黄土塬区麦田蒸散特征

利用大型称重式蒸渗仪研究了黄土塬区冬小麦不同时段单元（生育期、月、日、时）的蒸散特征，并分析了叶面积指数、土壤含水量和气温、降水等因子对蒸散的影响.结果表明，在试验年份，各生育期内冬小麦的日蒸散量:孕穗 抽穗期﹥开花期﹥起身期﹥拔节期﹥灌浆期﹥返青期﹥成熟期﹥越冬期；生长前期蒸散受温度影响较大，中期受叶面积指数影响较大，后期土壤水分成为蒸散的限制因子，灌浆期内冬小麦日均蒸散量因受土壤水分亏缺影响而显著下降，日均蒸散量从孕穗 抽穗期的625 mm·d^-1 减小到灌浆期的2.66 mm·d^-1；月蒸散以4～6月最高，3个月蒸散量占试验期间总蒸散量的80％以上；麦田逐日蒸散变化曲线上的波动峰值反映了受降水作用土壤水分状况改善条件下的蒸散特征；时蒸散过程在总体遵循周期性的前提下表现出随天气而改变的现象.

Evapotranspiration of winter wheat field on Loess Plateau tableland

This paper measured the evapotranspiration (ET) rate of a winter wheat field on the Loess Plateau tableland by using large-scale weighing lysimeter, and analyzed the effects of wheat leaf area index (LAI) , soil water content, air temperature, and rainfall on the ET at the time scales of growth stage, month, day, and hour. The results showed that the mean daily ET rate in different growth stages was in the order of booting-heading > flowering > erecting > jointing > filling > reviving > ripening > overwintering. Air temperature had a larger effect in initial stage, LAI was in mid stage, and soil water content was in last stage in the experimental year. The mean daily ET rate was markedly decreased from 6.25 mmn x d(-1) at booting-heading stage to 2.66 mm x d(-1) at grain-filling stage due to soil water deficit. The monthly ET rate in April, May and June was higher than that in other months, and the ET amount of the three months accounted for 80% of the total during the experimental period. The apices of daily ET curve mainly reflected the effects of rainfall, and the hourly ET process basically reflected the ET changes with weather conditions.