Flowering and fruiting phenology of a Philippine submontane rain forest: climatic factors as proximate and ultimate causes

1 Phenological patterns of flowering and fruiting are presented for 5800 trees of a Philippine submontane forest community during a 4-year period. Circular vector algebra allowed species to be grouped into annual (34 species), supra-annual (3), irregular (7), and continuous (13) reproducers. 2 Wind- and gravity-dispersed species had extended fruiting periods coinciding with the typhoon season (July to November), whereas fleshy fruited trees showed peaks matching those of solar irradiance. Most species flowered at the beginning and fruited at the end of the first peak (April), or they flowered during the first peak and fruited during the second peak (September), indicating that solar irradiance may be a strong selective factor in shaping community-wide phenology patterns. 3 An El Nino and a La Nina climate anomaly occurred during the study period. Principal component analysis showed that 95% of intraspecific variation of flowering and fruiting dates could be explained by delayed or advanced flowering and fruiting of a limited number of species. Mast-fruiting of dipterocarp species could not be correlated with El Nino and La Nina events.<LF> <LF>4 Large climate-induced variation in phenology was demonstrated for the percentage of trees that reproduce, while the timing of phenology remained unaffected for most species, suggesting that climatic factors are not directly responsible for triggering and synchronization of phenological events.