基于不同时间尺度玉米蒸散蒸腾量及其影响因素

Evapotranspiration and Transpiration of Maize in Two Time Scales and the Environmental Effects

运用涡度相关仪、包裹式茎流计对半干旱区玉米蒸散和蒸腾进行连续观测,并对田间土壤水势及其周围气象因子进行同步监测,分析了玉米蒸散和蒸腾在不同时间尺度上的变化过程及其影响因素,结果表明:①涡度相关仪测定的日蒸散量和茎流计测定的日腾量变化规律一致,相关性较好,但日内蒸散速率和蒸腾速率的变化受环境因子的影响而呈现不同的变化特征;②不同深度土壤水分状况对玉米蒸散和蒸腾存在不同影响。对玉米蒸散起较大作用的是地表以下10~15cm深处的土壤水势,而对玉米蒸腾起较大作用的是15~20cm深处的土壤水势;③在不同时间尺度上,太阳辐射始终是影响玉米蒸散和蒸腾的最主要气象因子;但在日内变化上,玉米蒸散速率和蒸腾速率与太阳辐射和饱和水汽压差均存在较好的相关关系。

Maize is one of the major crops in semiarid areas in northwestern China. Correct estimation of maize evapotranspiration and a better comprehension of its water consumption characteristics will play a key-role in precision irrigation schedules because crop growth and yield are associated with water passing through the crop. Here,we measured evapotranspiration and transpiration of maize with an eddy covariance system and packaged sap flow gauges in a semi-arid area. Simultaneous meteorological factors and soil water potential at different depths were observed using minitype auto-meteorological stations and soil moisture sensors at an experimental station within an agro-ecosystem at Lanzhou University. Using field data,we compared evapotranspiration and the transpiration of maize and analyzed the correlation between environmental factors and evapotranspiration/transpiration values at two time scales. We found a good correlation between daily measurement results of eddy covariance and sap flow gauges,but diurnal variation has different characteristics due to environmental factors even though hourly-scaled evapotranspiration and transpiration have a good linear relationship. Soil water potentials at different depths have different contributions to evapotranspiration and transpiration.Evapotranspiration is mainly influenced by the soil water potential at 10~15cm under the surface,while transpiration is mainly affected by soil water potential at 15~20cm. However,correlation analysis shows that there are not strong relationships between soil water potential and evapotranspiration/transpiration because of the complex effects of various factors on soil water condition. A correlation was found between evapotranspiration/transpiration and solar radiation at different temporal scales,while diurnal variation in evapotranspiration and transpiration depends on solar radiation and vapor pressure deficits.