Figure 4.

Calibration of the three different xylem vulnerability models [Weibull model (WB, A), the Sigmoid Exponential (SE, B), and the original SOX formulation (SOXf, C)] for the P. sylvestris saplings. Solid transparent lines are the five measured curves of the observed percent loss in xylem conductivity (PLC, in %) in relation to xylem water potential decrease (Ψ_xylem, in -MPa). Solid blue line ± shadowed blue area is the median ± 95 CI obtained from 1 k model runs sampling the combined posterior parameter estimate, resulting from curve-individual calibrations for each model, as described in section Xylem Vulnerability. The vertical solid line shows the Ψ₅₀ value; this is when xylem has lost 50% of its conductivity (±95% CI, vertical dashed lines). For each model, formulation and median ± 95% CI values for each parameter are provided. Note that in the WB model Ψ_ref parameter meaning is not equivalent to the Ψ₅₀ parameter from the other two models. Goodness of fit is given as the median pseudo-R² and the median root mean square error (RMSE) of all model runs.