Thermal Safety Margins and Peak Leaf Temperatures Predict Vulnerability of Diverse Plant Species to an Experimental Heatwave

Abstract

Extreme heat can push plants beyond their thermal safety margin (TSM) if maximum leaf temperature (Tleaf_max) exceeds leaf critical temperature (Tcrit). The TSM is potentially useful for assessing heat vulnerability across species but needs further validation, so we exposed 50 tree/shrub species in controlled glasshouses to a 6-day heatwave (peak air temperature = 41°C). Many species increased their mean Tcrit during the heatwave (42%), with ΔTcrit ranging from +1°C to 4°C, but other species did not acclimate or were impaired by heat stress (58%). Species Tleaf_max explained ~55% of the variation in species Tcrit and was a key correlate of the plasticity of Tcrit among species. Species with ..