Eco-geomorphic implications of hillslope aspect:: Inferences from analysis of landscape morphology in central New Mexico

We investigate the influence of hillslope aspect on landscape morphology in central New Mexico, where differences in soils, vegetation, and landforms are observed between mesic north-facing and xeric south-facing slopes. Slope-area and curvature-area relations, derived from a Digital Elevation Model (DEM), are used to characterize the opposing hillslope morphologies. In all geologies and elevation ranges studied, topographic data reveal significantly steeper slopes in north-facing aspects, and shallower slopes in south-facing aspects. North-facing slope curvatures are also greater than south-facing curvatures. Using a conceptual slope-area model, we suggest that for a given drainage area, steeper north-facing slopes imply lower soil erodibility. We argue that this interpretation, consistent with recent views of ecosystem control on semiarid erosion rates, shows the influence hillslope aspect on topography and its associated vegetation communities. Observed valley asymmetry in the region reinforces this concept and suggests a long-term legacy of aspect-modulated ecogeomorphic processes.