Climate Change as a Driver in Mountain Pine Beetle Outbreaks in Eastern Washington Washington State Climate Change Impacts Assessment Conference Seattle, Washington February 12, 2009 Elaine E. Oneil 1, Jeffrey A. Hicke 2, Donald McKenzie 3, and James A. Lutz 1 1 College of Forest Resources, University of Washington 2 Department of Geography, University of Idaho 3 Pacific Wildland Fire Sciences Lab, U.S. Forest Service

J. Hicke

Photo credit: Don Hanley

MPB and host as co-drivers of MPB epidemics with climate change  Host Susceptibility a function of changes in summer VPD  Linked to the likelihood of a tree, or stand, being attacked as a function of poor vigor.  Warmer and drier summers leading to increased moisture stress and reduced vigor within pine forests  Warmer and/or drier winters reducing snowpack and effective moisture retention into late spring/early summer  Risk of MPB attack linked to changes in annual temperature regimes  Linked to the likelihood of MPB attack as a function of MPB population dynamics and proximity to host trees  Climate change enhancing insect survival and reproduction at higher elevations and leading to asynchronous development at lower elevations

Acres affected by Mountain Pine Beetle in Washington StateYearYear Annual Acres (1000’s) affected by MPB in Eastern Washington Oneil, 2006

Mortality Rate = 2.2 TPA Mortality Rate 8.4 TPA

Adapted from Waring and Running (1998) Humidity 100% 60% 30% Vapor Pressure Deficit (VPD)

Climate predictors for MPB attack

Summer Water Deficit as a precursor to tree stress

Higher Elevations get hit harder Historical B MPB attacks

Adapted from: DeLucia, E. H., H. Maherali, et al. (2000). "Climate-driven changes in biomass allocation in pines." Global Change Biology 6(5):

MPB and host as co-drivers of MPB epidemics with climate change  Host Susceptibility a function of changes in summer VPD  Linked to the likelihood of a tree, or stand, being attacked as a function of poor vigor.  Warmer and drier summers leading to increased moisture stress and reduced vigor within pine forests  Warmer and/or drier winters reducing snowpack and effective moisture retention into late spring/early summer  Risk of MPB attack linked to changes in annual temperature regimes  Linked to the likelihood of MPB attack as a function of MPB population dynamics and proximity to host trees  Climate change enhancing insect survival and reproduction at higher elevations and leading to asynchronous development at lower elevations

Research Questions Do Tmax and Tmin increase in lock step? –future VPD’s are likely underestimated Improve predictions of Tdew in increasingly arid environments –future VPD’s are likely underestimated. Determine if, and how quickly, leaf area – sapwood area ratios might change in response to changing VPD –Keys into increasing vulnerability to MPB and likelihood of loss of the species altogether Will other phenotypes/genotypes of MPB invade low elevation sites

Blue Print for Management Action  Determine a stress index for lodgepole in their current niches  Refine estimates of future stress based on climate scenarios  Determine if LP can modify its LA/SA ratios in response to the change in VPD (aka research)  Determine how stand carrying capacity changes in response to climate shifts and manage stands to stay within the carrying capacity of the site Determine how habitat types will move and change in their constituency with climate change Determine how to model that change to increase forest ecosystem resilience  Refine our estimation of disturbance rates