基于稳定同位素的覆膜灌溉农田SPAC水分传输机制与模拟

发布时间：2018-07-06 17:10

本文选题：稳定同位素 + 玉米农田　；参考：《中国农业大学》2017年博士论文

【摘要】：水资源短缺已成为影响地区农业经济可持续发展的严重障碍。随着节水灌溉技术和覆膜技术在干旱地区的推广,研究覆膜灌溉条件下农田土壤-植物-大气(SPAC)水分循环的机理,分析覆膜条件下土壤水分的传输和转化及作物水吸收利用过程,阐明作物水分利用效率的提升机制,对旱区水资源科学配置与调控具有重要的意义。本研究以制种玉米农田为研究对象,采用水同位素分析仪、多通道大气水汽冷阱、涡度相关系统和包裹式植物茎流计等设备。结合同位素守恒和水量平衡原理、同位素IsoSource模型、Keeling plot模型、Craig-Grodon模型以及Rayleigh蒸馏模型,对交替沟灌(AFI)、常规沟灌(CFI)、畦灌(BI)和交替沟灌1/2灌水量处理(AFI(M/2))等条件下土壤水分运动规律、玉米根系吸水模式、土壤-大气水分传输和转化机制以及农田蒸发蒸腾量的估算和区分等进行了深入系统的试验研究,取得以下成果:(1)拟合了西北旱区降水线 LMWL:δD=7.4δ18O+8.0(R2=0.95)和土壤水线 SWL:δD = 5.6δ18O-9.9(R2=0.90),明确了土壤水、植株水和大气水汽的氢氧同位素分布特征和时空变化规律。降水线截距和斜率均小于全球降水线,表明了当地较高的蒸发强度和蒸发速率。土壤水氢氧同位素在垂直方向剖面呈现明显的梯度分布,随土层深度增加而变小。玉米植株各部位同位素组成存在显著差异,叶脉与木质部水分同位素不发生分馏。作物蒸腾水汽同位素及其水汽浓度是影响农田背景水汽同位素组成的主导因素。(2)进一步揭示了交替沟灌提高作物水分利用效率和产量的机理。不同灌溉条件下玉米根系吸水模式存在显著差异,玉米主要吸水深度为:AFI(M/2)AFICFIBI。玉米全生育期内,影响其根系吸水的主导因素是根系分布,而在一个灌溉周期内,影响玉米根系吸水的主导因素是土壤水分。玉米出现干旱胁迫后,湿润根区的水分优先供应地上部分组织再进行横向运输。AFI条件下作物吸收深层和湿润侧土壤水分比例提高4-26%,减少水分渗漏损失,玉米产量相应的提高了 17.0-30.4%。当减少50%的灌溉水量时,AFI(M/2)不明显减少产量,作物的水分利用效率显著提高 13.3-33.8%。(3)建立了覆膜条件下土壤蒸发的同位素模型,定量分析了覆膜条件下农田土壤蒸发水分相变过程。覆膜条件下,土壤蒸发前缘主要发生在5-10 cm 土层,蒸发水汽分子通过土壤孔隙向上扩散,部分水汽分子被0-5 cm的土壤水吸附并与其水分子发生交换进而扩散到外界。玉米全生育期平均4.5%的膜下土壤水分发生蒸发并形成水汽,其中72.6%蒸发水汽在膜下冷凝形成凝结水,其中70.0%发生二次蒸发再次形成水汽扩散到外界,平均蒸发量约为0.80 mm/d,蒸发比例FE约为21.2%。覆膜条件下,裸土面积占的比例虽然很小(0.5-5%),但土壤蒸发比例依然较大。(4)提出了基于稳定同位素的农田蒸发蒸腾量估算和区分的新方法。实现了在同位素稳定状态(ISS)和非稳定状态(NSS)下对玉米植株蒸腾水汽的同位素组成δT直接而连续的测定。基于稳定同位素方法对农田蒸发蒸腾量的估算和区分表明,玉米蒸腾比例(FT)随季节变化较大,在生育前期较小中期较大,到后期缓慢下降。玉米全生育期内蒸腾比例范围为52-91%,平均值为78%。蒸腾比例(FT)与叶面积指数(LAI)具有良好的非线性关系:FT=0.71LAI0.14,叶面积指数LAI可以作为一项重要的指标用于衡量植被的蒸腾比例和评估作物耗水关系。
[Abstract]:Water shortage has become a serious obstacle to the sustainable development of agricultural economy in the region. With the popularization of water-saving irrigation technology and film mulching technology in arid areas, the mechanism of soil plant atmosphere (SPAC) water cycle under the condition of film mulching irrigation is studied. The transmission and transformation of soil moisture under the condition of mulching and the absorption and utilization of crop water are analyzed. The process, clarifying the mechanism of raising water use efficiency of crops, is of great significance to the scientific allocation and regulation of water resources in dry areas. In this study, a water isotope analyzer, a multi-channel atmospheric water vapor trap, a vorticity related system and a parcel plant stem flow meter were used in the study of maize cropland. Quantity balance principle, isotopic IsoSource model, Keeling plot model, Craig-Grodon model and Rayleigh distillation model, soil moisture movement law, maize root water absorption pattern, soil air water transport and transformation mechanism, under the condition of alternate furrow irrigation (AFI), conventional furrow irrigation (CFI), border irrigation (BI) and alternate furrow irrigation 1/2 irrigation (AFI (M/2)). The results are as follows: (1) fitting the precipitation line LMWL: Delta D=7.4 Delta 18O+8.0 (R2=0.95) and soil waterline SWL: Delta D = 5.6 Delta 18O-9.9 (R2=0.90) in northwest dry area, and the distribution characteristics of hydrogen and oxygen isotopes of soil water, plant water and atmospheric water vapor, and the time and space of time and space are clearly defined. The intercept and slope of the precipitation line are smaller than the global precipitation line, which shows the high local evaporation intensity and evaporation rate. The soil water hydrogen and oxygen isotopes show a distinct gradient distribution in the vertical direction and smaller with the increase of soil depth. There are significant differences in the isotopic composition of different parts of the