灰色关联及非线性规划法构建传递函数估算黑土水力参数

    Constructing pedo-transfer functions based on grey relational and nonlinear programming to estimate hydraulic parameters in black soil

    • 摘要: 土壤水分特征曲线和饱和导水率是重要的水力参数,为了简便准确获取这些参数,以松嫩平原黑土区南部为研究区域,采集136个采样点土样用于测定不同土层土壤水分特征曲线、饱和导水率以及土壤理化性质,并运用灰色关联分析确定影响土壤水力参数的主要土壤理化性质,采用非线性规划构建土壤分形维数、有机质、干容重、土壤颗粒组成与土壤水分特征曲线、饱和导水率之间的土壤传递函数,并通过与现有土壤传递函数对比分析进行精度验证。结果表明:1)土壤分形维数是估算土壤水分特征曲线模型参数和饱和导水率的主要参数之一,同时,干容重和有机质含量也在不同土层土壤传递函数中起到重要的作用;2)通过验证分析,不同土层各参数平均绝对误差接近于0,均方根误差值也都较小,其中在不同土层土壤传递函数估算的土壤含水率均方根误差分别为0.022、0.017 cm3/cm3;3)对比分析其他已存的土壤水分特征曲线和饱和导水率的土壤传递函数,该文构建的土壤传递函数均方根误差值均较小,决定系数值都在0.66以上,表明估算精度较高,均好于其他方法估算精度,具有良好的区域适应性。综上,所构建的土壤水分特征曲线和饱和导水率土壤传递函数可以用于松嫩平原黑土区土壤水力参数估算。

       

      Abstract: Abstract: Soil water characteristic curve and saturated hydraulic conductivity are important parameters for constructing soil moisture and solute transport models, both of which are affected by soil texture, bulk density, organic matter content, porosity, etc. In order to simply and accurately obtain the 2 parameters above, a total of 136 soil sampling points in the southern part of the black soil area in the Songnen Plain were designed, and the soil samples in 2 layers of these sampling points were collected to measure the soil water characteristic curve, saturated hydraulic conductivity and soil physical and chemical properties, the grey correlation analysis was used to determine the main soil physical and chemical properties affecting soil hydraulic parameters.The results showed: 1) in 0-20 cm soil layer, the residual moisture content of van Genuchten model had the higher correlation with fractal dimension, dry bulk density and organic matter content, and the correlation between parameter pore distribution index and fractal dimension, dry bulk density and clay content was the highest. The parameter of reciprocal soil air influx had the higher correlation with sand content, dry bulk density and fractal dimension. In soil layer from 20 to 40 cm, the parameter of residual moisture content of van Genuchten model had the higher correlation with sand content, dry bulk density and organic matter content; the parameter pore distribution index and fractal dimensions had the highest correlation; The correlation between fractal dimension, organic matter content and silt content and parameter pore distribution index was the highest, and the correlation between parameter reciprocal soil air influx and sand content, fractal dimension and organic matter content was the highest. 2) The correlation between soil saturated hydraulic conductivity and soil organic matter, dry bulk density and fractal dimension in 0-40 cm soil layer was higher. 3) The pedo-transfer functions of the soil water characteristic curve and the saturated hydraulic conductivity based on soil fractal dimension, organic matter, dry bulk density and soil particle composition were established by using the nonlinear optimal programming method. The accuracy of the pedo-transfer functions established in the study was verified by comparing with the existing common pedo-transfer functions. The results showed that soil fractal dimension was one of the primary parameters in constructing soil pedo-transfer functions to predict soil water characteristic curve and saturated hydraulic conductivity. In addition, soil dry bulk density and organic matter content also played an important role in pedo-transfer functions of different soil layers. Based on the verification analysis, the mean absolute errors of the estimated soil hydraulic parameters in different soil layers were all close to 0, and the root mean square error values of the predicted soil hydraulic parameters in different soil layers were also small. Specially, the root mean square errors of soil moisture content estimated by pedo-transfer functions established in the study were 0.022 and 0.017 cm3/cm3 in different soil layers, respectively. On the basis of comparing with the other existing common pedo-transfer functions of soil water characteristic curve and saturated hydraulic conductivity, the pedo-transfer functions of soil hydraulic parameters established in the study had high estimation accuracy, the root mean square error values were small; the determination coefficient values were all above 0.66, which was better than the other existing common pedo-transfer functions. In summary, the pedo-transfer functions of the soil water characteristic curve and saturated water conductivity established in the study can be used to estimate the soil hydraulic parameters in the black soil area of the Songnen Plain, and also provide technical support for acquisition of regional soil hydraulic properties.

       

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