Narrow Results

A series of growth experiments and observations on natural populations have been carried out on dipterocarp species of contrasting ecology growing in artificial gaps and the forest understorey. These studies have demonstrated that although differences exist between species in photosynthetic and growth responses to the high-light environment, competition for light in canopy gaps is highly asymmetrical and tends to reinforce any pre-existing dominance hierarchy. We propose that differences in seedling persistence in forest canopy shade are highly influenced by species-specific biotic and abiotic interactions. Our experiments suggest that as seedlings, dipterocarp species trade off traits which enhance persistence and growth in shade against those that enhance their ability to exploit gaps. Less competitive species survive for progressively longer periods of time after a gregarious fruiting event. This leads to significant shifts with time in the number of species present in the seedling bank and hence in the importance of interspecific competition in determining which species dominates regrowth in gaps. We propose that this special case of dispersal limitation is more likely to account for coexistence of dipterocarp species than differences in growth responses to gaps of different size, with stochastic and environmental variables interacting to determine species distribution and abundance.

Abundant charcoal in forest soils gives evidence of prehistoric and historic natural and anthropogenic wildfires in perhumid lowland and in seasonal Dipterocarp forest types of continental and insular South Asia. Favourable conditions for the occurrence of historic and contemporary rain forest fires are associated with cyclic droughts caused by the El Niño-Southern Oscillation [ENSO] event. The escalating pressure of wildfires on the Dipterocarp forest biome originates from swidden agriculture systems and forest conversion programs. A detailed study of the ecological consequences of the wildfires of 1982–83 was conducted on an area of 2.7 × 10⁶ha of rain forest in East Kalimantan. The results show that Dipterocarps are very susceptible to fire and are replaced by pioneer and fire-tolerant species which occupy the disturbed sites or survive the immediate fire effects. Smoke from forest conversion burning causes considerable environmental problems reducing visibility, and affecting human health. In addition, emissions from forest fires may even influence the atmospheric chemistry on a global scale.

It is estimated that there are 70 million hectares of forest requiring rehabilitation in the Asia-Pacific region. Heavily disturbed and abandoned shifting cultivation areas need to be replanted, which consequently will require huge amounts of seedlings. Production of dipterocarp planting stock has been considered somewhat difficult. Seed availability and storage are continuous problems in mass production of dipterocarp seedlings. There is a lack of reliable knowledge of basic nursery operations because of the large number of species, the recalcitrant seed and contradictory information from different areas. Planting stock of dipterocarps can be produced from seed, wildlings and vegetatively by cuttings. Containerized seedlings or wildlings grown in mixtures of peat and ricehusk or topsoil provide the most reliable solutions at the moment. Vegetative propagation has had promising results recently and it is increasingly used on a practical scale. Reliable mycorrhizae inoculation is one of the key issues in successful seedling production. Pest and disease problems have to be considered more carefully if dipterocarps are used in large-scale plantations. Strict quality control of the planting stock is necessary. Production of dipterocarp seedlings is more expensive than seedling production of fast-growing trees, but investment in proper nursery practices is necessary. For large-scale plantation programmes, seedling production by combining all of the available methods (seeds, wildlings, cuttings) seems to be the most appropriate strategy. A strong emphasis on continued research and development activities is recommended. More knowledge is needed, but this fact should not prevent anyone from starting to plant dipterocarps.

Based on observations in the experimental dipterocarp plantations of the Forest Research Institute Malaysia and on research of more than 60 years the experience with planting dipterocarps in Peninsular Malaysia is summarized. Planting history, silvics and species choice, planting stock production, plantation establishment and tending and economics are discussed. Suggestions for a generalized stand management regime are presented.

Log landings and skid trails made by bulldozers during logging operations recover much more slowly than adjacent areas which were not traversed by heavy machinery. Even decades after completion of logging operations the vegetation on such areas is sparse with few or no tree species. Where logging is unplanned, log landings and skid trails can cover up to 40% of the total forest area resulting in a loss of productive forest. Therefore, artificial rehabilitation may be needed for such sites. A major constraint to both natural and artificial recovery is the poor physical and chemical properties of the soils on log landings and skid trails. Repeated use by heavy machinery results in severe soil compaction which leads to poor root development, low water availability and high rates of erosion. In addition, most of the topsoil is removed from log landings and skid trails by bulldozers during logging operations. A very high proportion of nutrients are found in the top few centimetres of rainforest soil, so removal of the topsoil exposes the very infertile subsoil. Despite these adverse conditions, it has been shown that some seedlings of some dipterocarp species can survive and grow on log landings if soil amelioration treatments are used. The various techniques available for planting and subsequent maintenance are discussed. The cost of rehabilitation ranges between approximately US$ 1,000 and US$ 1,500 per hectare.

An increase in world population and per capita income has generated unprecedented demands for fiber-based products. Consequently, wood production from timber-producing countries of the Pacific Rim has dramatically increased in recent years. Several countries in Southeast Asia have vast timber resources, primarily from the Dipterocarp forests which reach optimum condition in the evergreen rainforests of Peninsular Malaysia, Sumatra, Borneo, and the Philippines. At the same time, harvesting intensity has caused considerable degradation of the environment and depletion of forest resources, to such an extent that the problems are of great concern to many people. This paper discusses the forest resources of the Pacific Rim as they affect international trade. Indonesia is now the largest timber producer in the region; therefore, special emphasis is placed on the development of its forest products industries and the impact of environmental issues on forest conservation and management. Because the bulk of tropical timbers comes from Dipterocarp ecosystems, which also contain most of the presently underutilized species, their known wood properties and utilization potential are described. Alternative markets for wood use and new technologies to improve the effective utilization of wood are presented.

Dipterocarpaceae is the economically most important family in the forests of Indomalesia, producing more timber than the trees of all other families combined. With very few exceptions, Dipterocarpaceae are medium-sized or large to very large trees, and their economic value depends on the many useful kinds of timber they produce. The occurrence of vertical intercellular (resin) canals in combination with tyloses is the best diagnostic character set of South-East Asian Dipterocarpaceae. Structural differentiation within the family is sufficient for delimiting groups or genera. Biological, physical, and strength as well as working properties extend over a wide range to qualify the great majority of dipterocarp timbers for general utility purposes, yet only very few can be properly classified as 'special-purpose' woods. Lacking the specific attractiveness of typical fancy woods, dipterocarp timbers owe their very success in the market mainly to such factors as availability of large dimensions and volumes, continuity of supply, wide range of technical applications, skillfull marketing concepts, and a very favourable relation between cost and performance in service.

About 15 species of the Dipterocarpaceae family, mainly of the genus Shorea, produce a nut with an edible fat, identical to that of cocoa, and an excellent substitute for cocoa butter in the manufacture of chocolate and cosmetics. Since the trees also produce an excellent timber, logging operations threaten these species. Therefore, new approaches intend to establish smallholder plantations for the production of Tengkawang nuts and timber in Kalimantan. Possibilities and constraints of Tengkawang cultivation are discussed in this paper.