Fig. 4

Principal component analysis for the trees of the five studied species, according to seven variables characterising or involved in drought response: (1) variables related to drought intensity experienced by the trees (Ψ_wp, Ψ_wm, SFD%, depth of root system), (2) variables characterising vulnerability to cavitation (Ψ₅₀, Slope) and (3) earliness of the growing season (budburst date). Ψ_wp and Ψ_wm were measured at the driest time of the 2006 summer, i.e. DOY 213 and 206, respectively. a Projection of the studied variables on the first factorial plane. b Projection of the trees on the same plane; each data point is one tree. Symbols correspond to species: Bp, B. pendula; Cb, C. betulus; Fs, F. sylvatica; Qr, Q. robur; Sc, S. capreae