Climax species (i.e. species characteristic for mature-phase natural forest) are poorly adapted to the nomadic existence imposed on them by logging cycles and are liable to extinction. Many countries have acknowledged the importance of the development and implementation of large scale programmes to afforest degraded land. Achieving greater land use integration by combining agriculture and forestry is a way to slow down deforestation and should be stimulated. However, the administrative difficulties in implementing such schemes and their complexity are daunting. Ultimately, the decision about world policy should be based upon a correct balance of all interests and functions of the forest. Weighing one against another is not easy and may differ per country and area. International cooperation is indispensable. One of the initiatives to build up international cooperation is the Tropical Forestry Action Plan (TFAP), coordinated by FAO and achieved with the help of the World Bank, the World Resources Institute and the United Nations Development Programme (FAO, 1985). The International Union for the Conservation of Nature and Natural Resources (IUCN) also plays a coordinating role through its forest conservation programme. Recently, the United Nations conference on environment and development in Rio de Janeiro (1992) produced the Rio Declaration and the Forest Principles, which call for enhancing a global partnership dedicated to the sustainable development of the world's forest resources.

Regional

The rate of deforestation in South East Asia (Vietnam, Thailand, Malaysia, Indonesia, the Philippines and Papua New Guinea) was approximately 1.7 million ha per year in the period 1985-1990 (Collins et al., 1991).

In general, a shift in forest and timber policy in South East Asia is noticeable. Logging is subjected to rules of varying strictness, reforestation is accentuated, and attempts are made to manage forests sustainably. Research is focusing on reforestation and species to be used for this purpose. Enrichment planting is one research topic and is already practised locally. Much research has already been done and lack of knowledge is no longer a barrier to action. The major obstacles are the lack of political and financial incentives to apply recommendations of researchers, and insufficient control of application of the rules. Since the 1970s, there has been greater cooperation among ASEAN countries (Brunei, Indonesia, Malaysia, the Philippines, Singapore, Thailand) through regional projects, seminars, workshops, training, exchange of forestry material and field travels. The 1981 Jakarta Consensus on ASEAN tropical forestry was an important result. It covers numerous major topics in forestry, but the declared policies have hardly been pursued in the individual countries.

In South East Asia there is a trend towards upgrading wood products within the log producing countries in order to raise the value of exported products. The export of logs is prohibited or limited by levies, and sometimes even the export of sawn timber and other semi manufactured wood products is restricted. Part of the money collected from levies is invested in the local wood processing industry and used for reforestation. Basic forestry policies are all geared principally towards sustained productivity, multiple use, maintainance of a healthy environment, the establishment of permanent forest estates, alleviation of poverty, equitable distribution of wealth and providing employment opportunities (Oliva, 1989). However, the priorities vary per country.

The governments of the major exporting countries (particularly Indonesia and Malaysia) object to the import boycotts on tropical timber proposed by environmental organizations in the industrialized western countries. The revenues are a prerequisite to finance general economic development.

National

Brunei

Since 1986 Brunei Darussalam has had a Forestry Master Plan. It allows forests to be managed to yield forest products for domestic consumption and for the expansion of forest industries. Moreover, it allocates forest areas for functions such as ensuring a sufficient and clean water supply, maintainance of soil fertility and minimization of soil erosion, conservation of nature and wildlife, education, research and recreation. There is not much pressure on Brunei's forest resources because of the high standard of living and the comparatively low population pressure. However, part of the natural forest is being converted to plantations to increase the timber production to meet future domestic consumption.

Indonesia

The Indonesian governments national forestry plan states that the following should be the principal objectives of forestry in Indonesia:

• Proper utilization of forest resources. Logging operations and wood processing should be intensified, and lesser known timbers should be utilized. New resources are established through reforestation.
• Development of nature conservation, by protecting areas and intensifying management of nature conservation programmes.
• Accumulating knowledge about the extent, potential and condition of forest resources by conducting a national forest inventory for the preparation of national plans and policy decisions.
• Ascertaining the definite status and suitability of forest land through land use planning.

