Assessing historic change in subalpine forest : a case study in the West Castle Watershed

Abstract

Alpine treeline ecotone (ATE) is a dynamic region where tree growth is limited by atmospheric temperature. Landscape scale variation in climate, topography, and disturbance regimes cause heterogeneity in the ATE by suppressing tree elevation below the absolute thermal limit to growth. In order to understand how ATE will respond to anticipated atmospheric warming, observations of historic change are required. This research introduces a novel method of canopy cover observation using oblique historic imagery. ATE change is assessed in the West Castle Watershed between 1914-2006, and found to be correlated to elevation, aspect, and fire-exposure. A random forest model was used to test a spatial extension of observed canopy cover change into areas that were not observed in the oblique imagery. This model used proxies for climate, topography, and disturbance regime as predictive variables. Collectively, this thesis research demonstrates that oblique photography can provide valuable insights into dynamic processes in the ATE.