蒸散分离的玉米水分利用效率变化及影响因素 postprint

Abstract: Water use efficiency (WUE) is an important indicator of the carbon- water cycle of farmlandecosystems and is of great significance for guiding agricultural irrigation and improving water productivity.Ningxia Irrigation area is a large-scale irrigation district located in the arid climate zone of China, where the cornplanting area is the largest. Based on eddy flux observation of actual evapotranspiration (ET) of farmlandecosystems, this paper used the hydrogen and oxygen stable isotope method to segment evapotranspiration andestimated the total primary productivity (GPP) of typical maize farmland ecosystems in the Yellow Riverirrigation area of Ningxia using the LUE (Light Use Efficiency) model. Population Water Use Efficiency WUET =GPP/T, Ecosystem Water Use Efficiency WUEET = GPP/T, and Intrinsic Water Use Efficiency IWUEVPD = (GPP·VPD)/ET were calculated. Then, the relationship between different WUE and environmental factors, such as airtemperature, saturated water vapor pressure difference, CO2 concentration, effective photosynthetic radiation, andsoil water content was analyzed from three aspects: functional response relationship, correlation, and sensitivity.The result showed that the variation of actual evapotranspiration in the growing season of the maize agroecosystemin the Ningxia yellow irrigation area was single- humped, and the trends of crop transpiration andactual evapotranspiration were consistent. The variation of water use efficiency in the growing season wasdifferent among the three species, with WUET showing a“W-shaped”variation pattern during the growing seasonwhile WUEET and IWUEVPD showed a“single-hump”variation pattern. All three WUE peaks occurred at the maletasseling stage, reaching (5.90 kg C·m−3·H2O, 5.02 kg C·m−3·H2O, 32.9 kg C·hPa·m−3·H2O) respectively. Thethree kinds of water use efficiency began to decrease in the late filing period, and WUET increased slightly in thelate ripening period due to weak transpiration. Among the five environmental factors, WUET, WUEET andIWUEVPD were positively correlated with soil water content, and the correlation and sensitivity were the strongest.The three water use efficiencies were significantly negatively correlated with VPD, with the second strongestcorrelation and sensitivity. Air temperature, photosynthetically active radiation, and CO2 concentration werenegatively correlated with the three kinds of WUE but not critical factors. Therefore, soil moisture and VPD arethe key factors affecting the WUE of the maize farmland ecosystem in the Yellow River irrigation area of Ningxia.