Tree Die-Off in Response to Global Change-Type Drought: Mortality Insights from a Decade of Plant Water Potential Measurements

Authors

David D. Breshears, University of Arizona, Tucson, AZ
Orrin B. Meyers, University of New Mexico Health Sciences, Albuquerque, NM
Clifton W. Meyer, Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM
Fairley J. Barnes, Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM
Chris B. Zou, University of Arizona, Tucson, AZ
Craig D. Allen, US Geological Survey, Jemez Mountains Field StationFollow
Nathan G. McDowell, Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM
William Pockman, University of New Mexico, Albuquerque, NM

Date of this Version

2009

Comments

Published in Front Ecol Environ 2009; 7(4): 185–189, doi:10.1890/080016.

Abstract

Global climate change is projected to produce warmer, longer, and more frequent droughts, referred to here as “global change-type droughts”, which have the potential to trigger widespread tree die-off. However, drought-induced tree mortality cannot be predicted with confidence, because long-term field observations of plant water stress prior to, and culminating in, mortality are rare, precluding the development and testing of mechanisms. Here, we document plant water stress in two widely distributed, co-occurring species, piñon pine (Pinus edulis) and juniper (Juniperus monosperma), over more than a decade, leading up to regional-scale die-off of piñon pine trees in response to global change-related drought. Piñon leaf water potentials remained substantially below their zero carbon assimilation point for at least 10 months prior to dying, in contrast to those of juniper, which rarely dropped below their zero-assimilation point. These data suggest that piñon mortality was driven by protracted water stress, leading to carbon starvation and associated increases in susceptibility to other disturbances (eg bark beetles), a finding that should help to improve predictions of mortality during drought.