What Burns and What Returns: Multi-Scale Consequences of Unprecedented Fire Regimes in the Sierra Nevada

Abstract

Unprecedented wildfire and climate change are altering landscapes in the Sierra Nevada at rates and extents that challenge the capacity of both ecosystems and communities to recover. Increasingly large and severe wildfires are pushing vegetation and inhabited communities beyond sustainable thresholds, raising concerns about managing these systems under more extreme future conditions. High uncertainty associated with changing fire regimes presents substantial challenges for land managers and community planners. This dissertation addresses three scales where uncertainty is greatest. In my first chapter, I synthesize literature to analyze broad vegetation transitions across conifer, oak, shrub, meadow, and grassland communities in the Sierra Nevada. Limited research on non-coniferous ecosystems has created a bias in which vegetation types more readily adapted to unprecedented fire and climate are often overlooked. In the second chapter, I focus on lesser studied systems of oaks and shrubs alongside conifers, where I use airborne lidar datasets to map their post-fire extents in Yosemite National Park. The resulting maps show where each type is establishing long-term following high severity fire and reveal how novel fire regimes and climate patterns are driving compositional reorganization away from conifer dominance. In my final chapter, I move into the realm of human infrastructure, where extreme fires are causing significant housing loss in the wildland urban interface. I use lidar to measure parcel-scale fuel cover and how it interacts with multiple confounding variables to determine the survival or destruction of homes in the wildland urban interface. This interdisciplinary approach to measuring the effects of extreme fire was driven by a unifying question across all three scales: what burns and what returns?