Fig. 1: Time series of stomatal conductance (gs) and pre-dawn leaf water potentials (Ψleaf) collected using a canopy crane at the Swiss Canopy Crane II (SCCII) site.
a, Mean species-specific midday gs measured on leaves from the top of the canopy, shown with large, coloured circles. Open circles indicate measurement dates where Ψleaf was below −1.2 MPa. Grey dots represent raw measurements. b, Pre-dawn (04:00–06:00 CET) Ψleaf, with coloured dots indicating the species mean. In 2022 an exceptional drought caused all Ψleaf to drop below −1.2 MPa (shown with open circles). c, Theoretical example of how the point of stomatal closure (Pst) was defined. Pst was assumed when the negative exponential behaviour of gs changed to a linear decrease (Supplementary Methods). Midday Ψleaf values are presented in Supplementary Fig. 3. J through D, months of January through December.
