UC Berkeley

Drought, elevated temperatures, and extended fire seasons combine with high fuel loads to increase the scale and severity of wildfires in California. Many of these fires occur in the forested montane watersheds that provide approximately 60% of the developed water supply of the state, creating a critical nexus between water and fire from a management perspective. However, the links between hydrological and fire processes go well beyond a common dependence on forests. Both water and fire cycles are impacted by, and impact upon the growth, spread, function, and disturbance of vegetation communities. This means there are multiple processes linking plants, fire and water. With climate change projected to warm temperatures, reduce snowpack, extend fire seasons, and increase drought stress on Californian watersheds, foresters are turning to alternative forest management strategies. One such strategy involves the re-introduction of frequent mixed-severity fire into the landscape to lower fuel loads and reduce the risk of catastrophic fires. Co-benefits of this strategy are anticipated to include greater water yields and storage, and increased landscape diversity and forest resilience. In my primary study site of the Illilouette Creek Basin (in Yosemite National Park, California), this strategy has proven to be successful to date. Many important knowledge gaps remain, however, including how the strategy of re-introduce fire will impact the water cycle as climates warm, how transferable this strategy is to other basin, the potential implications of frequent burning on erosion and water quality, and how changes in water storage in fire-treated landscapes, and specifically in soil moisture, might modify the resulting fire regime. To answer these questions, this dissertation draws on satellite and field collected data, laboratory experiments, and hydrological and statistical modeling to explore fire-vegetation-water-climate feedbacks and inform future forest management in California.