Multi-biome assessment of tree water use resilience to drought

Drought frequency and severity are increasing in many regions, impacting forest functioning and dynamics, with effects that can result in widespread tree death and ecosystem shifts. These events have been linked to soil and atmospheric hydrological changes, but the causes of different responses in tree water-use are poorly understood at the global scale. We used data from the SAPFLUXNET global database to assess water-use resilience to drought of > 900 trees of 96 different species in 89 plots distributed across the globe. We detected decreases in water-use resilience when soil water availability was lower before, during or after the drought. Atmospheric drought enhanced resilience during the pre-drought period, but diminished it post-drought. Resilience was also favoured by longer recovery periods since the last, previous drought, and in larger diameter trees. Hydraulic and water relations traits also played a role in determining differences in tree water-use resilience across species. Species that were more vulnerable to stem xylem embolism (less negative P50) or had a more negative turgor loss point exhibited higher water-use resilience (and resistance). Our findings help to better understand the drivers of water use resilience and therefore contribute to our understanding of how trees respond to severe droughts at multiple spatio-temporal scales.