Climate and disturbance regimes are expected to change profoundly in 21st century forests. Whether and where forests may succumb to projected trends and shift to different ecosystem states is poorly resolved but essential for anticipating both ecological and social consequences of climate change. Evaluating forest resilience to environmental change is an emerging field, often addressed conceptually, theoretically, or observationally at broad scales. Integrated approaches that combine experiments, observations, and simulations are rare but essential for identifying mechanisms that may underpin transitions to alternate states in forest ecosystems and for evaluating associated consequences. In this talk I will present a series of studies that explore the following question: How and why might warming-drying conditions and altered stand-replacing fire regimes catalyze changes in high-elevation and high-latitude conifer-forest ecosystems? In subalpine forests of Yellowstone National Park, the historical climate-fire context, current conditions, and expected trends provide a unique opportunity to address such questions. Climate and fire regimes have varied substantially in the past. Projections suggest, however, that by mid-21st century, fire and climate in these systems will likely exceed the most extreme conditions of the past 10,000 years. The presentation will emphasize research in Yellowstone and will conclude with some discussion on future research directions doing a regional comparison between Yellowstone and the boreal forest of interior Alaska. High latitude and high elevation conifer forests may look qualitatively different in coming years. This talk will attempt to begin painting a picture of how these ecosystems may change and why.