Figure 1: Stand regions and moisture conditions across eastern United States deciduous forests. Aridity index values are mean Aridity-Witness Index (calculated as the fraction of mean annual precipitation to mean annual evapotranspiration) at 9 m spatial resolution from 1970–2000. Aridity index data were accessed from the CGIAR-CSI GeoPortal at https://cgiarcsi.community (Trabucco & Zomer, 2009).
Figure 2: Assessing the bias from open-vessel artifacts. Panel (a) and (d) are individual Q. alba and L. tulipifera embolism curves generated from samples collected in NC 85yo, Panel (b) (c) and (e) (f) are a comparison of threshold means across all samples from a one-way ANOVA between Q. alba and L. tulipifera respectively when partitioned by ‘r’ and ‘s’ shaped curves. Error bars are \(\pm 1\) standard error of the mean. Bars not sharing the same letters denote significant differences at α = 0.05
Figure 3: Embolism thresholds across forest stands. Panel (a) and (b) are mean P12 and P50 values ( \(\pm\)SE), respectively. Numbers above bars are sample size. Groups of bars not sharing the same uppercase letters denote significant differences among species determined by a two-way ANOVA with species and age as fixed factors and region as a blocking factor (Table 2).
Figure 4: Test of simple effects of significant interaction terms from two-way ANOVA by pairwise comparison of least square means. Panel (a) is least square mean P50 ( \(\pm\)SE) across forest ages for each species. Panel (b) is least square mean P50 ( \(\pm\)SE) across chronosequence regions for each forest age. Groups of bars not sharing the same uppercase letters denote significant differences of main effects at α = 0.05. Within groups, bars not sharing the same lowercase letters denote significant differences at α = 0.05.
Figure 5. Mean xylem lumen area ( \(\pm\)SE) of Q. alba and 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).
Figure 6: Mean vessel density ( \(\pm\)SE) of Q. alba and L. tulipifera and 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 and region as a blocking factor (Table 2). Panel (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). Solid lines are best fit across species and dashed line is at the species-level.
Figure 7: Midday leaf water potential (ΨL) observations across species and stands. Panel (a) is ΨLinterquartile range in each respective stand. Box‐plots show the median (middle line), interquartile range (box), and maximum/minimum value (whiskers), except where values exceed 1.5 times the interquartile range (points). Numbers above boxes are sample size. Panel (b) is mean interquartile range ( \(\pm\)SE) for each species. Bars not sharing the same uppercase letters denote significant differences across species by a two-way ANOVA with species and age as fixed factors.
Figure 8: Differences between isohydric behavior and embolism thresholds. Isohydric species are L. tulipifera and A. saccharum. Anisohydric species are Q. alba. Panel (a) and (c) are mean P12 and P50 values ( \(\pm\)SE), respectively. Bars not sharing the same uppercase letters denote significant differences (p ≤ 0.05) from two-tailed t-test.