黑河中游灌区玉米农田蒸散涡度相关分析研究

Characteristics and Impact Factors of Evapotranspiration in Maize Field of Irrigation Area in Heihe Middle Reaches

农田蒸散是联系作物气孔行为、生态系统水分利用效率的重要生态过程,对农田合理灌溉有重要意义。根据涡度相关系统观测的黑河中游农田生态系统2012年生长季的蒸散数据与气象数据,分析了农田蒸散的日、季节变化,对环境影响因子与农田蒸散的关系进行研究。研究结果表明:试验地在玉米生长季,蒸散日变化呈现早、晚低,中午高的变化特征,但受当地气候影响,正午蒸散值有略微的下降,出现具有"蒸散高地"现象的"单峰型"变化曲线;蒸散最大日峰值出现在大喇叭口期,为0.32mm·h-1,最低日峰值出现在完熟期,为0.16mm·h-1。农田蒸散季节变化动态明显,与玉米叶面积指数密切相关,呈明显的单峰变化曲线,在抽雄吐丝期达到最高值(91.1mm),在完熟期达到最低值(33.0mm)。土壤温度是农田蒸散最主要的环境控制因子,光合有效辐射、空气温度、空气相对湿度、风速次之,土壤含水量的响应最弱。土壤温度、空气温度、风速和空气相对湿度对农田蒸散的影响主要是直接影响,光合有效辐射主要通过土壤温度和空气温度对农田蒸散产生影响。

Evapotranspiration （ET） is a key ecological process of linking crop stomatal behavior and water use efficiency in the ecosystem. The study of evapotranspiration has important meaning in water resource utilization, crop irrigation scheduling and the improvement of crop yield. An ecological experimental station of hydrological research on maize field was established in Zhangye Oasis in irrigation in Heihe middle reaches. ET and meteorological data was measured continuously in maize growth season （from May to October）in 2012 using the eddy covariance technique. The diumal and seasonal dynamics of ET and environmental impact factors influencing ET were analyzed. The results showed that the diumal variation of ET in this agroecosystem can be graphed as a line with a single-peak which occured high in the noon and low in the morning and evening as following the growing stage; while ET declined slightly and a plateau in the evapotranspiration occured during the middle part in the day affected by local climate. Seasonal ET highest peaked in bell-mouthed period （0.32 mm·h^-1） and lowest peaked in maturity period （0.16mm·h^-1）. ET seasonal change was obvious and ET dynamics were closely linked to the irrigation, seasonal distribution of precipitation and Leaf area Index of maize. Seasonal ETpeaked in Tasseling-Silking stage with 91.1mm and reached the lowest 33mm in Maturity stage. Soil temperature （Ts） was the major environmental factor controlling ET in this agroecosystem, followed by photosynthetically active radiation （PAR）, air temperature （Ta）, relative air humidity （RH） and wind speed （Ws）. Soil water content （0） had no significant influence on seasonal variation of ET. Ts,Ta, Ws, RH affected ET directly, and PAR mainly through the influence of Ts and Taaffected ET.