All log exports were banned in 1985, but this was repealed in 1992; now high export taxes are applied.

The problem of long term land utilization in Indonesia is closely related to the population size and its uneven distribution between Java and the other islands. The transmigration programme necessitates opening up and converting forest land.

The reforestation and industrial forest plantation programmes consist mostly of planting fast growing species (pines, eucalypts, Acacia mangium, Paraserianthes falcataria) for pulp production and light timber for local use, apart from the teak plantations in Java.

Malaysia

Under the Malaysian constitution, land and forest are defined as the responsibility of the individual states and are thus within the jurisdiction of the respective states of Peninsular Malaysia, Sabah and Sarawak. Forest policy is formulated independently within each state. The National Forestry Council (NFC) was established in 1971 in order to facilitate the adoption of a coordinated and common approach to forestry. The NFC formulated a national forestry policy in 1978, of which the most important points are:

• Establishment of permanent forest estates and protection against destructive agents.
• Practice of sound forest management and encouragement of multiple use of forests.
• Promotion of integrated timber industries and efficient utilization, employment of modern scientific principles and appropriate technology, and upgrading of forestry research, education and training.
• Promotion of sound development of trade and commerce in forest products, and promotion of public awareness in the understanding of forestry.

Whereas the responsibility for timber production and forestry is mostly implemented at state level, conservation within Malaysia is both a state and a national issue. The pressure on natural forest because of logging is still high, particularly in Sabah and Sarawak. A reduction of the export of round logs from these states and more investment in local wood processing industry has started, and may slow down the rate of deforestation. Specific legislation protecting tree species is very limited. In Sarawak, Dipterocarpus oblongifolius has been declared a protected tree; other protected trees under Sarawak's Wildlife Protection Bill 1990 are six Shorea species (producing edible nuts) and both Koompassia species. Furthermore, belian (Eusideroxylon zwageri) may not be exported without special permission. In Peninsular Malaysia there is a total ban on the export of logs. However, the main way to protect individual timber species is by establishing completely protected areas.

Papua New Guinea

The total operable forest area of 15 million ha is currently being cleared very rapidly and there is urgent need for changes in the national forest policy. The new Forestry Act came into operation in June 1992. The objectives include:

• Protection of forest resources and environment.
• Maximum participation by natives in forest exploitation as a renewable resource.
• Best utilization of forests to achieve economic growth and employment creation.
• Encouragement of scientific study and research into forest resources to achieve sound ecological balance.
• Increased acquisition and dissemination of forestry oriented skills, knowledge and information through education and training.
• The pursuit of effective strategies for managing forest resources.

The new forest policy has two main objectives: firstly, to ensure the sustainability of the forest and, secondly, to harvest the forest in a way which will bring about economic growth, job creation and increased participation of native people in the forest and timber industries by more domestic processing.

Land and forests in Papua New Guinea are owned by the indigenous people by customary rights, unlike most countries in South East Asia where forests are state owned. The utilization of forest resources is subject to government control, and commercial harvesting and trade in forest products require a permit. Sustained yield management is the guiding principle for granting permits. Tree planting programmes such as timber plantation and woodlot establishment and agroforestry are encouraged. Ecologically important land is allocated for conservation purposes in agreement with traditional land owners.

Most of the timber harvested is still exported as logs (except conifers, Fagaceae, ebony (Diospyros spp.), kerosene wood (Cordia subcordata), teak, rosewood (Pterocarpus indicus) and black bean (Castanospermum australe), for which log exports are banned).

The Philippines

In the Philippines, where the reduction in forested land has been the greatest of all South East Asian countries in recent decades, the principal forestry legislation is the Forestry Reform Code, promulgated in 1975 by presidential decree. Its stated aims were as follows:

• The multiple use of forest lands shall be oriented to the development and progress requirement of the country, the advancement of science and technology and the public welfare.
• A land classification survey shall be systematized and hastened.
• The establishment of a wood processing industry shall be encouraged and rationalized.
• The protection, development and rehabilitation of forest lands shall be emphasized so as to ensure their continuity in productive condition.

