How Do Bark Beetle Outbreaks, Tree Regeneration, and Climate Determine Fuel Treatment Longevity?

As climate change continues, forests are increasingly affected by multiple types of disturbances over short periods. Notably, outbreaks of bark beetles have been widespread and affect fire regimes in complex ways. While much research has examined how susceptibility to outbreaks depends, in part, on the same attributes that are manipulated by fuel treatments, less attention has been placed on how those outbreaks, in turn, affect the long-term efficacy of fuel treatments. Conversely, fire severity (which is modulated by fuel treatments) also affects susceptibility to outbreaks. Importantly, full accounting of the interactions among fuel treatments, outbreaks, and fires under an altered climate is lacking, setting the stage for unpredicted outcomes. Using the montane forests of the Sierra Nevada Mountain Range as a case study, this project seeks to understand: (1) effects of fuel treatment and climate on fire severity; (2) how post-treatment fires and bark beetle outbreaks interact to determine longevity of fuel treatments; and (3) how fuel treatments, fires, and bark beetle outbreaks interact to determine cumulative tree mortality, regeneration, and vegetation conditions. The study will model interactions among fuel treatments, fires, and bark beetle outbreaks under climate change scenarios.