Figure 5. Mean xylem lumen area (\(\pm\)SE) of Q. albaand L. tulipifera samples across chronosequences (Panel (a)) and age (Panel (c)). Groups of bars not sharing the same uppercase letters denote significant differences (p ≤ 0.05) between species, while bars within groups not sharing letters denote differences within species among ages or chronosequences from a two-way ANOVA with species and age as fixed factors. Panels (b) and (d) show the relationship between mean lumen area and mean specific embolism threshold of individual trees assessed by linear regression. Lines are best fit from linear regression when slope is significant (p ≤ 0.05).