The impact of El Nino on mast fruiting in Sumatra and elsewhere in Malesia

Long-term data on Bower and fruit production of the forest community in two lowland tropical rain forests in north-western Sumatra are presented. The proportion of years with mast fruiting was found to be similar to that foun d elsewhere in Malesia. However, masting at the two sites, 70 km apart, did not coincide, and showed no correlation with the El Nino-Southern Oscillat ion phenomenon (ENSO). Comparisons with other sites in Malesia suggest a ge neral waning of ENSO's impact toward western Malesia. Spatial variation at various scales in the timing of masting events was noted in Sumatra and els ewhere. This suggests that additional factors to ENSO play a role in determ ining forest-level mast fruiting, and we hypothesize that frugivorous anima ls have the opportunity to track mast fruiting. It is hypothesized that asy nchrony between nearby areas in masting increases toward the western edge o f Malesia.