As the human population continues to grow and climate change progresses, stressors on ecohydrologic systems are exacerbated. Groundwater-dependent ecosystems such as freshwater springs are ecological hotspots supporting highly diverse habitats yet are understudied and, in most places, eradicated via human development. Our forested mountain systems and subsequent water supplies are also facing shifts in their structure, functionality, and succession. With the intensity and frequency of forest fires increasing and snowpack declining in the western United States, a common question has become how can we reduce forest fire risk while increasing watersheds efficiency at generating water supplies? The link between these two topics is a need for management through an ecohydrologic lens that provides a holistic approach to preserving our natural resources. Using Mt. Tamalpais, located in Marin County in northern California, we evaluated the effectiveness of an adapted springs ecosystem assessment protocol (A-SEAP) at characterizing springs geophysical properties and identifying aggregate areas of concern. The second portion of this dissertation evaluated the hydrologic response to forest fire mitigation in the Ashland watershed of southern Oregon. The third portion of this work included modeling scenarios of the hydrologic response to forest fire mitigation strategies in order to inform land managers on thresholds needed to increase surface runoff from vegetation removal. A-SEAP demonstrated that most springs in this region have fair ecohydrologic integrity relative to other spring studies, with a mean value of 3.62 out of 6. A-SEAP indicators identified springs located in Mt. Tamalpais State Park as lower ecohydrologic integrity than springs in the protected Marin Municipal Water District. A-SEAP indicators also successfully identified springs in need of restoration that fit the goals of the local land management agencies. In Ashland, despite cumulatively treating roughly 15% and 20% of the basins, these treatments only represent a decrease in canopy cover at the watershed scale of 3% and 4%, in the West and East sub-basins in the Ashland watershed, respectively. We found that in the post-treatment period, the West and East basins experienced an average annual water yield decline of 26% and 24%, respectively, with 66% (West) and 72% (East) of the changes in water yield attributed to annual variations in precipitation. Our modeling efforts in the Ashland basin demonstrated that treatments with at least 25% of the watershed treated with a basal area reduction exceeding 25% led to a significant increase in annual water yield over low, average, and above average water years. We also found that treatment intensity plays a larger role than area treated. A scenario with 25% of the watershed experiencing a 75% reduction in basal area had significantly higher annual water yields as compared to a treatment of 75% of the watershed with a 25% reduction in basal area. This dissertation provides methodologies and insights into how to best manage landscapes undergoing a change from both anthropogenic and natural stressors. This novel research presents a framework to develop holistic, ecohydrologic land management strategies that ensure climate resilient ecosystems and water supplies for our future generations.
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