title: The impacts of increasing drought on forest dynamics, structure, and biodiversity in the United States.
abstract: We synthesize insights from current understanding of drought impacts at stand-to-biogeographic scales, including management options, and we identify challenges to be addressed with new research. Large stand-level shifts underway in western forests already are showing the importance of interactions involving drought, insects, and fire. Diebacks, changes in composition and structure, and shifting range limits are widely observed. In the eastern US, the effects of increasing drought are becoming better understood at the level of individual trees, but this knowledge cannot yet be confidently translated to predictions of changing structure and diversity of forest stands. While eastern forests have not experienced the types of changes seen in western forests in recent decades, they too are vulnerable to drought and could experience significant changes with increased severity, frequency, or duration in drought. Throughout the continental United States, the combination of projected large climate-induced shifts in suitable habitat from modeling studies and limited potential for the rapid migration of tree populations suggests that changing tree and forest biogeography could substantially lag habitat shifts already underway. Forest management practices can partially ameliorate drought impacts through reductions in stand density, selection of drought-tolerant species and genotypes, artificial regeneration, and the development of multistructured stands. However, silvicultural treatments also could exacerbate drought impacts unless implemented with careful attention to site and stand characteristics. Gaps in our understanding should motivate new research on the effects of interactions involving climate and other species at the stand scale and how interactions and multiple responses are represented in models. This assessment indicates that, without a stronger empirical basis for drought impacts at the stand scale, more complex models may provide limited guidance.
authors.affiliation: Nicholas School of the Environment, Duke University, Durham, NC, 27708, USA.
authors.forename: James S
authors.initials: JS
authors.lastname: Clark
authors.affiliation: Forest Service, Northern Research Station, 359 Main Road, Delaware, OH, 43015, USA.
authors.forename: Louis
authors.initials: L
authors.lastname: Iverson
authors.affiliation: Forest Service, 1992 Folwell Avenue, Saint Paul, MN, 55108, USA.
authors.forename: Christopher W
authors.initials: CW
authors.lastname: Woodall
authors.affiliation: U.S. 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: Forest Service, Pacific Northwest Research Station, Corvallis, OR, 97331, USA.
authors.forename: David M
authors.initials: DM
authors.lastname: Bell
authors.affiliation: Forest Service, Southern Research Station, Monticello, AR, 71656, USA.
authors.forename: Don C
authors.initials: DC
authors.lastname: Bragg
authors.affiliation: Rubenstein School of Environment and Natural Resources, University of Vermont, 04E Aiken Center, 81 Carrigan Dr., Burlington, VT, 05405, USA.
authors.forename: Anthony W
authors.initials: AW
authors.lastname: D'Amato
authors.affiliation: Bren School of Environmental Science and Management, University of California, Santa Barbara, CA, 93106, USA.
authors.forename: Frank W
authors.initials: FW
authors.lastname: Davis
authors.affiliation: Department of Biology, Sarah Lawrence College, New York, NY, 10708, USA.
authors.forename: Michelle H
authors.initials: MH
authors.lastname: Hersh
authors.affiliation: School of Natural Resources and Environment, University of Michigan, 2546 Dana Building, Ann Arbor, MI, 48109, USA.
authors.forename: Ines
authors.initials: I
authors.lastname: Ibanez
authors.affiliation: U.S. Geological Survey, Southwest Climate Science Center and Department of Geosciences, University of Arizona, 1064 E. Lowell St., PO Box 210137, Tucson, AZ, 85721, USA.
authors.forename: Stephen T
authors.initials: ST
authors.lastname: Jackson
authors.affiliation: School of Environment and Natural Resources, Ohio State University, Columbus, OH, 43210, USA.
authors.forename: Stephen
authors.initials: S
authors.lastname: Matthews
authors.affiliation: Harvard Forest, Petersham, MA, 01366, USA.
authors.forename: Neil
authors.initials: N
authors.lastname: Pederson
authors.affiliation: Forest Service, Northern Research Station, Delaware, OH, 43015, USA.
authors.forename: Matthew
authors.initials: M
authors.lastname: Peters
authors.affiliation: Department of Environmental Science and Policy, UC Davis, Davis, CA, 93106, USA.
authors.forename: Mark W
authors.initials: MW
authors.lastname: Schwartz
authors.affiliation: School of Forestry, Northern Arizona University, Flagstaff, AZ, 86001, USA.
authors.forename: Kristen M
authors.initials: KM
authors.lastname: Waring
authors.affiliation: Swiss Federal Research Institute WSL, Birmensdorf, Switzerland.
authors.forename: Niklaus E
authors.initials: NE
authors.lastname: Zimmermann
mesh_terms: D044822:Biodiversity; D055864:Droughts; D017753:Ecosystem; D065928:Forests; D014197:Trees; D014481:United States
keywords: climate change; drought; forest dieback; forest management