UC Davis

Mitigating the effects of massive wildfires is one of the most critical forest conservation goals of our generation, and perhaps the most important in western North America. Changes in climate and Euro-American fire suppression have altered the natural fire regime across the western US. Chaparral-dominated ecosystems that historically experienced infrequent high-intensity fire are currently threatened by an increase in wildfire frequency driven by increased urbanization of wildlands, warming temperatures, and invasion of non-native species. Dry conifer forests, on the other hand, are experiencing fewer fires due to fire suppression policies, but these policies have resulted in fuel accumulations and forest densification. The warming climate is leading to drier fuels and more severe fire weather, and when fires escape control today, they tend to burn large areas at high severity, which pose enormous threats to biodiversity, human health, and the economy. To address these issues, fuel treatments such as prescribed fire, hand thinning, and mechanical surrogates for fire (e.g thinning, mastication) have been implemented to restore forest resilience by reducing surface and canopy fuels and restoring natural disturbance processes in historically frequent-fire forests. In my first chapter of this dissertation, I examined the impact of increased fire frequency on the composition and abundance of herbaceous and woody species in chaparral plant communities in the Interior Coast Range of northern California. In my second chapter, I document and analyze patterns in fuel dynamics after fuel treatments across dry conifer forests in the western US using 1,932 observations from 65 published studies. My third chapter concludes this dissertation by quantifying the current effectiveness of prescribed fire as a management strategy by documenting changes in surface fuel loading, stand structure, and resulting species diversity. Understanding the ecological consequences of human-driven changes to fire regimes, and the consequent management strategies to combat them, are crucial for projecting future fire activity under various climate change scenarios and land management strategies.