Submitted to: Hydrology and Earth System Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/3/2010
Publication Date: 6/17/2010
Publication URL: http://parking.nal.usda.gov/shortterm/21524_Flerchinger-2010-HESS.pdf
Citation: Flerchinger, G.N., Marks, D., Reba, M.L. Yu, Q., Seyfried, M.S. 2010. Surface fluxes and water balance of spatially varying vegetation within a small mountainous headwater catchment. Hydrology and Earth System Sciences. 14:965-978. Interpretive Summary: Understanding the role of ecosystems in modulating energy, water and carbon fluxes is critical to quantifying the variability in energy, carbon, and water balances across landscapes. This study highlights the influence of vegetation and site conditions on surface energy, water and carbon fluxes across a small headwaters catchment. Differences in the surface energy, water and carbon fluxes between three sites were modulated by the characteristics of the three vegetation types: sage brush, aspen and aspen understory. Results from this study illustrate the influence of vegetation on the spatial variability of surface fluxes across mountainous landscapes, which scientists can capitalize upon to better describe and model these ecosystems and their response to climate change.
Technical Abstract: Understanding the role of ecosystems in modulating energy, water and carbon fluxes is critical to quantifying the variability in energy, carbon, and water balances across landscapes. This study compares and contrasts the seasonal surface fluxes of sensible heat, latent heat and carbon fluxes 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 low sagebrush (Artemesia arbuscula), aspen (Populus tremuloides) and the understory of grasses and forbs beneath the aspen canopy. Peak leaf area index of the sagebrush, aspen, and aspen understory was 0.77, 1.35, and 1.20, respectively. The sagebrush and aspen canopies were subject to similar meteorological forces, while the understory of the aspen was sheltered from the wind. Estimated cumulative evapotranspiratation from the sagebrush, aspen understory, and aspen trees were 399 mm, 205 mm and 318 mm. A simple water balance of the catchment indicated that of the 700 mm of areal average precipitation, 442 mm was lost to evapotranspiration, and 254 mm of streamflow was measured from the catchment; water balance closure for the catchment was within 7 mm. 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 tended to be slightly less than the sagebrush site during the growing season when the leaves were actively transpiring, but exceeded that from the sagebrush in May, September and October when the net radiation was offset by evaporative cooling. Results from this study illustrate the influence of vegetation on the spatial variability of surface fluxes across mountainous rangeland landscapes.