The response of tropical forest –savanna transitions has received much attention in the scientific literature over the last years. However, most studies use global models or remote sensing approaches that represent the transition from forest to savanna as a competition between a few functional groups (often just two groups: tropical grasses and tropical trees). There is plenty evidence that the transition between tropical forest and non-forest biomes is not gradual, but a threshold phenomenon between two stable states that can occur at the same level of rainfall. The switch between these two stable states has been suggested to be primarily mediated by fire, although light, nutrients and other factors can also mediate this transition.
This proposal aims to gather a detailed ecological and ecophysiological understanding of the dynamic process of tropical forest-savanna transition, at a number of sites of South America and Africa. The study is framed in the context of the forest-savanna fire thresholds from a functional trait perspective, with the aim of testing and further developing the role of fire and its interaction with drought and resources availability. This will be achieved through detailed plot surveys to understand and quantify the tree mortality and recruitment processes, and through targeted manipulative experiments to understand and quantify responses to fire, drought, light and nutrient availability. This will enable the applicant to explicitly evaluate forest and savanna species’ ecological response to fire and to multiple interacting abiotic factors and provide a useful model to describe the process of possible tropical forest dieback and/or woody encroachment under some scenarios of climate change.