Wildfires, climate change, and tree regeneration

A study suggests that a combination of climate change and wildfires could lead to abrupt loss of low-elevation forests. Climate change could contribute to abrupt ecosystem shifts by reducing trees' ability to regenerate after disturbances such as fires. However, the relationship between annual and seasonal climate conditions and tree regeneration is poorly understood. Kimberley Davis and colleagues examined the relationship between annual climate and postfire regeneration of two ecologically and economically important conifer species, ponderosa pine and Douglas fir, in low-elevation forests in western North America. The authors used tree rings to determine establishment dates of more than 2,900 trees that regenerated after fires in California, Colorado, the Northern Rockies, and the southwestern United States between 1988 and 2015. Annual regeneration rates exhibited a threshold response to seasonal climate conditions: summer humidity for ponderosa pine, maximum surface temperature for Douglas fir, and soil moisture for both species. Over the past 20 years, climate conditions have crossed these thresholds at the majority of study sites, leading to abrupt declines in how often annual conditions are suitable for tree regeneration. Additional fires in such sites might catalyze transitions from forest to nonforest ecosystems, according to the authors.

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Article #18-15107: "Wildfires and climate change push low-elevation forests across a critical climate threshold for tree regeneration," by Kimberley T. Davis et al.

MEDIA CONTACT: Kimberley T. Davis, University of Montana, Missoula, MT; tel: 401-787-7456; e-mail: kimberley.davis@umontana.edu; Philip E. Higuera, University of Montana, Missoula, MT; tel: 406-243-6337; e-mail: philip.higuera@umontana.edu; Solomon Z. Dobrowski, University of Montana, Missoula, MT; tel: 406- 243-6068; e-mail: solomon.dobrowski@umontana.edu

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