Factors influencing soil moisture and plant community distributions on Niwot Ridge, Front Range, Colorado, USA.

Slope-aspect influenced evapotranspiration and soil desiccation in the Colorado alpine tundra via control over radiation and wind speed. Soil at the S-facing site dried faster than soil on other slopes of the knoll. Dryas octopetala prefers more moist northern slopes on Niwot Ridge, illustrating the importance of topoclimatic controls over soil moisture to vegetation distribution in the fellfield. Water relations during the growing season influence vegetation distribution within topographic depressions. Where meltwater is supplied throughout the growing season wet meadow and moist shrub tundra occur. Evapotranspiration from the wet meadow was 1.5 times greater than from other communities in the Saddle area during a drying period. Contrasts in snow cover depth between windward and leeward slopes is an important location factor for dry fellfield, dry meadow, moist meadow and snowbed vegetation.-from Author