maize plants and the moisture of the leaf vein and xylem. Isotopes of isotopes are not fractionated. Crop evapotranspiration and water vapor isotopes and water vapor concentration are the dominant factors affecting the composition of water vapor isotopes in farmland. (2) the mechanism of increasing crop water use efficiency and yield by alternate furrow irrigation is further revealed. There is significant difference in the water absorption pattern of maize root system under different irrigation conditions and the main water absorption depth of Maize In the whole period of AFI (M/2) AFICFIBI., the dominant factor that affects its root water absorption is the distribution of root system. In a period of irrigation, the dominant factor affecting the water absorption of maize roots is soil moisture. After the drought stress of maize, the water in the moist root region is given priority to the part of the soil and then transversely transport the crops under the condition of.AFI. The ratio of soil moisture absorption in deep and humid sides increased by 4-26%, reducing the loss of water leakage. The corresponding increase of maize yield by 17.0-30.4%. when 50% of the irrigation water was reduced, AFI (M/2) did not decrease the yield obviously, and the water use efficiency of the crop was significantly increased by 13.3-33.8%. (3), the isotopic model of soil evaporation under the condition of mulching was built, and the quantitative analysis was established. The process of evaporation and moisture transformation in farmland soil under the condition of film mulching was analyzed. Under the condition of film mulching, the evaporation front of the soil mainly occurred in the 5-10 cm soil layer. The evaporation water vapor molecules spread upward through the soil pore. Some of the water vapor molecules were adsorbed by 0-5 cm soil water and exchanged with the water molecules to spread to the outside world. The average growth period of maize was 4.5%. The soil moisture under the membrane evaporates and forms water vapor. 72.6% of the evaporation water vapor condenses under the film to form condensate, and 70% of them evaporates two times to form water vapor to spread to the outside world, and the average evaporation is about 0.80 mm/d, and the proportion of evaporation is about FE under the condition of 21.2%. covering, although the proportion of bare soil area is very small (0.5-5%), but soil evaporation The proportion is still large. (4) a new method of estimating and distinguishing the evapotranspiration of farmland based on stable isotopes is proposed. The direct and continuous determination of isotope composition of transpiration of maize plants under the isotopic state (ISS) and the unstable state (NSS) is realized. The estimation of the evapotranspiration based on stable isotope method is used to estimate the evapotranspiration of farmland The calculation and distinction showed that the transpiration ratio (FT) of maize was larger with the season, and it was larger in the small and medium period of the early growth period and slowly declined in the later period. The transpiration ratio of Maize in the whole growth period was 52-91%, and the average value of 78%. transpiration ratio (FT) and leaf area index (LAI) had a good nonlinear relationship: FT=0.71LAI0.14, the leaf area index LAI could be used as a LAI. An important indicator is used to measure the transpiration ratio of vegetation and to assess the relationship between crop consumption and water consumption.
【学位授予单位】：中国农业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：S513

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