Interannual water and heat exchanges over a rainfed maize agricultural ecosystem in different hydrological years

摘要

Latent heat (LE) and sensible heat fluxes (H) and environmental effects have been reported in many ecosystems, but little is known about how it changes and responds to environmental variables over maize agricultural ecosystem with long-term measurements. In this study, biological and environmental controls regulating variations of daily, seasonal and interannual water and heat exchanges over rainfed maize agroecosystem were determined by about three years’observation data from eddy covariance technique. The results showed that the relative contribution of radiation (ETeq) and surrounding environmental (ETat) terms to the total evapotranspiration (ET) were significantly distinct among the different hydrological years. Higher value of ETat and lower ETeq were found in dry year (2006). The decoupling coefficient (Ω) is an index of the relative importance of the controlling factors in the determination of ET, and low Ω (＜0.5) suggested that great importance of the atmospheric and surface factors in controlling ET. In this study, occurrence of Ω＜0.5 was 78.9％, demonstrating the evapotranspiration process is closely coupled to the surrounding atmospheric and surface factors, especially in the dry year. Those indicated that interannual variations in components of ET had been attributed to the changes in climate that affect precipitation, radiation between years.