The role of biotic interactions at alpine treeline

What determines the border between forest and meadows on mountains? Physiological constraints to upright woody growth under cold or snowy conditions are thought to drive the position of treeline on mountains. However, local-scale positive feedbacks between vegetation and microclimate can facilitate tree seedling recruitment, and thus, modify the position of treeline. We argue that these facilitative interactions may result in unexpectedly slow or fast changes in the position of treeline with warming, which must be accounted for in projections of range shifts under future climate change.