Plant reproductive phenology in tropical forests : Implications of general flowering in a lowland dipterocarp forest.

Abstract

General flowering (GF) is a phenomenon unique to lowland dipterocarp forests in Southeast Asia. During GF, which occurs at irregular intervals of 3-10 years, most dipterocarp species, together with species of other families, come heavily into flower sequentially for several months with high intraspecific synchronization. A series of studies conducted in Lambir Hills National Park, Sarawak, Malaysia, by the Canopy Biology Program in Sarawak (CBPS) have described the phenomenon and plant-animal interactions of GF in detail. They showed that fluctuations of available flower and fruit resources caused by GF had great effects on animals, and possibly contribute maintenance of species diversity in the forests. In the light of these findings, it was suggested that predator satiation proposed by JANZEN (1974) alone could not explain GF, and that two other factors-promotion of pollination and paucity of climatic cues suitable for flowering trigger-might be involved. GF also has some implications for phenological studies in tropical forests. The supra-annual seasonality of GF indicates that the complicated nature of phenology in tropical forests requires suitable methods of description. One of the most useful indices may be the flowering frequency of an individual plant. In addition, integrative studies at a particular field site and comparison of phenology and other biotic and abiotic factors among tropical forests are essential. Although phenology comparisons among different forests are often difficult due to differences in methodology, are now underway to integrate different phenological studies.