Climate change implications for conifer distribution and water resources management in the eastern Sierra Nevada, California

No environmental concern is as global, yet at the same time as local, as anthropogenic climate change. While most climate models still project with the most confidence at the global scale, impacts of climate change will be felt and dealt with regionally and locally. Global climate change, through increases in temperatures and changes in water cycling, will impact plant species distributions and water resources management. In the eastern Sierra Nevada region of California, such changes will have implications for invasive species and fire management, fisheries and recreation, water availability for local communities, and water exports to Los Angeles. This dissertation addresses these issues through an interdisciplinary examination of conifer establishment and seedling physiology at a low-elevation treeline and water resources management for one eastern Sierra community. In Chapter 1, I explore the establishment dynamics of a dominant conifer, Pinus jeffreyi , at the conifer forest-sagebrush steppe ecotone near Mammoth Lakes, CA. This research consisted of planting P. jeffreyi seedlings at two sites at and below the ecotone over three years and monitoring survival. The results from this study demonstrate the importance of growing season length, soil moisture, and microhabitat niches for successful P. jeffreyi establishment at the ecotone. Chapter 2 presents a greenhouse-based study of the effects of soil moisture on P. jeffreyi and P. contorta seedling growth and physiology. In this study, P. jeffreyi and P. contorta seedlings tolerated up to eight weeks without water before exhibiting reduced stem diameter growth and stem water potential. Additional soil water availability did not produce any positive effect on seedling growth or physiology. Chapter 3 is a case study of potential climate change impacts for the community water system in Mammoth Lakes, CA. I develop a series of snow water equivalent scenarios for the Mammoth Lakes area based on projections of decreased snow pack throughout California. I then explore implications of such changes for water availability in Mammoth Lakes and examine several adaptation strategies for ensuring continued water supply for the town and for Los Angeles. Overall, this dissertation points to the benefits of studying and managing climate change impacts and adaptation on a local scale.