Detecting Global Change at Alpine Treeline: Coupling Paleoecology with Contemporary Studies

Mountain ecosystems provide unique opportunities to detect and understand global change impacts due to their strong altitudinal gradients coupled with the presence of parks and biosphere reserves in many mountain areas where direct human impacts are minimal (Graumlich 2000; Becker and Bugmann 2001). Alpine treeline, the distinctive boundary between forest and tundra on high mountains, has been a particularly important focus of this research. While alpine treeline can appear to be a simple ecotone and thus a ready indicator of changing temperatures, a rich history of research has revealed that the dynamics of treeline are complex. Issues of lags and inertia, as well as multiple drivers across diverse scales abound. In this essay, we outline key issues for understanding alpine treeline in the context of global climate change. While our views strongly reflect research that has been done in the temperate zone, particularly in North America, the questions underlying the interpretation of treeline are applicable to many biotic indicators of climate change.