Lower Stem Freezing Point Tied to Greater Frost Embolism Vulnerability: A Comparison Between Ring- and Diffuse-Porous...

Area of Science:

• Plant Physiology
• Forest Ecology
• Climate Change Biology

Background:

• Temperate ring-porous trees have large earlywood vessels, making them vulnerable to freezing-induced embolism.
• Spring frosts pose a significant risk to the hydraulic function of these trees, despite their ability to form new vessels.

Purpose of the Study:

• To test the hypothesis that ring-porous temperate trees use enhanced freezing avoidance to protect vulnerable earlywood vessels.
• To compare the strategies of ring-porous and diffuse-porous species in coping with spring frost stress.

Main Methods:

• Quantified embolism in overwintering stems across 20 temperate tree species (11 ring-porous, 9 diffuse-porous).
• Measured ice nucleation temperature (INT_xylem), xylem water content (WC_xylem), and non-structural carbohydrate (NSC) concentrations.

Main Results:

• Ring-porous species experienced severe winter embolism and showed stronger spring freezing avoidance.
• Ring-porous species lowered INT_xylem through reduced WC_xylem and higher NSC concentrations, unlike diffuse-porous species.

Conclusions:

• Ring-porous trees employ freezing avoidance strategies (lower INT_xylem, reduced WC_xylem, higher NSC) to protect earlywood vessels from frost damage.
• Distinct strategies exist between ring-porous and diffuse-porous trees for managing spring frost stress, with implications for forest responses to climate change.