Comparison of Fluxes Over Sagebrush and Above and below An Aspen Canopy.

This study compares and contrasts the seasonal surface fluxes of sensible heat, latent heat and carbon measured over different vegetation in a rangeland mountainous environment within the Reynolds Creek Experimental Watershed.  Eddy covariance systems were used to measure surface fluxes over sagebrush, aspen and the understory beneath the aspen canopy.  Peak leaf area index of the sagebrush, aspen, and aspen understory was 0.8, 0.9, and 0.7, respectively.  The sagebrush and aspen canopies were subject to similar meteorological forces, while the understory of the aspen was sheltered from the wind.  Fluxes of latent heat and carbon for all sites were minimal through the winter.  Growing season fluxes of latent heat and carbon were consistently higher above the aspen canopy than from the other sites.  While growing season carbon fluxes were very similar for the sagebrush and aspen understory, latent heat fluxes for the sagebrush were consistently higher.  Higher evapotranspiration from the sagebrush was likely because it is more exposed to the wind.  Sensible heat flux from the aspen was very similar to that measured above the sagebrush, even though measured surface temperature of the sagebrush was consistently higher than that for the aspen canopy.  Larger surface roughness of the aspen canopy apparently compensated for its lower surface temperature.  Results from this study illustrate the influence of vegetation on the spatial variability of surface fluxes across rangeland landscapes.