Mechanisms of plant survival and mortality during drought: why do some plants survive while others succumb to drought?
Severe droughts have been associated with regional-scale forest mortality worldwide. Climate change is expected to exacerbate regional mortality events; however, prediction remains difficult because the physiological mechanisms underlying drought survival and mortality are poorly understood. We developed a hydraulically based theory considering carbon balance and insect resistance that allowed development and examination of hypotheses regarding survival and mortality. Multiple mechanisms may cause mortality during drought. A common mechanism for plants with isohydric regulation of water status results from avoidance of drought-induced hydraulic failure via stomatal closure, resulting in carbon starvation and a cascade of downstream effects such as reduced resistance to biotic agents. Mortality by hydraulic failure per se may occur for isohydric seedlings or trees near their maximum height. Although anisohydric plants are relatively drought-tolerant, they are predisposed to hydraulic failure because they operate with narrower hydraulic safety margins during drought. Elevated temperatures should exacerbate carbon starvation and hydraulic failure. Biotic agents may amplify and be amplified by drought-induced plant stress. Wet multidecadal climate oscillations may increase plant susceptibility to drought-induced mortality by stimulating shifts in hydraulic architecture, effectively predisposing plants to water stress. Climate warming and increased frequency of extreme events will probably cause increased regional mortality episodes. Isohydric and anisohydric water potential regulation may partition species between survival and mortality, and, as such, incorporating this hydraulic framework may be effective for modeling plant survival and mortality under future climate conditions.
McDowell
Nate
N
Earth and Environmental Sciences Division, Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
Pockman
William T
WT
Department of Biology, MSC03 2020, 1 University of New Mexico, Albuquerque, NM 87131-0001, USA.
Allen
Craig D
CD
US Geologcial Survey, Jemez Mountains Field Station, 15 Entrance Road, Los Alamos, NM 87544, USA.
Breshears
David D
DD
School of Natural Resources, Institute for the Study of Planet Earth, and Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721-0043, USA.
Cobb
Neil
N
Merriam-Powell Center for Environmental Research, Peterson Hall, Bldg 22, Rm 330, Box 6077, Northern Arizona University Flagstaff, AZ 86011, USA.
Kolb
Thomas
T
School of Forestry, Northern Arizona University, Flagstaff, AZ 86001-5018, USA.
Plaut
Jennifer
J
Department of Biology, MSC03 2020, 1 University of New Mexico, Albuquerque, NM 87131-0001, USA.
Sperry
John
J
Department of Biology, University of Utah, 257S 1400E, Salt Lake City, UT 84112, USA.
West
Adam
A
Department of Integrative Biology, University of California, Berkeley, CA 94720.|Botany Department, University of Cape Town, Private Bag, Rondebosch, 7700, South Africa.
Williams
David G
DG
Department of Renewable Resources, University of Wyoming, Laramie, WY 82071 USA.
Yepez
Enrico A
EA
Department of Biology, University of New Mexico, Albuquerque, NM 87131, USA.
D000222:Adaptation, Physiological; D002980:Climate; D004190:Disasters; D008954:Models, Biological; D018521:Plant Physiological Phenomena