江淮流域稻麦轮作蒸散特征及其影响因子

Characteristics of Evapotranspiration and Its Influencing Factors in Rice-wheat Rotation in the Jianghuai River Basin

蒸散(ET)是水分交换的重要过程,对理解地表水平衡至关重要。基于安徽省寿县国家观测站多年的通量和气象数据,分析了江淮流域稻麦轮作作物ET变化特征,并利用通径分析方法分别对冬小麦和水稻ET的影响因子进行辨识。结果表明:①江淮流域稻麦轮作田多年均ET年总量为740.3 mm,其中冬小麦、水稻、裸地分别占比40.7、52.3、7.0。冬小麦ET的日均值为1.40 mm/d,在生长季内ET变化表现为弱“双峰型”特征,两峰值分别位于出苗-三叶和开花期。水稻ET的日均值为3.23 mm/d,在生长季内ET变化表现为“单峰型”,峰值位于拔节期。②冬小麦ET主要受净辐射(R-n)和叶面积指数(LAI)影响,R-n的直接作用最明显,而LAI主要通过R-n路径对ET产生间接影响。水稻ET主要受R-n和20 cm土壤体积含水量(VSWC-20)影响,R-n直接作用更明显。对比两种作物,R-n对其ET都起决定性作用,LAI对冬小麦ET作用明显高于水稻,而VSWC-20对水稻ET促进作用明显,对冬小麦ET变化促进作用可以忽略。

Actual evapotranspiration(ET)is an important process for water exchange and is critical to understanding surface water balance.Based on the flux and meteorological data of Shouxian National Observatory of Anhui Province for many years,this paper analyzed the characteristics of ET changes in rice-wheat rotation crops in the Jianghuai River Basin,and identified the ET influencing factors of winter wheat and rice by using path analysis methods.The results showed that:①the annual average total ET of rice-wheat rotation fields in the Jianghuai River Basin was 740.3 mm,in which winter wheat,rice,and bare land accounted for 40.7%,52.3%,and 7.0%,respectively.The daily average ET of winter wheat was 1.40 mm/d.During the growing season,the change of ET showed a weak“double-peak type”characteristic.The two peaks were at the emergence-three-leaf and flowering stages.The daily average ET of rice was 3.23 mm/d,and the change of ET during the growing season was a“single peak type”,and the peak value was at the jointing stage.②ET of winter wheat was mainly controlled by net radiation(Rn)and leaf area index(LAI).The direct effect of Rn was the most obvious,while LAI had an indirect effect on ET mainly through the Rn path.ET of rice was mainly controlled by Rn and 20 cm soil volumetric water content(VSWC20),and the direct effect of Rn was more obvious.Comparing the two crops,Rn had a decisive effect on ET,LAI had a significantly higher effect on ET in winter wheat than rice.VSWC20 had a significant promotion effect on ET in rice,but it could be ignored in promoting ET change in winter wheat.