| Summary: | The alpine treeline ecotone in Glacier National Park (GNP) can respond to climate change. An examination of what is known about treelines in general indicates that seedling establishment is the important response to climate change, but this stage is also affected by many other variables. In GNP, the importance of protected sites generated by local geomorphic processes is closely connected to microclimate. Once seedlings are established, positive feedback is generated and tree species can advance rapidly. Feedback creates nonlinear relations in the response of vegetation to climate and so decouples the response to climate at least in rate. Then protected sites can become fully occupied during periods of rapid response driven by feedback but less available immediately thereafter even if the climate continues to ameliorate. The response that we see in GNP indicates that specific conditions in time and space – the historically contingent and the local – can outweigh generalities about ecotones.
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