A Directional Change in the Subalpine Forest-Heath Ecotone in Garibaldi Park, British Columbia

Abstract

In the northwestern portion of Garibaldi Park, British Columbia, often called the Black Tusk meadows area, a dozen glaciers and glacierets have been retreating fairly steadily for one hundred years or more (Mathews 1951, Figs. 1 and 2). The glaciers were advancing several centuries ago and overwhelmed forest, remnants of which are found today on the newly bared soil (Taylor 1936). Evidence for recent climatic change here, as in many other parts of the world, is therefore conclusive. It is difficult to implicate specific factors of climate in glacier retreat and advance although Mathews (1948), Hubley (1956) and Harrison (1956) have recorded some significant data relative to temperature changes in the Pacific Northwest. Obviously the snow remaining at the end of each summer in the glacier catchment basins must be a prime integrant of the high mountain climate of the Pacific slope. Post-Pleistocene changes in plant communities of the Pacific Northwest have been recorded by Hanson (1947). Despite the evident climatic shift over the last century, its expression in extant plant communities is not easy to discern. However, modest establishment of subalpine trees in heath in the Black Tusk area of Garibaldi Park appears to be attributable to the recent climatic shift, and a change in the snow pack, particularly, appears to be implicated in the vegetational change just as it is in the waning of the nearby glaciers. Although the impression is gained that the subalpine forest-heath ecotone is dynamic quite generally over the heavy snowfall area of the Coast Mountains of British Columbia, sites where the influences of the many ecological variables can be objectively examined are few. The Black Tusk area is one of the more suitable for study.