Research Projects

Forests in a changing climate – Tropical forests are the reservoirs of Earth’s biodiversity, the engines that drive global carbon and water cycles, and the providers of ecosystem services to billions of people. Forests are increasingly threatened by climate change and other anthropogenic pressures such as land-use changes and habitat degradation. Climate variability is projected to increase in the future, causing more frequent and more intense extreme events such as droughts and heatwaves. Impacts of climate change on forests remain unclear: reports of drought-induced forest dieback have sparked concerns about species nearing their bioclimatic survival thresholds; yet, signs of post-drought recovery and resilience suggest that biodiverse ecosystems may have some capacity to acclimate and adapt to climate change. Plant hydraulics: a missing piece of the puzzle – Hydraulics is the mechanistic linchpin connecting plant physiology to the regional water cycle and ecosystem resilience during drought. Water stress causes loss of plant hydraulic conductivity, reducing transpiration and altering regional precipitation patterns. Persistent stress can induce cavitation in the xylem, leading to hydraulic failure and death. Hydraulic diversity insures ecosystems against drought, providing functional redundancy and enabling faster post-drought recovery. Even in agricultural systems, water-use traits govern crop yield under water stress. Yet, vegetation models that forecast ecosystem responses to climate change typically lack representation of plant hydraulics. Indeed, plant physiology remains a large source of uncertainty in vegetation-model predictions. State of the art and research challenges – Empirical research in plant hydraulics has grown exponentially in the past decade, providing valuable insights into the hydraulic control of plant transpiration, plant mortality, and plant life-history strategies. Next-generation vegetation models have begun to incorporate plant hydraulics. However, challenges remain in translating empirical insights into quantitative predictions, owing to (i) a mismatch between available data and data required by models, (ii) lack of requisite eco-physiological theory, and (iii) limited integration of theory and data into vegetation models, leading to their overparameterization and low predictive accuracy under novel climatic conditions. Objectives – This project aims to bring about a step change in our ability to predict forest responses to climate change. To that end, I will resolve the aforementioned challenges through empirical and theoretical innovations realised through the following objectives: 1. To characterise hydraulic diversity, trade-offs, and evolutionary adaptations among species in the Western Ghats through model-informed data collection. 2. To develop a unified theory for plant hydraulic adaptation based on eco-evolutionary principles. 3. To predict forest productivity, transpiration, and hydraulic adaptations along extant climatic gradients and under future climate scenarios, focusing on the Western Ghats. Hypotheses and rationale – (1) A trade-off between CO₂ uptake and risk of hydraulic failure gives rise to diverse plant hydraulic strategies, which are reflected in species-specific whole-plant vulnerability curves. Objective 1 will quantify this hydraulic diversity, hydraulic trade-offs, and hydraulic controls on transpiration and photosynthesis. (2) Eco-evolutionary theory predicts that species can coexist if they achieve similar fitness. I hypothesise that diverse hydraulic strategies yield similar annual carbon uptake rates - such “functional equifinality” can provide a basis for a unified theory of hydraulic adaptation. (3) Integrating such an eco-evolutionary theory into a vegetation model enables accurate forecasts of species-specific responses under future climate scenarios.