Over the last several decades, increasing wildfire activity across California has put the state’s communities and ecosystems at risk. Effective wildfire management is critical to achieving social and ecological goals, which include protecting public health and safety, the economy, and natural resources. However, wildfire management is complicated by uncertainties related to the amount and composition of fuels and emissions from California’s landscape fires.

In this dissertation, I explored some of the challenges to wildfire management in the Sierra Nevada mountains of California. By investigating fire growth, weather, firefighting resources, and damages during the 2021 fire season in the second chapter of this dissertation, I found that broad-scale weather caused extreme fire growth in multiple large fires at once in the Sierra Nevada, creating a strain on already-limited resources and influencing the magnitude and timing of damages from the fires. In my third chapter, I characterized the total carbon and radiocarbon (14C) composition of fine particulate matter (PM2.5) emissions from the 2021 KNP Complex Fire in the southern Sierra Nevada. I combined these observations with a Keeling plot approach and a box model to estimate the mean age of fuels that were combusted. I concluded that fuel buildup over several decades drove emissions in the KNP Complex Fire, supporting the idea that a legacy of fire suppression has contributed to increased fire severity in the Sierra Nevada by promoting the accumulation of fuels. For my fourth chapter, I estimated fuel consumption and characterized the composition of fuels and PM2.5 emissions for a prescribed (Rx) fire in the central Sierra Nevada in 2022 as part of the Smart Practices and Architectures for Rx Fire in California campaign. I found that larger-diameter dead fuels contributed significantly to total fuel consumption in the prescribed fire, indicating that prescribed fire in landscapes with similar fuel composition might result in elevated PM2.5 concentrations associated with the combustion of larger fuels. Further, agreement in the observed 14C signature of fire-emitted PM2.5 and the 14C signature estimated using my 14C and fuel consumption measurements provides confidence that 14C measurements of atmospheric PM2.5 in the background atmosphere near fire-affected areas could be used to evaluate the influence of prescribed fire on fuel composition.

Altogether, the results of my research provide insight into the potential for large wildfires to overwhelm fire suppression capacity, highlight the importance of effective wildfire management, and identify a method by which prescribed fire can be monitored.