A Comparative Analysis of Net Radiation and Evapotranspiration in Cropped vs. Old Growth Communities

He, C.

Presented at the All Scientist Meeting (1999-07-20 to 1999-07-21 )

Accurate assessment of the distribution of heat and water vapor fluxes in the land surface-atmosphere system is crucial to hydrological studies, large scale vegetation mapping and climate modeling. At the regional scale the effect of intensive management practices on heat and water vapor distribution in the surface-atmosphere system is not well understood. A preliminary study is being initiated to evaluate the effect of intensive management practices on heat and water vapor transfer in cropped vs. old growth communities at Michigan State University ’s Kellogg Biological Station.In-situ measurements of air, soil, and surface temperatures have been collected in corn, soybean, and alfalfa fields, grassland and forest sites since 1997. Additional parameters to be collected include surface reflectance, thermal radiation, wind speed and soil heat flux. These data will be used to analyze the heat and water vapor distribution in cropped and native forest communities by the surface energy balance equation, and the Bowen Ratio and Penman-Monteith methods.Contingent on the available funding, the long term goals of this study are to: (1) determine the spatial and temporal distribution of net radiation and ET in selected habitats at the KBS LTER site , (2) examine the relationships between net radiation, ET, and above ground net primary productivity (ANPP) in the cropped and old growth forest communities, and (3) compare the distribution of heat and water vapor fluxes in the land surface-atmosphere system in crop system representing high management and old growth forest representing low management. These results will improve our understanding of the heat and water vapor distribution in the Great Lakes agricultural ecosystems and will lead to reduced uncertainties in measuring, mapping and modeling vegetation under variable hydrological and climate systems.

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