Figure legends
Figure 1 Relationship of hydraulic and anatomical traits between branches and roots: (a) P 50, water potential at a 50% loss of hydraulic conductivity; (b)K S, specific xylem conductivity per unit of cross-sectional sapwood area; (c)t 2/b 2, vessel wall reinforcement; (d) D h, hydraulically weighted mean diameters (the x-axis and y-axis were natural log-transformed). Dashed line represents the 1:1 relationship. The coefficients of determination (r 2) of the simple linear regression models were marked. Each point denotes a species. Insert: comparison of traits between branches and roots. Boxes and whiskers represent the minimum, 25th percentile, median, 75th percentile, and maximum values in each bin, respectively. Solid points are outliers (data points located outside the whiskers of the boxplot). Numbers in the brackets are sample sizes. *** P < 0.001.
Figure 2 Relationships between P 50(water potential at a 50% loss of hydraulic conductivity) and anatomical traits (t 2/b 2, vessel wall reinforcement; D h, hydraulically weighted mean diameters) of branches and roots: (a)t 2/b 2 in branches, (b)t 2/b 2 in roots, (c)D h in branches, (d) D h in roots (the x-axis and y-axis were natural long-transformed). Each point denotes a species (branch traits: filled dark yellow circles and root traits: filled dark red triangles ). ***, P< 0.001.
Figure 3 Relationships between P 50 root - branch (hydraulic vulnerability segmentation between root and branch) and hydraulic traits (P 50, water potential at a 50% loss of hydraulic conductivity; K S, specific xylem conductivity per unit of cross-sectional sapwood area) of branches and roots: (a) P 50 of branches, (b)P 50 of roots, (c) K S of branches, (d) K S of roots (the x-axis and y-axis were natural long-transformed). Each point denotes a species (branch traits: filled dark yellow circles and root traits: filled dark red triangles ). Dashed line in (b) indicates nonsignificant correlations. Significance: ***, P < 0.001; **, 0.001 ≤P < 0.01.
Figure 4 Comparisons of hydraulic vulnerability segmentation (P 50 root - branch) and hydraulically weighted mean diameter (D h) across different biomes: (a)P 50 root - branch, (b) D hof branches, (c) D h of roots. Boxes and whiskers represent the minimum, 25th percentile, median, 75th percentile, and maximum values in each bin, respectively. Solid points are outliers defined as data points located outside the whiskers of the boxplot. The horizontal short dashed line indicates that P 50 root - branch is equal to zero (a). Mean values of AI for different biomes are shown (a). The numbers in the brackets are sample sizes. Different letters indicate statistically significant differences atP < 0.05 (one-way ANOVA). Inset: relationships betweenP 50 root - branch and aridity index (AI) (a), relationships between D h and AI of branches (b) and roots (c) (the x-axis and y-axis were natural log-transformed) across biomes. Each point denotes one species [filled green circles , tropical seasonal forest (TRS); filled aquamarine circles , temperate seasonal forest (TMS); filled dodger blue circles , woodland and shrubland (WDS); and filled purple circles , desert (DES)]. Dashed line in (c) indicates nonsignificant models. Significance: ***, P < 0.001; **, 0.001 ≤P < 0.01.