B064-0015
Anthropogenic Warming Increased Ponderosa Pine Mortality by 20% During 2012-2015 Mega-drought in the Sierra Nevada.

Friday, 11 December 2020
Poster
Zachary Robbins, North Carolina State University Raleigh, Raleigh, NC, United States, Chonggang Xu, Los Alamos National Laboratory, Los Alamos, NM, United States, Rutuja Chitra-Tarak, Los Alamos National Laboratory, Earth and Environmental Sciences, Los Alamos, NM, United States, Christopher J Fettig, U.S. Forest Service, Pacific Southwest Research Station, Albany, CA, United States, Leif Mortenson, United States Forest Service Pacific Southwest Research Station, Davis, United States, Michael Goulden, Univesity of California, Irvine, Department of Earth System Science, Irvine, CA, United States, Devin W. Goodsman, Canadian Forest Service, Los Alamos, NM, United States, Gavin Dayanga Madakumbura, University of California Los Angeles, Atmospheric and Oceanic Sciences, Los Angeles, CA, United States, Lara M Kueppers, University of California Berkeley, Energy and Resources Group, Berkeley, CA, United States, Polly Buotte, University of California, Berkeley, Energy and Resources Group, Berkeley, CA, United States, Charlie Koven, Earth Sciences Division, Lawrence Berkeley National Laboratory,, Berkeley, CA, United States, Brian Aukema, University of Minnesota, St. Paul, United States, Alexander D Hall, University of California Los Angeles, Los Angeles, CA, United States and Robert Scheller, North Carolina State University, Forestry and Environmental Resources, Raleigh, NC, United States
Abstract:
During and immediately after the 2012-2015 drought in California, U.S., widespread mortality of trees occurred as tree defenses were weakened and they became susceptible to attack by bark beetles. Understanding these large-scale bark beetle epidemics requires formalizing interactions among beetle population dynamics, host tree stress, and tree population dynamics. Anthropogenic warming have been demonstrated in some systems to cause shift in the abiotic limits of beetles along with their host tree ranges and alters beetle population success and life stage synchrony. We sought to understand whether anthropogenic warming contributed to the tree mortality observed during and after the the 2012-2015 drought. We parameterized and simulated a model that combines western pine beetle (Dendroctonus brevicomis) phenology and attack dynamics with dynamics of tree defenses (Pinus ponderosa). We simulated four representative study areas in the Sierra Nevada for the years of 2006-2018. To understand the influence of temperature, we simulated both the observed temperature and a cooler temperature adjusted to historically observed means. We found that warming's influence on population levels of western pine beetle accounted for ~20% of tree mortality. Beetle populations at high elevations were reduced by as much as 50% under the historic/cooler temperature model. Our model attributes this to increased winter mortality, and decreased voltinism in certain years. Our results suggests that it is critical to consider insect populations to correctly assess the drought-caused tree mortality under a warming climate.
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