Proximate cues of flowering in a subtropical rain forest

Plants have evolved mechanisms to track seasonal variation in environmental resources, enabling them to time key life-history events to appropriate seasons. While the proximate cues for flowering initiation are well documented in the temperate region, it is still unclear what the flowering cues are in the tropics, especially in the subtropics. Our study compared first flowering dates (FFDs) predicted by eight hypothesized proximate cues concerning photoperiod, mean and directional changes in solar irradiance and warm/cool temperature, and rainfall with flowering dates observed over 19 years of weekly monitoring for 16 species in a subtropical rainforest. We observed considerable inter-annual variation in the median FFDs for the study species, ranging from 21 to 101 days. The early-spring flowering species tended to have greater inter-annual variation in FFDs than the summer flowering species. For 13 study species, temperature cues best explained inter-annual variation in FFDs. Cool temp...