Warming increased bark beetle-induced tree mortality by 30% during an extreme drought in California
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States); North Carolina State University, Raleigh, NC (United States)
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
- University of Minnesota, Minneapolis, MN (United States)
- University of California, Berkeley, CA (United States)
- USDA Forest Service, Davis, CA (United States)
- University of California, Irvine, CA (United States)
- Natural Resources Canada, Victoria British Columbia (Canada)
- University of California, Los Angeles, CA (United States)
- Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
- Utah State University, Logan, UT (United States)
- North Carolina State University, Raleigh, NC (United States)
Quantifying the responses of forest disturbances to climate warming is critical to our understanding of carbon cycles and energy balances of the Earth system. The impact of warming on bark beetle outbreaks is complex as multiple drivers of these events may respond differently to warming. Using a novel model of bark beetle biology and host tree interactions, we assessed how contemporary warming affected western pine beetle (Dendroctonus brevicomis) populations and mortality of its host, ponderosa pine (Pinus ponderosa), during an extreme drought in the Sierra Nevada, California, United States. When compared with the field data, our model captured the western pine beetle flight timing and rates of ponderosa pine mortality observed during the drought. In assessing the influence of temperature on western pine beetles, we found that contemporary warming increased the development rate of the western pine beetle and decreased the overwinter mortality rate of western pine beetle larvae leading to increased population growth during periods of lowered tree defense. We attribute a 29.9% (95% CI: 29.4%–30.2%) increase in ponderosa pine mortality during drought directly to increases in western pine beetle voltinism (i.e., associated with increased development rates of western pine beetle) and, to a much lesser extent, reductions in overwintering mortality. These findings, along with other studies, suggest each degree (°C) increase in temperature may have increased the number of ponderosa pine killed by upwards of 35%–40% °C-1 if the effects of compromised tree defenses (15%–20%) and increased western pine beetle populations (20%) are additive. Due to the warming ability to considerably increase mortality through the mechanism of bark beetle populations, models need to consider climate's influence on both host tree stress and the bark beetle population dynamics when determining future levels of tree mortality.
- Research Organization:
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
- Sponsoring Organization:
- USDOE; Pacific Southwest Research Station Climate Change; North Carolina State University
- Grant/Contract Number:
- 89233218CNA000001
- OSTI ID:
- 1969229
- Report Number(s):
- LA-UR-20-30376
- Journal Information:
- Global Change Biology, Journal Name: Global Change Biology Journal Issue: 2 Vol. 28; ISSN 1354-1013
- Publisher:
- WileyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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