New paper in PNAS about hydraulic collapse as the cause of drought-induced mortality in conifers
Matthias Arend, Rachel Patthey, Günter Hoch, Ansgar Kahmen, and their co-authors conducted an important study on the mechanisms of tree mortality during the unprecedented Central European summer drought in 2018. The study tracked dynamic changes in water relations and the limits of hydraulic function in dying adult Norway spruce trees at the Swiss Canopy Crane II research site in Hölstein during the progression of the entire drought event. This work shows that clear, sudden, and non-linear declines in xylem pressure and hydraulic conductance resulted in rapid collapse of tree hydraulic systems and tree death. The threshold response suggests a higher mortality risk than previously assumed for this major European tree species.