A substantial upward shift of the alpine treeline ecotone in the southern Canadian Rocky Mountains

Abstract

Changes within and beyond the alpine treeline ecotone are hypothesized to respond to climatic changes and to be controlled by site-specific conditions. Repeated photographs show significant changes in the alpine treeline ecotone of Goodsir Pass in Kootenay National Park, B.C. over the past century. Field work revealed increases in tree density within the ecotone, and a 150 vertical metre increase in the elevation of the ecotone, at a rate of 2.2 metres/year. Change within the ecotone of Goodsir Pass is more closely related to temporal climatic variability than to site-specific spatial variability. Repeated photographs from three National Parks in the southern Canadian Rocky Mountains show this change to be a typical but dramatic example. Results at several scales indicate that the occurrence, magnitude and type of change in the alpine treeline ecotone and the drivers of that change are most influenced by the regional ecologic and geo-climatic setting or context.