Tropical tree mortality in a changing climate
Climate change increases tree mortality worldwide, and in tropical forests in particular. While it is established that tropical tree mortality increases under hot and dry conditions, key questions regarding why and how remain unresolved. Which traits predispose trees to mortality? How does drought and heat interact to affect tropical tree growth and survival under field conditions? The overall goal of my project is to determine the sensitivity of tropical tree species to heat and drought, and based on this knowledge develop a trait-based tree mortality model that can be used to provide recommendations on which trees are suitable to different climatic regions in Rwanda, central Africa. Such recommendations are crucial for reforestation programs and climate change adaptation in Rwanda, a low-income country which has been heavily deforested in the past. To achieve this goal, I will identify which tree traits (structural, hydraulic, physiological, biochemical) that control the vitality and survival of tropical trees in multi-species plantations established at three sites in Rwanda. The sites exhibit large natural variation in precipitation and temperature, and experimental manipulations of water supply (irrigation, rainfall exclusion) are imposed at each site. Traits will be determined using a broad range of gas exchange, hydraulic and biochemical methods in the field as well as in the lab. A multi-trait model of drought- and heat-induced tree mortality will be derived based on data from the experimental sites, and evaluated using independent data from additional sites with larger trees. Based on this model, I will provide tree plantation recommendations to relevant stakeholders in Rwanda and the region. By bringing together perspectives from experimental ecology and vegetation modelling to address critical knowledge gaps this projects will make original contributions to improve the understanding and predictability of tropical tree mortality in a changing climate.