loading page

Bark beetle effects on fire regimes depend on underlying fuel modifications in semiarid systems
  • +7
  • Jianning Ren,
  • Erin Hanan,
  • Jeffrey Hicke,
  • Crystal Kolden,
  • John T Abatzoglou,
  • Christina Tague,
  • Ryan Bart,
  • Maureen C Kennedy,
  • Mingliang Liu,
  • Jennifer Adam
Jianning Ren
University of Nevada, Reno

Corresponding Author:[email protected]

Author Profile
Erin Hanan
University of Nevada, Reno
Author Profile
Jeffrey Hicke
University of Idaho
Author Profile
Crystal Kolden
UC Merced
Author Profile
John T Abatzoglou
University of California Merced
Author Profile
Christina Tague
University of California, Santa Barbara
Author Profile
Ryan Bart
UC Merced
Author Profile
Maureen C Kennedy
University of Washington
Author Profile
Mingliang Liu
Unknown
Author Profile
Jennifer Adam
Washington State University
Author Profile

Abstract

Although natural disturbances such as wildfire, extreme weather events, and insect outbreaks play a key role in structuring ecosystems and watersheds worldwide, climate change has intensified many disturbance regimes, which can have compounding negative effects on ecosystem processes and services. Recent studies have highlighted the need to understand whether wildfire increases or decreases after large-scale beetle outbreaks. However, observational studies have produced mixed results. To address this, we applied a coupled ecohydrological-fire regime-beetle effects model (RHESSys-WMFire-Beetle) in a semiarid watershed in the western US. We found that surface fire probability and fire size decreased in the red phase (0-5 years post-outbreak), increased in the gray phase (6-15 years post-outbreak), and depended on mortality level in the old phase (one to several decades post-outbreak). In the gray and old phases, surface fire size and probability did not respond to low levels of beetle-caused mortality (<=20%), increased during medium levels of mortality (>20% and <=50%), and remained elevated but did not change with mortality (during the gray phase) or decreased (during the old phase) when mortality was high (>50%). Wildfire responses also depended on fire regime. In fuel-limited locations, fire typically increased with increasing fuel loads, whereas in fuel-abundant (flammability-limited) systems, fire sometimes decreased due to decreases in fuel aridity. This modeling framework can improve our understanding of the mechanisms driving wildfire responses and aid managers in predicting when and where fire hazards will increase.