【作者】 李彩霞；

【导师】 孙景生；

【作者基本信息】 中国农业科学院 ， 农业水土工程， 2011， 博士

【摘要】 沟灌SPAC系统水热传输的数值模拟,对摸清SPAC中水热能量输送与转换的定量关系,揭示隔沟交替灌溉的节水机理及水热能量传输特性等具有重要的理论意义和生产实际意义。本研究在前期研究现状的基础上,以大田玉米为试验材料,采用隔沟交替灌溉(AFI)和常规沟灌(CFI)两种沟灌方式,通过对地面光温分布、土壤水热参数、根系分布、作物生理指标等试验测定,分析了作物生长期间的地面光温分布规律以及土壤表面阻力、冠层阻力、空气动力学阻力与环境因素的关系,建立了各阻力模型,进一步构建了地面光温分布模型、土壤蒸发二维模型、根系吸水二维模型和土壤水热传输模型,揭示了AFI与CFI条件下土壤蒸发机制、根系形态对土壤水分的响应机制和水热传输特性,从整体上与相互反馈关系上建立了SPAC水热传输二维动态模型,实现了SPAC系统水热变化的动态模拟。研究取得的主要结果和结论如下:(1)东西行向播种时地面太阳总辐射量高于南北行向。同一播种行向时,AFI在非灌水区域地面所接受的太阳总辐射量高于灌水区域,因此AFI地面所接受的太阳总辐射量高于CFI。地表温度变化曲线同太阳辐射变化趋势非常一致,东西行向播种时地表温度高于南北行向。同一行向播种时,AFI的地面温度高于CFI,最大温差为4.23℃,最小温差为0.06℃。根据地面结构与太阳入射角度的几何关系建立地面太阳总辐射传输和地表温度分布模型,较好地模拟了沟灌田间太阳辐射和地面温度变化,拟合度在0.84以上。(2)改进了S-W模型,将AFI条件下土壤蒸发分为灌水区域和非灌水区域两部分,建立了沟灌条件下土壤蒸发二维模型和作物蒸腾模型。在Camillo(1986)和Anadranistakis et al(2000)模型基础上,建立了适于AFI灌水与非灌水区域的土壤表面阻力模式。提出了非充分供水条件下由冠层内温差表示的气孔阻力响应函数,在Jarvis(1976)模型基础上,建立了充分供水和非充分供水条件下的冠层阻力模型,模型待定系数经最小二乘法反复迭代,确定最优解。土壤蒸发模0实拟.3测值3值与和的实0.测807.8值;8有C倍F很,I的好C F的MI一A的E致作、性物?,蒸??A腾?F I和量的?模??土?分拟壤别结蒸为果发为0模.0实拟9、测值0值与.3的1实和测0. 80值5.9间倍0。的。A MFAI的E、作??物??蒸和腾??量??分模别拟为结0果.1为1、(3)AFI条件下,根系直径、体积密度、根尖数和表面积对土壤水热环境形成了自身的响应机制,受旱根区复水后根系生长速率加快,死亡速率变缓,根系形态出现“补偿效应”。AFI的细根根尖数和表面积较CFI增大,根系下扎更深,有利于根系吸水。根长密度在侧向和垂向土层深度上均呈指数递减分布。在玉米抽雄期之前,AFI的根长密度在垄位两侧不对称分布,受降雨影响,在玉米抽雄期之后,根长密度逐渐呈对称分布。CFI的根长密度在垄位两侧呈对称分布。建立了根长密度二维分布模型,AFI和CFI的根长密度模拟结果与实测值比较一致,二者的相关性决定系数在0.80以上。根据根长密度的动态分布和Feddes et al(1978)模型,建立了水分胁迫条件下的根系吸水二维动态模型。(4)有限元法对模拟区域的划分减小了复杂边界和非均质土壤引起的误差,有限元法的Galerkin方程提高了模拟精度,较好地模拟了AFI与CFI条件下土壤水热在时间上和空间上的传输过程,模拟结果与实测值有很好的相关性,土壤水分运动模拟值为实测值的0.96倍;而土壤温度的模拟值与实测值基本吻合,模拟值为实测值的0.98倍。本研究的主要创新点:①根据光学几何原理,考虑地面处于遮阴区和日晒区以及土壤湿润方式,建立的沟灌地面太阳总辐射传输模型和地表温度分布模型,较好地模拟了地面不同点位处光温分布规律。②确定了适合新乡轻砂壤土在AFI和CFI条件下的土壤表面阻力计算方法。所建立的冠层阻力模型中,水分亏缺条件下的气孔阻力响应函数由冠层温度表示,数据获取方便、快捷,优于土壤水分表示法,而且能够计算冠层阻力的日变化值,实用性强。③考虑沟灌地表复杂边界条件、土壤水分的非均匀性和地面小气候变化,改进了S-W模型,建立了沟灌条件下的二维土壤蒸发模型和作物蒸腾模型,蒸发蒸腾量的模拟值与实测值间的MAE、RMSE小于1,di在0.87以上。④揭示了活根/死根根系形态对沟灌土壤水分环境的响应机制。所建的根长密度分布模型,考虑了根系的空间分布以及根系伸展、下扎长度随时间变化,模拟精度较高,具有动态性。更多还原

