Subjects: Agriculture, Forestry,Livestock & Aquatic Products Science >> Soil Science submitted time 2023-08-25 Cooperative journals: 《干旱区研究》
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.
Subjects: Geosciences >> Geography submitted time 2019-11-15 Cooperative journals: 《干旱区地理》
Abstract：采用K-means聚类分区，Sen’s斜率估计，Kendall-Tau非参数检验等方法，分析和讨论了近半个世纪（1960—2015年）我国西北地区不同区域的气温变化特征。发现近半个世纪西北地区气温保持了持续的显著上升，年均最低气温上升速率高于年均气温和年均最高气温。从空间的角度来看，新疆北疆地区的东北部，内蒙古北部、西部中东部，甘肃中部、西部，青海北部、中部，宁夏中部、北部地区以及陕西北部是升温最快的区域。虽然西北地区气温总体是上升趋势，但在时间上并不均匀一致。从1998年开始，西北地区气温升温减缓，部分地区出现了下降趋势。近半个世纪西北地区季节气温与年际气温变化趋势并不一致，变暖减缓在该地区不同季节的响应不同。1998—2015年，冬季是增温幅度最小的季节，多数子区冬季存在升温趋势减缓，甚至转为下降趋势。
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