IMPACTS OF GLOBAL CLIMATE CHANGE ON THE PHENOLOGY OF AFRICAN TROPICAL ECOSYSTEMS

The climate has been changing at an unprecedented rate, affecting natural systems around the globe. Its impact has been mostly reflected through changes in species’ phenology, which has received extensive attention in the current global-change research, mainly in temperate regions. However, little is known about phenology in African tropical forests. Africa is known to be vulnerable to climate change and filling the gaps is an urgent matter. In this study we assess plant phenology at the individual, site and continental level. We first compare flowering and fruiting events of species shared between multiple sites, accounting for three quantitative indicators, such as frequency, fidelity for conserving a certain frequency and seasonal phase. We complement this analysis by assessing interannual trends of flowering and fruiting frequency and fidelity to their dominant frequency at 11 sites. We complete the bigger picture by analysing flowering and fruiting frequency of African tropical trees at the site and community level. Next, we correlate three climatic indices (ENSO, IOD and NAO) with flowering and fruiting events at the canopy level, at 16 sites. Our results suggest that 30 % of the studied species show plasticity or adaptability to different environments and will most likely be resilient to moderate future climate change. At both site and continental level, we found that annual flowering cycles are dominant, indicating strong seasonality in the case of more than 50% of African tropical species under investigation. We also found that individuals flower and fruit less frequently over time, most probably due to senescence or a possible climate change impact. Moreover, results indicate that flowering and fruiting events of around 30% of species are correlated with one or more climatic phenomenon. However, their response to drier or wetter conditions is variable, highlighting the wide varieties of mechanisms African tropical trees adopt in relation to stress conditions. Altogether, this study fills important gaps and highlights the uniqueness of African tropical forests not reported before.