The most recent developments and regulations regarding national forest and timber policy are:

• Reduction of timber operating licensees to reduce pressure on existing timber resources.
• A shift in the utilization and management of forest resources from private concessioniares to local communities. There is also a shift of implementation of reafforestation from the government to the private sector (communities, non governmental organizations, private individuals) on a contract basis.
• A total ban on commercial logging in all remaining virgin forests starting in 1992. In secondary forests, the smaller diameter timber should be utilized sustainably.
• In addition to a total ban on log export, there is a ban on cutting undersized trees (less than 60 cm diameter). Some tree species are completely protected (Pterocarpus indicus, Agathis philippinensis, Diospyros ferrea, Diospyros digyna).

Although regulations are very strict, there are major problems in controlling illegal cutting for timber and in limiting the destruction of forest by shifting cultivation.

Burma (Myanmar)

The forest policy in Burma was formulated already in 1894. Four main classes of forest were distinguished: protection forest, commercial forest, local supply forest and nature reserve forest. With slight modifications, this classification is still maintained today (San Maung, 1989). The present guidelines are to replace the logged areas with plantations, to increase the area of state controlled forest and to establish new areas of completely protected forest (nature reserves).

Thailand

Over the last 25 years, Thailand has lost about 45% of its forests (Oliva, 1989). In 1985 the National Forest Policy was formulated, with the objective to manage and develop forest resources on a continuing basis. At present, forest policy is geared more towards forest conservation and development, because of problems of deforestation. In January 1989 the Ministry of Agriculture and Cooperatives ordered a halt to all logging concessions.

Vietnam

Major aspects of the timber policy adopted by the Vietnamese government for the coming years are:

• A reorganization of the national forestry organizations.
• The establishment of a sound system of granting permits for timber harvesting.
• The strengthening of afforestation programmes in order to achieve an area of planted forest of 150 000 ha by 2005.
• The diminishing of export of unprocessed timber by imposing levies or by prohibiting the export.

Biodiversity, conservation and breeding

Biodiversity can be conserved at three levels: ecosystem, species and population. The forest formations described in Paragraph 1.5.3 can serve as a framework for the conservation of ecosystem diversity. A sufficient area of each formation should be conserved by being designated as nature reserves, taking into account that variation of individual formations may be large over the whole area, and therefore the conservation areas must be carefully chosen. In fact, very little is known about the size of area needed to conserve adequately populations of species, let alone complete ecosystems, and consequently conservation areas should, in principle, be large, since conserving adequate habitat is the underlying principle (Whitmore, 1984). Some types of forest are much more subject to logging or other human interferences than others, and are therefore disappearing more rapidly. Lowland evergreen rain forest, which is the most valuable kind of forest for logging and which is often first converted into agricultural land because of easy accessibility, is particularly vulnerable. Moreover, it needs special attention as it is the richest in species. Several national parks or nature reserves exist in name only and are not free from detrimental influences. Adequate control is sometimes difficult. It is difficult to conserve tree species as long as logging is done at trade group level and little attention is paid to inventorying stands of individual species. In addition, species vary over their area of distribution, and therefore the complete area must be considered when taking conservation measures, in order to maintain their genetic diversity. CITES (Convention on International Trade in Endangered Species of wild Fauna and Flora) can be invoked to protect species, although attempts to include commercially important timber species (e.g. Gonystylus spp. and Intsia spp. in South East Asia, Swietenia macrophylla in South America) have failed. However, control of trade in certain species is only possible if the product (timber) is recognizable and this seems impossible to achieve within trade groups which include numerous species.

