Coordinated hydraulic traits influence the two phases of time to hydraulic failure in five temperate tree species differing in stomatal stringency

• Published in: Tree physiology 2024-05, Vol.44 (5)
• Main Authors: Waite, Pierre-André, Kumar, Manish, Link, Roman M, Schuldt, Bernhard
• Format: Article
• Language: English
• Subjects: Droughts; Plant Stomata - physiology; Plant Transpiration - physiology; Species Specificity; Trees - physiology; Water - metabolism; Water - physiology; Xylem - physiology
• ISSN: 1758-4469; 1758-4469
• DOI: 10.1093/treephys/tpae038

Worldwide, forests are increasingly exposed to extreme droughts causing tree mortality. Because of the complex nature of the mechanisms involved, various traits have been linked to tree drought responses with contrasting results. This may be due to species-specific strategies in regulating water potential, a process that unfolds in two distinct phases: a first phase until stomatal closure, and a second phase until reaching lethal xylem hydraulic thresholds. We conducted dry-down experiments with five broadleaved temperate tree species differing in their degree of isohydry to estimate the time to stomatal closure (tsc) and subsequent time to critical hydraulic failure (tcrit). We measured various traits linked to tree drought responses, such as the water potentials at turgor loss point (Ptlp), stomatal closure (Pgs90), and 12%, 50% and 88% loss of xylem hydraulic conductance (P12, P50, P88), hydraulic capacitance (C), minimum leaf conductance (gmin), hydroscape area (HSA) and hydraulic safety margins (HSM). We found that Pgs90 followed previously recorded patterns of isohydry and was associated with HSA. Species ranked from more to less isohydric in the sequence Acer pseudoplatanus