Submitted to: International Journal of Remote Sensing
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/4/2007
Publication Date: N/A
Citation: Interpretive Summary: Energy fluxes and land surface parameters from two adjacent pastures under different management (heavy and moderate grazing density) practices were estimated with Landsat Thematic Mapper (TM) and Enhanced Thematic Mapper Plus (ETM+) remote sensors using the surface energy balance approach. Comparisons of the energy fluxes and land surface parameters were made. The goal was to compare the energy fluxes and land surface parameters from the two pasture fields as a function of grazing density. The effects of pasture grazing density in the partitioning of the energy flux and land surface parameters were estimated. The heavily grazed pastures showed higher sensible heat, emissivity, and surface temperature than the moderately grazed pastures mainly because of the limited vegetation cover, which plays an important role in the interception and reflectance of the incoming solar radiation. Vegetation also cools the land surface and hence reduces the surface temperature by increasing soil evaporation and vegetation transpiration. These results provide mechanistic information regarding the functioning of grazingland ecosystems.
Technical Abstract: A remote sensing-based land surface characterization and flux estimation study was conducted using Landsat data from 1997 to 2003 on two grazing land experimental sites located at the Agricultural Research Services (ARS), Mandan, North Dakota. Spatially distributed surface energy fluxes [net radiation (Rn), soil heat flux (G), sensible heat (H), latent heat (LE)] and surface parameters [emissivity (e), albedo (a), normalized difference vegetation index (NDVI) and surface temperature (Tsur)] were estimated and mapped at a pixel level from Landsat images and weather information using the Surface Energy Balance Algorithm for Land (SEBAL) procedure as a function of grazing land management: heavily grazed (HGP) and moderately grazed pastures (MGP). Energy fluxes and land surface parameters were mapped and comparisons were made between the two sites. Over the study period, H, e, and Tsur from HGP were higher by 6.7%, 8.2%, and 2.9% than in MGP, respectively. The study also showed that G, LE, and NDVI were higher by 1.3%, 1.6%, and 7.4% for MGP than in HGP, respectively. The results of this study are beneficial in understanding the trends of land surface parameters, energy and water fluxes as a function of land management.