Seasonal and interannual fluctuations in global climate are key regulators of reproduction in tropical forests. Global climate phenomenon such as El Niño Southern Oscillation (ENSO) are known to play an important role in regulating interannaul variation in reproduction, as do severe storms such as hurricanes. Using trap-based phenology data collected fortnightly from 1993 to 2013 from a hurricane-affected (1989 Hugo, 1998 Georges) subtropical wet forest site in northeastern Puerto Rico, we conducted a time series analysis of flowering and seed production. We addressed 1) whether reproduction (number of species flowering or fruiting) was seasonal in this “everwet” (zero months averaging precipitation < 200mm) site; 2) the degree to which interannual variation in flower and seed production was influenced by global climate drivers and time since hurricane disturbance; and 3) how long-term trends in reproduction varied with plant lifeform.
Results/Conclusions
A Seasonal-Trend Decomposition analysis revealed that flowering and fruiting were seasonal in our everwet site, confirming an earlier analysis using only the first 10 years of data. The seasonally de-trended number of species in flower fluctuated over time with no long-term trend while the number of species producing seed fluctuated around a declining trend, one that was particularly evident during the second half of the study period. Lagged correlation analyses indicated these patterns were influenced by Pacific-focused El Niño climate indices as well as Atlantic-oriented indices, suggesting complex global influences on tropical forest reproduction with variable periodicities. Lag times affecting flowering tended to be longer than those affecting fruiting. Long-term patterns of reproduction in individual lifeforms paralleled the community-wide patterns, with large trees and shrubs exhibiting more sensitivity to hurricane disturbances than small or medium trees. There was no long-term increase in liana or vine reproduction as reported in other neotropical sites.