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Wang W, English NB, Grossiord C, Gessler A, Das AJ, Stephenson NL, Baisan CH, Allen CD, McDowell NG. Mortality predispositions of conifers across western USA. New Phytol 2021; 229:831-844. [PMID: 32918833 DOI: 10.1111/nph.16864] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/19/2020] [Accepted: 08/03/2020] [Indexed: 06/11/2023]
Abstract
Conifer mortality rates are increasing in western North America, but the physiological mechanisms underlying this trend are not well understood. We examined tree-ring-based radial growth along with stable carbon (C) and oxygen (O) isotope composition (δ13 C and δ18 O, respectively) of dying and surviving conifers at eight old-growth forest sites across a strong moisture gradient in the western USA to retrospectively investigate mortality predispositions. Compared with surviving trees, lower growth of dying trees was detected at least one decade before mortality at seven of the eight sites. Intrinsic water-use efficiency increased over time in both dying and surviving trees, with a weaker increase in dying trees at five of the eight sites. C starvation was a strong correlate of conifer mortality based on a conceptual model incorporating growth, δ13 C, and δ18 O. However, this approach does not capture processes that occur in the final months of survival. Ultimately, C starvation may lead to increased mortality vulnerability, but hydraulic failure or biotic attack may dominate the process during the end stages of mortality in these conifers.
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Affiliation(s)
- Wenzhi Wang
- Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland, WA, 99352, USA
- The Key Laboratory of Mountain Environment Evolution and Regulation, Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu,, 610041, China
| | - Nathan B English
- School of Health, Medical and Applied Science, Central Queensland University, Townsville, QLD, 4810, Australia
| | - Charlotte Grossiord
- Functional Plant Ecology, Community Ecology Unit, Swiss Federal Institute for Forest, Snow and Landscape WSL, Lausanne,, CH-1015, Switzerland
- Plant Ecology Research Laboratory PERL, School of Architecture, Civil and Environmental Engineering, EPFL, Lausanne,, CH-1015, Switzerland
| | - Arthur Gessler
- Functional Plant Ecology, Community Ecology Unit, Swiss Federal Institute for Forest, Snow and Landscape WSL, Lausanne,, CH-1015, Switzerland
- Institute of Terrestrial Ecosystems, ETH Zurich, Universitaetsstrasse 16, Zurich, 8092, Switzerland
| | - Adrian J Das
- Western Ecological Research Center, US Geological Survey, Three Rivers, CA, 93271, USA
| | - Nathan L Stephenson
- Western Ecological Research Center, US Geological Survey, Three Rivers, CA, 93271, USA
| | | | - Craig D Allen
- Fort Collins Science Center, New Mexico Landscapes Field Station, US Geological Survey, Los Alamos, NM,, 87544, USA
| | - Nate G McDowell
- Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland, WA, 99352, USA
- School of Biological Sciences, Washington State University, Pullman, WA, 99164-4236, USA
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