Reply to Leuzinger et al.: Drought-induced tree mortality temperature sensitivity requires pressing forward with best available science

Abstract

Forest and woodland vulnerability to tree mortality in response to future drought and warmer temperatures is emerging as a potentially critical impact of global change (1). We directly addressed this issue experimentally in our recent study (2), on which Leuzinger et al. comment (3). Notably, we showed drought-induced tree mortality was highly temperature-sensitive, raising concern about future die-off. Other experimental studies isolating the effect of warmer temperature on drought-induced tree mortality are lacking—a major knowledge gap given how directly such a relationship underpins the potential impacts of climate change. The shorter survival period under warmer temperatures quantified in our study correspondeds to a difference in leaf-level cumulative respiration—a response consistent with the temperature sensitivity of carbon dynamics driving differences in mortality. A simple projection of this sensitivity using a 103-year historical record of drought indicated that warmer temperatures (+4.3 °C) could increase die-off frequency 5-fold. Leuzinger et al. (3) note methodological concerns regarding the study, some of which are helpful in prioritizing future research to refine insights, but nonetheless do not negate the main findings. Furthermore, these concerns should not cloud the urgency with which the research community pursues additional research to develop an improved model of plant mortality.