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Apparent climatically induced increase of tree mortality rates in a temperate forest
Phillip J van Mantgem1, Nathan L Stephenson
1U.S. Geological Survey, Western Ecological Research Center, Sequoia and Kings Canyon Field Station, 47050 Generals Highway #4, Three Rivers, CA 93271, USA. pvanmantgem@usgs.gov
Ecology Letters
|September 12, 2007
Summary
Temperate forest tree mortality increased significantly over 22 years due to drought stress, while recruitment remained stable. These findings suggest forests may face die-back with rising temperatures and insufficient precipitation.
Area of Science:
- Ecology
- Forest Science
- Climate Change Biology
Background:
- Long-term demographic data are crucial for understanding forest dynamics.
- Temperate forests, particularly old-growth ecosystems, are sensitive to environmental changes.
- Previous studies have indicated potential climate change impacts on forest health.
Purpose of the Study:
- To analyze long-term, annual-resolution demographic trends in a Sierra Nevada temperate forest.
- To investigate changes in tree mortality and recruitment rates over a 22-year period.
- To identify factors influencing demographic shifts in response to environmental variables.
Main Methods:
- Monitoring the fates of 21,338 trees across old-growth forest plots in the Sierra Nevada.
- Analyzing demographic data with annual resolution from 1983 to 2004.
- Correlating demographic trends with climate data, including drought indices and temperature.
Main Results:
- A significant increase in tree mortality rate was observed over the 22-year study period.
- Recruitment rate remained stable, showing no significant change.
- Increased mortality was linked to stress and biotic factors, coinciding with a temperature-driven drought index increase.
- Mortality rates rose in dominant genera (Abies, Pinus) and across different elevational zones.
Conclusions:
- Sierra Nevada temperate forests exhibit increased sensitivity to temperature-driven drought stress.
- Water-limited forests may be vulnerable to die-back under future climate scenarios with rising temperatures and reduced precipitation.
- These findings highlight the need for adaptive forest management strategies in response to climate change.
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