In general, conservation of the genetic diversity of species should be realized in situ, but occasionally ex situ conservation can play an important role. Endangered trees should be planted in plantations or botanical gardens. Enrichment planting is usually restricted to commercially important species, but it could be extended by using endangered species as well.

The genetic diversity of a species is very important for breeding programmes. Natural stands of species are important sources of genetic material for tree improvement programmes which aim at improving characteristics (e.g. better wood quality, pest resistance) and productivity. The use of suitable provenances, adapted to certain environmental conditions, is a first prerequisite for a successful programme. There are two main phases: the operational and the developmental. The objective of the operational phase is to produce seeds for planting, the developmental phase should provide a long term, broad genetic base for continued breeding programmes.

Forest tree improvement encompasses the following activities:

• Investigating the variation in populations of tree species.
• Conducting provenance trials.
• Selecting and multiplying trees possessing desired characteristics.
• Storing the desired characteristics in a seed orchard.
• Crossing selected trees to obtain offspring possessing a combination of desired characteristics (breeding).
• Conducting progeny tests in plantations.

Supporting activities include studies on phenology, the biology of flowering and fruiting, breeding systems, cytogenetics, and vegetative propagation. Tissue culture has given new impetus in forest tree improvement.

Forestry research in South East Asia

Main research topics

Research priorities in South East Asia are (Salleh, 1992):

• Forestry in relation to agriculture and rural development.
• Forestry in relation to energy production and use.
• Management and conservation of the natural tropical rain forests.
• Utilization, including value added processing, of lesser known species and of agricultural residues.
• Multiple use and resources of non timber forest products.
• Environmental forestry including watershed and hydrology.
• Policy and socio-economics.

Main institutions

The main institutes and universities conducting forest research or engaged in forest products in the respective countries of South East Asia are:

Indonesia

• Centre for International Forestry Research (CIFOR), Bogor
• Centre for Rehabilitation of the Tropical Rainforest, Samarinda
• Forest Products Research and Development Centre, Bogor
• Forest Research and Development Centre, Bogor
• Forestry Research Institute, Kupong
• Forestry Research Institute, Manokwari
• Forestry Research Institute, Pematang Siantar
• Forestry Research Institute, Samarinda
• Forestry Research Institute, Ujung Pandang
• Institut Pertanian Bogor, Bogor
• Institute for Reforestation Technology, Banjarbaru
• Institute for Reforestation Technology, Palembang
• Pusat Penelitian dan Pengembangan Biologi, LIPI, Bogor
• SEAMEO, Regional Centre for Tropical Biology (BIOTROP), Bogor
• Tropenbos-Kalimantan, Wanariset I Samboja Research Station, East Kalimantan
• Universitas Gadjah Mada, Yogyakarta
• Universitas Hasanuddin, Ujung Pandang
• Universitas Lambung Mangkurat, Banjarmasin
• Universitas Mulawarman, Samarinda
• Universitas Pandjadjaran, Bandung
• Universitas Tanjungpura, Pontianak

Malaysia

• ASEAN Institute of Forest Management, Kuala Lumpur
• ASEAN Timber Technology Centre, Kuala Lumpur
• Forest Research Institute Malaysia (FRIM), Kepong
• Malaysian Timber Industry Board, Kuala Lumpur
• Malaysian Timber Industry Development Council, Kuala Lumpur
• MARA Institute of Technology, Shah Alam
• Sarawak Timber Industry Development Corporation, Sarawak
• State Forestry Department, Sabah
• State Forestry Department, Sarawak
• Universiti Pertanian Malaysia, Serdang
• Universiti Sains Malaysia, Penang

Papua New Guinea

• Forest Management Research Branch, Port Moresby
• Forest Products Research Centre, Port Moresby
• Forestry College, Bulolo
• Papua New Guinea Forest Research Institute, Lae
• Timber Industry Training College, Lae
• University of Technology, Lae

