期刊
SCIENCE
卷 323, 期 5913, 页码 521-524出版社
AMER ASSOC ADVANCEMENT SCIENCE
DOI: 10.1126/science.1165000
关键词
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资金
- NSF's Long-term Studies Program [DEB-0218088]
- Wind River Canopy Crane Program [PNW 08-DG- 11261952488]
- USDA Forest Service's Pacific Northwest
- Pacific Southwest
- Rocky Mountain research stations
- McIntire-Stennis Cooperative Forestry Program
- NSF [DEB-0743498, BCS-0825823]
- Natural Science and Engineering Research Council of Canada
- U.S. National Park Service
- U.S. Geological Survey
- Division Of Environmental Biology
- Direct For Biological Sciences [0823380] Funding Source: National Science Foundation
Persistent changes in tree mortality rates can alter forest structure, composition, and ecosystem services such as carbon sequestration. Our analyses of longitudinal data from unmanaged old forests in the western United States showed that background ( noncatastrophic) mortality rates have increased rapidly in recent decades, with doubling periods ranging from 17 to 29 years among regions. Increases were also pervasive across elevations, tree sizes, dominant genera, and past fire histories. Forest density and basal area declined slightly, which suggests that increasing mortality was not caused by endogenous increases in competition. Because mortality increased in small trees, the overall increase in mortality rates cannot be attributed solely to aging of large trees. Regional warming and consequent increases in water deficits are likely contributors to the increases in tree mortality rates.
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