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.

This research aims to develop novel supramolecular hydrogels and study their application as singlet oxygen (1O2) carriers. In medicine, 1O2 generated in-vivo through photochemistry has been used to treat a variety of ailments including bacterial infections, acne, and several types of cancer. Though promising, this approach suffers from drawbacks such as diminished effectiveness in hypoxic conditions, both native and induced and lack of control over the total concentration and dosage of active 1O2. Recently, endoperoxides (EPO) have been identified as a potential solution for those, as they are self-contained sources of 1O2 produced ex-situ. However, they still do not allow for precise spatiotemporal control of 1O2 release, which is desirable to maximize for effectiveness of the treatment. Grafting EPOs on solid supports has been explored as a solution, but the state-of-the-art materials rely on complicated supports with low EPO loadings and thermal release mechanisms. Herein, we propose a new strategy for spatiotemporal control of 1O2 through the unprecedented use of hydrogels as EPO carriers. Hydrogels offer an easy to control and stable, but not persistent matrix in which the main component is water. The OTHO (oxotriphenylhexanoate) hydrogels enjoy unparalleled modularity, due to their highly robust and selective multicomponent one-pot synthesis. Thus, we will synthesize a range of OTHOs containing EPO units and perform detailed studies by rheology, solid-state NMR, small-angle x-ray and neutron scattering and electron microscopy to understand the properties and behavior of the resulting hydrogels. The biocompatibility and cytotoxic profile of the materials will be investigated against yeast cells expressing human disease markers. This will pave the way for a new breed of supramolecular pharmacology materials for 1O2 therapy against cancer.