title: Regional vegetation die-off in response to global-change-type drought.
abstract: Future drought is projected to occur under warmer temperature conditions as climate change progresses, referred to here as global-change-type drought, yet quantitative assessments of the triggers and potential extent of drought-induced vegetation die-off remain pivotal uncertainties in assessing climate-change impacts. Of particular concern is regional-scale mortality of overstory trees, which rapidly alters ecosystem type, associated ecosystem properties, and land surface conditions for decades. Here, we quantify regional-scale vegetation die-off across southwestern North American woodlands in 2002-2003 in response to drought and associated bark beetle infestations. At an intensively studied site within the region, we quantified that after 15 months of depleted soil water content, >90% of the dominant, overstory tree species (Pinus edulis, a piñon) died. The die-off was reflected in changes in a remotely sensed index of vegetation greenness (Normalized Difference Vegetation Index), not only at the intensively studied site but also across the region, extending over 12,000 km2 or more; aerial and field surveys confirmed the general extent of the die-off. Notably, the recent drought was warmer than the previous subcontinental drought of the 1950s. The limited, available observations suggest that die-off from the recent drought was more extensive than that from the previous drought, extending into wetter sites within the tree species' distribution. Our results quantify a trigger leading to rapid, drought-induced die-off of overstory woody plants at subcontinental scale and highlight the potential for such die-off to be more severe and extensive for future global-change-type drought under warmer conditions.
authors.affiliation: 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. daveb@email.arizona.edu
authors.forename: David D
authors.initials: DD
authors.lastname: Breshears
authors.forename: Neil S
authors.initials: NS
authors.lastname: Cobb
authors.forename: Paul M
authors.initials: PM
authors.lastname: Rich
authors.forename: Kevin P
authors.initials: KP
authors.lastname: Price
authors.forename: Craig D
authors.initials: CD
authors.lastname: Allen
authors.forename: Randy G
authors.initials: RG
authors.lastname: Balice
authors.forename: William H
authors.initials: WH
authors.lastname: Romme
authors.forename: Jude H
authors.initials: JH
authors.lastname: Kastens
authors.forename: M Lisa
authors.initials: ML
authors.lastname: Floyd
authors.forename: Jayne
authors.initials: J
authors.lastname: Belnap
authors.forename: Jesse J
authors.initials: JJ
authors.lastname: Anderson
authors.forename: Orrin B
authors.initials: OB
authors.lastname: Myers
authors.forename: Clifton W
authors.initials: CW
authors.lastname: Meyer
mesh_terms: D002980:Climate; D004190:Disasters; D017753:Ecosystem; D006358:Hot Temperature; D015206:Southwestern United States; D014197:Trees / Q000502:physiology*