【Abstract】 It was very important to model water and heat transfer in SPAC under furrow irrigation for understanding the quantitative relationships between energy transmission and transition of SPAC, and elucidating the water-saving mechanism and characters of energy transmission of alternative furrow irrigation (AFI). Based on the current situation of water and heat transfer simulation of SPAC under furrow irrigation, the light and temperature distribution on soil surface and the relationships between soil surface resistance, canopy resistance, aerodynamic resistance and environmental factors were analyzed with observations of the light and temperature distribution, soil water and heat transfer parameters, crop root distribution and crop physical indices of maize under AFI and convention furrow irrigation (CFI), and various resistance models were also developed; furthermore, the model of light and temperature distribution on soil surface, two-dimensional model of soil evaporation and root water uptake, and soil water and heat transfer model was developed; the mechanism of soil evaporation, the response mechanism of root morphology to soil moisture and the characters of soil water and heat transfer under AFI and CFI was revealed; the 2-D water and heat transfer model of SPAC under furrow irrigation was developed with the mutual feedback relationships, achieving the dynamic simulation of water and heat variation of SPAC under furrow irrigation. Results were as follows:(1) Total amount of solar radiation on soil surface with West-East row was greater than that with North-South row. For spring maize under AFI with the identical row orientation, solar radiation quantities on non-irrigated zone was greater than that on irrigated zone, therefore, solar radiation quantities on soil surface under AFI was greater than that under CFI. Soil surface temperature variation curve was similar to solar radiation variation trend. Soil surface temperature with West-East row was greater than that with North-South row. For maize with the identical row orientation, soil surface temperature of AFI was greater than that of CFI, the maximum temperature difference and the minimum difference was 4.23℃and 0.06℃, respectively.The model of global radiation transfer on soil surface and soil temperature distribution was developed based on the geometrical relationships between soil surface structures and the incident angle of solar radiation. Variations of solar radiation and soil surface temperature under furrow irrigation were well simulated with the model, and the fitting degree was greater than 0.84.(2) The 2-D model of soil evaporation and crop transpiration under furrow irrigation was developed with the improved S-W model based on dividing soil evaporation zone to wet and non-wet zones under AFI. Soil surface resistance model of dry and wet region under AFI was developed with the Camillo (1986), and Anadranistakis et al (2000) model. The response function of stomatal resistance to water stress under deficient water supply was expressed as the temperature difference in the interior of canopy. Based on the Jarvis (1976) model, canopy resistance model was developed under adequate and deficit water supply; the undermined parameters of the model were calculated with the least square method, then the optimal solution was determined. The simulated values of soil evaporation were similar to the measured values. The relative deviation (MAE), root-mean-square deviation (RMSE) and fitting degree (dl) between the simulated and measured values under AFI was 0.11, 0.33 and 0.87, respectively; the values of MAE, RMSE and dl under CFI were 0.09, 0.31 and 0.90, respectively. Crop transpiration was underestimated with the model. The simulated transpiration under AFI was 0.88 times of the measured values, and the simulated values under CFI were 0.85 times of the measured values.(3) Under AFI, root diameter, root volume density, root tip number, and surface area present the response mechanism to soil water and heat environment. Root growth rate of root zone with water deficit was increased significantly after re-watering, the root death rate decreased, and the‘compensational effects’present. Values of root tip number and surface area of fine root under AFI was significantly greater than that under CFI; root depth under AFI was greater than that under CFI, which was favorable to root water uptake.Root length density (RLD) decreased exponentially with depth in lateral and vertical profile. RLD of AFI was not symmetrical distributed with ridge before jointing; RLD was symmetrical distributed with ridge after tasseling. RLD under CFI was symmetrical distributed with ridge. The two-dimensional distribution model of RLD was developed, the simulated values of RLD at different sites under AFI and CFI were similar to the measured values, coefficient of determination were higher than 0.80. The 2-D model of root water uptake under water stress condition was developed with the dynamic distribution of RLD and the Feddes model (Feddes et al., 1978).(4) The simulation errors caused by complex boundary and homogeneous soil were decreased with the division of the simulated domain using the finite element method, and the simulation precision increased using the Galerkin method. Soil water and heat transfer in time and space under AFI and CFI was nicely simulated using the finite element method; the simulated values had a significant correlation with measured values, the simulated values were 0.96 times of the measured values. The simulated values of soil temperature were similar to the measured values, the simulated values were 0.98 times of the measured values.Main innovative points of this paper:①The model of global radiation transfer on soil surface and soil temperature distribution was developed based on the geometric optics, and taking into account of overshadow zone and sunshine zone and soil moist pattern. The light and temperature distribution on different sites of soil surface was well simulated with the model.②The calculation method of surface resistance under AFI and CFI for sandy loam soil at Xinxiang was determined. For the developed model of canopy resistance, the response function of stomatal resistance to water stress under deficient water supply was expressed as the temperature difference in the interior of canopy, which could be easily and simply measured, being superior to express as soil moisture; values of daily variation of canopy resistance could be calculated with themethod, which was feasible and practical.③The S-W model was improved with the complex boundary conditions of furrow irrigation, the homogeneity of soil moisture and variation of microclimate on soil surface, then the 2-D model of soil evaporation and crop transpiration under furrow irrigation was developed, and the values of MAE, RMSE between the simulated and measured values was less than 1, and di greater than 0.87.④The response mechanism of the live and dead roots morphology to soil water condition under furrow irrigation was analyzed, and the 2-D model of root length density distribution, which taking account of the space distribution of root system, and variation of depth of root spread and penetration with time, has high simulation precision and dynamic characters.更多还原