Stratifying Alpine Tundra for Geomorphic Studies Using Digitized Aerial Imagery

Abstract

In the alpine tundra zone of Niwot Ridge, Colorado Front Range, U.S.A., order of magnitude differences in surficial geomorphic process rates were found when the data were stratified by plant community. A two-stage classification technique to stratify vegetation units in the alpine zone for use in geomorphic studies is presented. In the first stage, spectral reflectance measurements from a digitized color infrared aerial photograph were used to classify general vegetation and cover classes on Niwot Ridge. This classification was able to distinguish between dry and moist meadow communities, scree slopes, and snowbed communities. A digital terrain model of Niwot Ridge was subsequently constructed to study the topographic influences on the distribution of alpine vegetation. The joint frequency distribution of alpine vegetation and elevation, slope, and aspect was estimated from previously mapped vegetation patterns, and the digital terrain model developed in the present study. In the second-stage classification, vegetation and other cover classes we reclassified based on the topographic distribution of vegetation and other cover classes such as fellfields. Surficial soil loss estimated from the present classification indicated that order of magnitude comparisons can be made between these estimates and those previously published.