Seminar: Monitoring Drought-Induced Tree Mortality as an Ecological Process

Drought is expected to become one of the most important global drivers of forest dieback under climate change. Yet predicting when and where tree mortality will occur remains difficult because drought responses differ among forest types, species, and individuals (e.g., due to life history or genetic traits). Mortality often results from a chain of ecological events—such as carbon starvation, hydraulic failure, or reduced resistance to insects and wildfires—and depends on how drought severity changes in intensity, frequency, and duration. 

Because the sequence of these events can vary across species, their survival strategies, and drought histories, i.e. their frequency, intensity, and duration, drought-induced mortality should be viewed as a complex ecological process rather than as an isolated event without preceding changes. We propose to monitor this process as a progressive loss of resilience, or increasing stress perceived as droughts intensify or recur. This perspective allows tracking of indicators along the entire pathway from a healthy tree or forest to mortality or degradation, from early, reversible signals to later, high-certainty indicators (e.g., structural damage).

By linking generic resilience theory with process-based stress metrics (e.g., hydraulic, gas-exchange, and photosynthetic changes), we aim to improve understanding of mortality mechanisms and support early warning systems from individual trees to entire biomes.