Introduction de la bionomie dans la gestion des forets tropicales denses humides

- INTRODUCTION OF BIONOMICS IN TROPICAL RAIN FOREST MANAGEMENT -Conservation of tropical rain forests as renewable resources is governed by the bionomics of the forest ecosystem. Bionomics are here used as the set of conditions that govern the development and existence of an organism, species or biological system in a changing environment. These "life rules" should be considered to represent thresholds to the kinds of use that can be made of natural biological systems without endangering the further existence of its composite species.Studies of the thresholds in sustainable use of tropical rain forest have been conducted in the Ivory Coast. An undisturbed relict of the West-African rain forest belt, preserved in Taï National Park, provides possibilities to study natural processes of forest dynamics and diversity. The main focus was on occurring variations in forest composition, matrix and architecture along slopes in the undulating landscape. Further studies were made of forest dynamics through the occurring patterns in tree mortality and the conspicuous ageing and die-back features of canopy trees. Data on forest composition and dynamics were collected in two forest plots, one of 7 hectares established in 1977, covering a gentle slope in the middle of a watershed of a first order tributary of the Cavally River, and another of 10 hectares, established in 1981, on a steeper slope near the border of the same basin.A more detailed study is reported on the ageing and die-back processes that occur in two characteristic canopy tree species. Crown development sequences were therefore established for the species Piptadeniastrum africanum and Pycnanthus angolensis. The die-back patterns in individual tree crowns are discussed in relation to possible changes in their physiological state. Large-scale aerial photographs of these two tree species were made and showed the possibilities for reconnaissance of the described ageing features in aerial surveys. In the end conclusion is stated what the possibilities are for the introduction of a bionomical approach in conservation oriented management of tropical rain forests as restrictively used, low yielding timber resources. Therefore, the principal rules that have appeared in the reported studies on forest composition, architecture and dynamics are summarised and the possibilities are discussed of the reconnaissance of senescent trees in aerial surveys and by field observations.