干旱区生态环境知识资源中心

The comparison of micrometeorological systems enables to analyze the reliability of the results and assess their adjustment to different crops. In the present study the evapotranspiration (ET) of a vineyard cover (Vitis vinifera) arranged in a trellis system was measured during its annual growth cycle by using the micrometeorological methods Bowen Ratio Energy Balance (BREB) and Eddy Covariance (EC). The research was conducted in 2007 in the semi-arid area of Tarazona de La Mancha, Spain. The main criterion of comparison between the systems was the daily and cumulative value of current ET. Once the closure of energy was forced, the BREB system overestimated the EC system fluxes in average values of 5 %. The differences can be explained by the close location of the lower arm of the plant cover in BREB system. Certain conditions of wind direction and atmospheric stabilty indicate higher requirements of the BREB method with respect to the selection of height and location of sensors on the cover. The location of the BREB system sensors in a heterogeneous cover like the vineyard should consider the impact of architecture on the homogeneity of the mixed layer. The analysis of the time evolution of the ET values and crop coefficient (Kc), which respond to crop development and high moisture because of irrigation or rainfall, increases reliability on the ET results obtained by the EC system with forced closure. The soil heat flux (G) presented different patterns due to lighting and shading of the soil providing different G/Rn values for the day (0.21) and night (0.68) periods.