Vegetation change at high elevation: scale dependence and interactive effects on Niwot Ridge

Background: High-elevation mountain systems may be particularly responsive to climate change. Aims: Here we investigate how changes along elevation gradients in mountain systems can aid in predicting vegetation distributional changes in time, focusing on how changing climatic controls affect meso-scale transitions at the lower and upper boundaries of alpine vegetation (with forest and subnival zones, respectively) as well as micro-scale transitions among plant communities within the alpine belt. We focus on climate-related drivers, particularly in relation to climate change, but also consider how species interactions, dispersal and responses to disturbance may influence plant responses to these abiotic drivers. Results: Empirical observations and experimental studies indicate that changing climatic controls influence both meso-scale transitions at the upper and lower boundaries of alpine vegetation and micro-scale transitions among plant communities within tundra. Micro-scale heterogeneity appears to buffer response in many cases, while interactions between climate and other changes may often accelerate change. Conclusions: Interactions with microtopography and larger edaphic gradients have the capacity to both facilitate rapid changes and reinforce stability, and that these interactions will affect the responsiveness of vegetation to climate change at different spatial scales