Water And Carbon Fluxes Along An Elevation/Precipitation Gradient In A Sagebrush Steppe Environment

Abstract:

Environmental gradients exert controls on water, carbon and energy fluxes across montane landscapes, impacting the magnitude and timing of evapotranspiration, carbon uptake, water stress, and water use efficiency. Four eddy covariance systems were situated along an elevation gradient in Idaho’s Owyhee Mountains. The sites are part of the Reynolds Creek Critical Zone Observatory and contribute to an ongoing long-term environmental monitoring network in the USDA’s Reynold’s Creek Experimental Watershed. The sites include a Wyoming big sagebrush site, a low sagebrush site, a post-fire mountain big sagebrush site, and a mountain big sagebrush site located at elevations of 1425, 1680, 1808 and 2111 m. Variations in climate follow the montane elevation gradient; mean annual precipitation at the sites is 290, 337, 425, and 795 mm, respectively, and mean annual temperature is 8.9, 8.4, 6.1, 5.4°C. Transpiration peaked about a month earlier at the lower elevation sites, but with limited precipitation the vegetation also encountered water stress much earlier. The two higher elevation sites experienced relatively little water stress and transpired at near potential for most of the growing season. Implications on water use efficiency were investigated.