Warmer temperature has been predicted for Earth’s future for many years. In fact, global temperature has been increasing somewhere between 0.1° C and 0.3° C per decade and rose to approximately 1° C above pre-industrial levels in 2017. Imbedded in this mean temperature increase, are extreme temperature events commonly referred to as heatwaves. Unfortunately, there is almost no information regarding interactions between increased “mean” global temperature and “extreme” temperature events (heatwaves) and their individual and collective effects on drought and large-scale vegetation mortality. There remains a great need for controlled experiments to tease apart the effects of mean temperature and extreme temperature events especially in areas where rainfall has been predicted to become more erratic resulting in an increase in drought duration, frequency, and intensity. To improve understanding of anthropogenic temperature change and temperature effects on Earth’s vegetation, especially forests, we performed an experiment on pinyon pine seedlings exposed to drought, above ambient air temperature, and heatwaves. Stomatal conductance, soil moisture loss, and time to mortality were measured to test the effects of mean temperature, extreme temperature events, and drought on stomatal closure and eventual mortality.
Results/Conclusions
Results are consistent with prior studies showing a decrease in time to mortality with increased temperature and decreased soil moisture. Notably, we show that in addition to a decrease in time to mortality with increased temperature, there is also a decrease in time to start of morality and a shorter mortality period with increasing temperature. These results highlight the dire consequences of warmer drought combined with heatwaves, as trees are likely to die more quickly in a shorter window of mortality under projected future conditions. These results also relate to other recent research highlighting risks from heat waves. Time to mortality and mortality duration, mean temperature, extreme temperature events, soil moisture, and their relationships are important parameters for global models to continue to accurately predict the effects of mean anthropogenic warming and extreme temperature events on the longevity of pinyon pine woodlands and other important ecosystems around the globe.