The Philippines

• Ecosystem Research and Development Bureau (ERDB), Los Baños
• Forest Products Research and Development Institute, Los Baños
• Philippine Council for Agriculture, Forestry and Natural Resources Research and Development (PCARRD), Los Baños
• Don Mariano Marcos Memorial State University, Batac
• Ifugao State College of Agriculture
• Isabela State University, Echague
• Mindanao State University
• Tarlac College of Agriculture
• University of the Philippines, Los Baños
• Visayas State College of Agriculture, Baybay

Burma (Myanmar)

• Forestry Research Institute, Yezin

Laos

• Forestry College, Vientiane

Thailand

• Royal Forest Department, Bangkok
• Kasetsart University, Bangkok

Vietnam

• Forestry Research Institute of Vietnam, Hanoi
• Tropical Forest Research Centre, Hanoi
• Forestry College, Xuan Mai

Prospects

The anti-tropical timber campaigns in Europe and the United States, notwithstanding the scientifically weak position of several arguments (such as global warming), influence political and economic decisions in those countries, and will affect the international market potential of the South East Asian hardwood timbers. Sustainable management of natural production forests and production of timber in plantations will eliminate the objections to using tropical hardwood. The International Tropical Timber Organization (ITTO, 1990) has expressed the hope that all tropical timber entering the international market will originate from sustainably managed forests or timber plantations by the year 2000. This will require an adequate system of labelling the timber obtained from sustainably managed forest. More efforts should be made to bring the forests of South East Asia under a system of scientific forest management and controlled timber harvesting. As well as improving harvesting regulations, the forestry institutions should also be strengthened to perform their tasks of guarding and protecting the forest, and of guiding the loggers.

Undoubtedly, natural forests can be managed in a sustainable manner to produce a variety of high quality hardwoods, but the felling systems, cutting cycles, and silvicultural practices such as enrichment planting need to be very carefully attuned to the type and conditions of the forest concerned. Much is known about harvesting and silvicultural practices, but they need further improvement through research. Dissemination of knowledge should be improved by education, training and extension, and aimed at forestry personnel as well as small farmers. To achieve sustainable management, timber extraction will have to be reduced in many forests. The prices of timber and wood products can be expected to increase considerably, which may make metal and synthetic materials more important as substitutes (e.g. for window frames) and wood more a luxury article on the international market.

The significance of forests goes far beyond their yield of timber. The functions of forests include such essential ones as climatic regulation, protection of environment and conservation of biodiversity. These functions are essential for life on earth and cannot be expressed in economic values. There is increasing recognition of the value of non timber products of the forest such as rattans, bamboos, medicines, edible fruits and game. To maintain the full genetic diversity of plant and animal species, sufficient and representative samples of tropical rain forest must be permanently conserved. However, it is unreasonable to expect countries to conserve more than a small proportion of their forested land area as protected national parks, despite the increasing benefits from tourism. Comprehensive financial support from industrialized countries is indispensable.

The establishment of timber plantations can greatly contribute to timber production, but should be integrated in land use programmes including agriculture. Timber production will be increasingly important in agroforestry systems. Modern breeding and propagation techniques can contribute to develop strains of plantation trees that are superior in productivity, wood quality and resistance to diseases and pests.

National forestry research organizations should be strengthened through financial support, training opportunities and links to institutions within and outside the region. The linkage can best be realized through networking mechanisms (Salleh, 1992).

In conclusion, it seems realistic to expect that in the future a reasonable level of timber production can be combined with decent forest protection, provided there is good collaboration between countries and disciplines, and all parties are prepared to make concessions. The integration of forestry in agricultural programmes and the execution of large scale afforestation programmes will be important. Far reaching decisions on timber policy and their implementation must not be postponed any longer, because time is running out.

Authors

I. Soerianegara & R.H.M.J. Lemmens

with contributions from

• P. Baas (wood anatomy),
• J. Hendrison (timber harvesting and post harvesting handling),
• J. Kartasubrata (forest management, agroforestry and urban forestry),
• S.I. Wiselius (properties) &
• W.C. Wong (wood processing)