title: Tree mortality from drought, insects, and their interactions in a changing climate.
abstract: Climate change is expected to drive increased tree mortality through drought, heat stress, and insect attacks, with manifold impacts on forest ecosystems. Yet, climate-induced tree mortality and biotic disturbance agents are largely absent from process-based ecosystem models. Using data sets from the western USA and associated studies, we present a framework for determining the relative contribution of drought stress, insect attack, and their interactions, which is critical for modeling mortality in future climates. We outline a simple approach that identifies the mechanisms associated with two guilds of insects - bark beetles and defoliators - which are responsible for substantial tree mortality. We then discuss cross-biome patterns of insect-driven tree mortality and draw upon available evidence contrasting the prevalence of insect outbreaks in temperate and tropical regions. We conclude with an overview of tools and promising avenues to address major challenges. Ultimately, a multitrophic approach that captures tree physiology, insect populations, and tree-insect interactions will better inform projections of forest ecosystem responses to climate change.
authors.affiliation: Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, 08540, USA.
authors.forename: William R L
authors.initials: WR
authors.lastname: Anderegg
authors.affiliation: Department of Geography, University of Idaho, Moscow, ID, 83844, USA.
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Hicke
authors.affiliation: National Center for Atmospheric Research, Boulder, CO, 80305, USA.
authors.forename: Rosie A
authors.initials: RA
authors.lastname: Fisher
authors.affiliation: US Geological Survey, Fort Collins Science Center, Jemez Mountains Field Station, Los Alamos, NM, 87544, USA.
authors.forename: Craig D
authors.initials: CD
authors.lastname: Allen
authors.affiliation: National Center for Ecological Analysis and Synthesis, Santa Barbara, CA, 93117, USA.
authors.forename: Juliann
authors.initials: J
authors.lastname: Aukema
authors.affiliation: USDA Forest Service, Rocky Mountain Research Station, Logan, UT, 84321, USA.
authors.forename: Barbara
authors.initials: B
authors.lastname: Bentz
authors.affiliation: Division of Biological Sciences, The University of Montana, Missoula, MT, 59812, USA.
authors.forename: Sharon
authors.initials: S
authors.lastname: Hood
authors.affiliation: Department of Biology, University of Florida, Gainesville, FL, 32611, USA.
authors.forename: Jeremy W
authors.initials: JW
authors.lastname: Lichstein
authors.affiliation: School of Geography and Development, University of Arizona, Tucson, AZ, 85712, USA.
authors.forename: Alison K
authors.initials: AK
authors.lastname: Macalady
authors.affiliation: Earth and Environmental Sciences Division, Los Alamos National Lab, Los Alamos, NM, 87545, USA.
authors.forename: Nate
authors.initials: N
authors.lastname: McDowell
authors.affiliation: Northern Research Station, US Forest Service, Newtown Square, PA, 19073, USA.
authors.forename: Yude
authors.initials: Y
authors.lastname: Pan
authors.affiliation: Department of Entomology, University of Wisconsin, Madison, WI, 53706, USA.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Raffa
authors.affiliation: Division of Biological Sciences, The University of Montana, Missoula, MT, 59812, USA.
authors.forename: Anna
authors.initials: A
authors.lastname: Sala
authors.affiliation: Rocky Mountain Research Station, US Forest Service, Ogden, UT, 84401, USA.
authors.forename: John D
authors.initials: JD
authors.lastname: Shaw
authors.affiliation: US Geological Survey, Western Ecological Research Center, 47050 Generals Highway No. 4, Three Rivers, CA, 93271, USA.
authors.forename: Nathan L
authors.initials: NL
authors.lastname: Stephenson
authors.affiliation: Bren School of Environmental Science and Management, University of California - Santa Barbara, Santa Barbara, CA, 93106, USA.
authors.forename: Christina
authors.initials: C
authors.lastname: Tague
authors.affiliation: Department of Biological Sciences, Macquarie University, Sydney, NSW, 2109, Australia.
authors.forename: Melanie
authors.initials: M
authors.lastname: Zeppel
mesh_terms: D000818:Animals; D057231:Climate Change; D055864:Droughts; D060434:Herbivory; D007313:Insecta / Q000502:physiology*; D014197:Trees / Q000502:physiology*
keywords: biosphere-atmosphere feedbacks; carbon cycle; disturbance; dynamic global vegetation model; trophic interactions