Shifts in plant phenology are one of the most compelling indicators that species are responding to climate change. Although cerrado, the seasonal neotropical savanna, is one of the world’s biodiversity hotspots, its long-term phenology and related environmental triggers are still not understood. Here we present our unique 12-yr data set on cerrado reproductive phenology, aiming to answer 1) whether climate shapes cerrado fruiting phenology and its long-term changes; and 2) whether inter-annual variations on fruit timing are related to the El Niño Southern Oscillation (ENSO), the major driver of inter-annual climatic variability in the tropics; Our cerrado is located at Fazenda São José da Conquista, Itirapina, São Paulo State, Southeastern Brazil. The woody savanna is dominated by trees up to 8 m tall and comprises a typical cerrado (cerrado sensu strictu). We monitored the reproductive phenology of 2150 marked trees on a monthly basis, since 2004. We also analyzed the historical climate time series from a nearby climatic station (35-y time series). Standardized time series analyses and cross-correlation techniques were used to evaluate long-term trends and to test the relationship between climatic variables and phenology.
Results/Conclusions
Cerrado reproductive phenology was seasonal, although flowering had a higher degree of seasonality than fruiting. The cerrado flowering peak was in September, at the end of the dry season, whereas the peak of fruiting was in November, during the onset of the rainy season. The annual seasonal pattern was maintained throughout the 12 years of observations, but once we removed seasonality, we observed inter-annual changes in the percentage of individuals flowering and fruiting over time. The percentage of flowering or fruiting individuals showed positive anomalies during 2007-2009, reaching up to ten-fold of the mean observed values at the end of 2007 and beginning of 2008. The relatively large event of La Niña in 2006-2007 was correlated with the increased proportion of individuals and species flowering and fruiting. Flower and fruit production was also affected by local climate, mostly by minimum and mean temperatures, while precipitation was less important than expected for tropical seasonal vegetation. Our long-term study indicates, for the first time, the influence of climatic variability and El-Niño events on flower and fruit production in the cerrado vegetation, with consequences for the management and conservation of these highly diverse plant communities under the actual climate-change scenarios.