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[Anual Report 96 :
Table of Contents]

Rehabilitation of
Degraded Tropical Forest Ecosystems

Almost 17 million hectares of tropical forests are cleared for agriculture annually, while a further 5 million hectares become secondary forests after timber harvesting. Detailed knowledge of the long-term impacts of tree harvesting on forest ecosystems, especially changes in vegetation, soil and productivity, is still lacking. Assessing the impacts of logging and burning through long-term monitoring over a range of conditions (e.g., the time and methods of logging, transport, species removed, soil characteristics, topography and rainfall), will provide the scientific basis for minimising site damage and facilitating ecological restoration.

Rehabilitation of degraded forests and lands is urgent. In logged-over forests, where former ecosystems remain more or less intact, methods to accelerate natural regeneration are needed. Where ecosystem functioning has been disturbed, plantations provide an option. However, the success of regeneration or reforestation depends on accurate evaluation of site conditions after logging. Analyses of biological and physiological characteristics of regenerated or newly planted trees ­ and of the processes influencing productivity ­ are necessary if rehabilitation and reforestation activities are to succeed.

Short-rotation plantations cause changes in nutrient storage and cycling processes due to changes in erosion, leaching and patterns of organic matter turnover. All of these affect the sustainability of plantations, but opportunities exist to manipulate them through silvicultural practices. The challenge for researchers is to provide the scientific information to devise silvicultural systems which enhance soil properties important to sustainable production, and minimise deleterious effects. These practices must not only be technically feasible and economically viable but also socially acceptable.

In consultation with scientists at the Forestry and Forest Products Research Institute at Tsukuba, Japan, a framework for research has been prepared. During 1995-96, research partners were identified and a set of inter-related research activities developed. The research is being managed by Dr Shigeo Kobayashi, based in Bogor, and conducted in collaboration with a network of scientists in Indonesia and Peru. Additional work is taken place in Malaysia, Papua New Guinea, Brazil, Thailand and Argentina. This research complements and reinforces other CIFOR research on the sustainable management of natural forests and plantations, and conservation of genetic resources and the environment by addressing:

• Evaluation of the impacts of forest harvesting on forest ecosystem functions;
• Development of methods to rehabilitate logged-over forests and degraded forest lands; and
• Development of silvicultural techniques on degraded forest lands (site management and productivity in tropical forest plantations).

This collaborative research is generously supported by the Ministry of Foreign Affairs through the Ministry of Agriculture, Forestry and Fisheries, Japan.

Shigeo Kobayashi