中国南方农田蒸散量实测及其影响因素分析

利用基于闭路QCLAS-EC激光分析仪的涡度相关法对湖南省岳阳市郊区的一片蔬菜地的实际蒸散发、水汽通量以及潜热通量进行了连续两年的野外观测,并对原始观测数据进行处理,计算蒸散量,以分析研究区域实际蒸散量的年际尺度周期变化趋势和季节变化规律。结果表明,实验区域全年蒸散量在730~803 mm之间;季节变化大,8月达到全年最高水平3.5 mm/d,而1月只有0.4 mm/d。整个研究区域实测蒸散量变化规律是:春夏季较高,秋冬季较低;种植季较高,非种植季较低;每天的正午以及下午较高,夜晚较低。此外,利用高分辨率的实测工具观察不同的农业活动对实际蒸散的影响,发现种植引起蒸散发上升,收割引起蒸散发下降,并且收割使蒸散发下降的幅度要明显高于种植使蒸散发上升的幅度;灌溉对蒸散发有促进作用但是作用较小,施肥对蒸散发的影响目前尚不明确。

Study on in-situ evapotranspiration measurement and its influential factors in farmland in Southern China

Field observations for two consecutive years were carried out on the actual evapotranspiration, water vapor flux and latent heat flux(LE)for two consecutive years in the vegetable land in the suburb of Yueyang City, Hunan Province by using eddy covariance technique based on closed-path QCLAS-EC Analyzer. The original observation data were processed and the evapotranspiration was calculated so as to analyze the annual periodic change trend and seasonal variation law of the regional evapotranspiration. The results show that annual evapotranspiration in the study area were between 730 and 803 mm; the seasonal variation was substantial, reaching the highest level in August, 3. 5 mm/d and in January, only 0. 4mm/d. The actual evapotranspiration in the whole study area can be summarized as follows: higher in spring and summer, lower in autumn and winter; higher in planting season, lower in non-planting season; higher at midday and afternoon, lower at night. In addition, the effects of different agricultural activities on the actual evapotranspiration were observed by using high-resolution measured data. The findings are that the evapotranspiration was increased by planting and was decreased by harvesting, and the reduction of evapotranspiration by harvesting was significantly higher than that by planting. While irrigation also contributed to the promotion of evapotranspiration but was less pronounced, the effect of final fertilization on evapotranspiration was not yet clear.