Water-use strategies determining growth and survival of tropical trees under heat and drought

Tropical trees play a key role in climate change adaptation and mitigation.

The ability of both intact tropical forests and newly planted trees to take up and store carbon in the long term depends on tree water economy in a changing climate.

In this project, we use a unique elevation gradient experiment in Rwanda to identify water-use strategies controlling growth and survival of a broad range of tropical tree species under heat and drought.

The experiment includes 5400 trees of 20 species grown at three sites with large variation in climate (18-24 °C mean daytime temperature; 1050-2100 mm precipitation). Water manipulation treatments (irrigation, rainfall exclusion) are applied at all sites.

We will determine plant traits affecting tree water economy (uptake, storage, transport, loss) and to what extent these traits can acclimate to heat and drought.

Together with multi-year observations of tree growth and survival, these data will be used to identify key traits and strategies controlling species’ climate sensitivity.

A mechanistic tree-water model will be used to integrate and evaluate influences of different traits, and a vegetation model will be applied to explore large-scale and long-term implications of key findings.

Knowledge gained will also be used to give recommendations on species selection for tree plantation in Rwanda and beyond.

The project is a collaboration between partners in Rwanda and Sweden and involves key stakeholders in the forest/forestry sector.