Long-term fluctuation of biological activities in a lowland dipterocarp forest : Does general flowering contribute to maintenance of biodiversity

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General flowering, one of the most spectacular and mysterious phenomena in tropical biology, is a masting phenomenon unique to Asian dipterocarp forests. It is unique in involving the synchronization of flowering thus fruiting across diverse plant groups. GF occurs at irregular intervals of less than 1 year to several years. We showed that this phenomenon was most likely triggered by irregular droughts based on 10 years of observations. In the aseasonal forests of SE Asia, droughts tend to occur during transition periods from La Nina to El Nino, which results in an irregular 6-7-yr cycle involving a dry period with several droughts and a wet period without droughts. On the other hand, reproductive success was positively correlated with the magnitude of general flowering. We have aim monitored population dynamics of various insects and small mammals, which are likely to be affected by general flowering. Leaf beetles collected by light traps showed various fluctuation patterns depending on species, but species sharply corresponding general flowering were very rare Therefore, we consider that general flowering is not the major driving forces of fluctuation of populations of leaf beetles. Possibly, leaf flushing may explain part of the patterns. On the other hand, population fluctuation of terrestrial and arboreal small mammals largely followed flowering and fruiting patterns. Abundance of young individuals were larger just after flowering event, thus they may depending on general flowering for reproduction. Since they are considered to be predators of dipterocarp seeds, synchronized fruiting may contribute reduction of seed predation by such mammal species.