Silviculture management of natural dipterocarp forests - the rehabilitation of logged-over forests

When degradation of mixed dipterocarp forest ecosystem occurs, this is indicated by the loss of biological diversity that involves the dipterocarp species, reduced commercial value of the wood and wood products, decreasing quality and quantity of non-timber forest products, decreasing forest ecosystem functions and loss in fertility of the soil. Anthropological impacts and conflicts, such as population increase, inappropriate land utilization and conflict among land utilizations, are some of the main causes for these phenomena. We fully recognize such degradation in secondary forest, logged-over forest burnt forest, etc. Therefore, the rehabilitation of degraded mixed dipterocarp forest ecosystems is technically and socioeconomically important. This paper therefore focuses on the ecological and physiological characteristics of dipterocarp seedlings, clarifies and evaluates the logging impacts which include secondary succession after harvesting and approaches to improve the value of such secondary, logged-over and burnt dipterocarp forests. Forest structures and some ecological and physiological characteristics of dipterocarp seedlings are also discussed with respect to (1) forest structures of Shorea albida stands compared with Agathis forest and mixed dipterocarp forest, (2) energy (assimilated resources) allocation patterns of some seedlings in different forests, (3) mortality and growth of S. albida seedlings at different site conditions, (4) regeneration process after harvesting of S. albida stands and seedling establishment, (5) adaptive strategy of the energy (assimilated resources) allocation to the seedling population establishment, and (6) natural regeneration potential at the present situation. Logging impacts and secondary succession after harvesting are also clarified on (1) selective cutting and yarding, (2) changes in forest structure, (3) changes in microclimate and soil, and (4) vegetation recovery and secondary succession. Rehabilitation and improvement of the value of the secondary, logged-over and burnt dipterocarp forests would include accelerating natural regeneration and enrichment planting. The paper also looks at how to contribute to the sustainable forest management and conservation of environment as the final goal of this study. It is important to consider not only technical synthesis, but also socio-economic aspects such as local community participation and socio-economic acceptability. Information on natural secondary succession process will also contribute to developing these techniques. Increasing rehabilitatcd mixed dipterocarp forest will contribute to the area of potential sites for forested lands under limited land resources. the sustainable use of dipterocarp forest resources and the conservation of primary mixed dipterocarp forests and environmental improvement.