Chapter 7 Tree Physiology and Intraspecific Responses to Extreme Events: Insights from the Most Extreme Heat Year in U.S. History

Abstract

Extreme weather events, including heat waves and droughts, are increasing as a result of climate change, and these events are occurring within the context of gradual increases in global mean temperatures over decadal to century timescales. Trees are especially vulnerable to extreme events and their physiological responses to these conditions may dictate their ability to survive and persist under future climate change. Recent studies indicate that extreme weather events can directly or indirectly weaken trees to the point of mortality, and when compounded over space and time, this has the potential to alter ecosystem functioning and the global carbon cycle more broadly. Furthermore, extreme events can potentially impact the evolutionary trajectory of trees, with rapid selection favoring a subset of survivors with altered physiologies, assuming genetic variation is sufficient to allow for survival in the first place. Unfortunately, the impacts of extreme years on the physiological functioning of trees at the intraspecific level are not well understood, hindering our ability to predict long-term consequences of extreme events on the survival and evolutionary trajectories of tree species.