Isabelle Helfenstein, Joan T. Sturm, Bernhard Schmid, Alexander Damm, Meredith Christine Schuman , Felix Morsdorf

Mapping and predicting ecosystem responses to climate extremes is crucial in the face of global change. To what extent the behavior of non-experimental systems at large scales corresponds to the relationships discovered in biodiversity-ecosystem functioning (BEF) experiments remains unclear. We investigated the relationship between remotely-sensed trait-based diversity and drought responses in temperate forests in Switzerland during the hot, dry summer of 2018. Using Sentinel-2 data, we assessed the diversity of physiological canopy traits and quantified drought response in resistance, recovery, and resilience from 2017 to 2020. The BEF relationship between diversity and drought response revealed that forests with higher trait richness were more resistant and resilient, while trait evenness had a hump-shaped or negative relationship with resistance and resilience, respectively. These findings suggest that trait diversity supports drought response through complementarity and dominance effects. Our findings provide new insights into BEF relationships in non-experimental forest ecosystems.