Environmental Controls on Turf-Banked Terraces

Turf-banked terraces in the alpine tundra of Glacier National Park, Montana, are typically characterized by alternating stripes of flat, stone-covered treads or steps and angled risers covered by alpine tundra vegetation. Previous research has suggested that the presence of turf-banked terraces is controlled by local environmental settings, particularly, topographic conditions. In this research, regression analysis is used to assess the correlations between turf-banked terrace characteristics and a set of hypothesized environmental controls. Measures of turf-banked terraces include the widths and standard deviations of treads, risers, and all stripes measured at 55 areally distributed 50-m field transects; the ratio of riser width to tread width; and a set of four one-dimensional pattern metrics that assess the spatial structure of the tread/riser sequences. These measures were derived using a run-length approach for field transects distributed in basins located throughout the eastern side of the Continental Divide. The environmental variables, generated from a 10-m spatial resolution digital elevation model (DEM), include elevation, slope angle, slope aspect, slope curvature, and soil moisture potential. Our results show that several turf-banked terrace characteristics are significantly correlated with individual environmental variables; stronger relationships are found when turf-banked terrace characteristics are related to transformed (i.e., principal components analysis) environmental variables using multiple regression analysis