Heterogeneous surfaces have significant effects on water and heat exchanges and great efforts have been made to understand these processes in the past several years. However, due to the complexity of agroforestry ecosystems, there are many controversial results: Some scientists reported that agricultural shelterbelts can reduce evapotranspiration, while other scientists reported the measured increase of evapotranspiration over such systems.
We are systematically studying the hydrological process and turbulent process over agricultural shelterbelt agroforestry ecosystems. We made several field measurements. We also extended our shelterbelt turbulent flow model to include heat and water transfer processes to study the mechanisms of water and heat exchanges affected by inhomogeneous turbulent flows. We find that soil moisture determines the pattern and direction of evapotranspiration over agroforestry ecosystems. When the soil is dry, the evapotranspiration is enhanced by inhomogeneous turbulent flows; when the soil is wet, the evapotranspiration is reduced by such inhomogeneous turbulent flows. We will systematically present our measurements and simulated results and characterize the patterns of water and heat exchanges over agroforestry ecosystems.