GLOBAL CHANGE AND WHITEBARK PINE: RESTORATION, REFUGIA, AND ALPINE TREELINES

Whitebark pine is a major component of subalpine forests in western North America. The species occupies harsh high-mountain sites up to treeline, where it is often the dominant species. The species is ecologically important but is also a valuable species for studying the dynamics of alpine treelines. However, whitebark pine has experienced significant mortality in recent decades from mountain pine beetle outbreaks and white pine blister rust. This kind of rapid environmental change presents significant challenges to our understanding and management of the dynamics of ecological communities. On one hand, the effects of climate change on forest ecosystems could provide unique opportunities to study how species, populations, communities, and ecosystems respond to large-scale disturbance. On the other, prediction of future ecosystem behaviors and associated management decisions are complicated by a current lack of understanding of long-term dynamics. Managers are responding to indirect effects of climate change by expanding restoration activities into previously unmanaged, and often poorly understood, forest ecosystems. In this dissertation I investigated three aspects of whitebark pine ecology and conservation: 1) the ecological responses of whitebark pine stands to restoration treatment, 2) the potential of treeline habitats as refugia from mountain pine beetle attack, 3) and the climate-related processes that control growth form at treeline