Spatial variability of soil properties

通过最小化实测值和缩尺值之间的平方和，建立了确定基质吸力、非饱和导水率和土壤水分扩散率的标度系数的方法。标度系数的确定采用了两种方法：实验方程中的估计值作为有效饱和度的函数和测量值的平均值作为标度折减值。结果表明，前者非常有用，因为只需改变约化变量中系数的值，就可以很容易地对不同的属性进行缩放。建立克里格法是为了从有限的测量值中估计未知值。首先确定一个半方差函数作为滞后距离的线性方程。然后，通过最小化估计误差来确定最优邻域大小。绘制了沙丘沙地和围海造陆土壤的颗粒级配、土壤溶液离子浓度、土壤盐度和溶液pH等值线图。

A technique for determining the scaling coefficients for matric suction, unsaturated hydraulic conductivity and soil water diffusivity was established by minimizing a sum of squares between the measured values and the scale reduced values. Two methods were used in determining the scaling coefficients; the estimates from an experimental equation as the function of the effective saturation and the average of the measured values were used as the scale reduced values. Scaling effect was noticeable for any case and the similar values of scaling coefficients were obtained for the two methods. The sum of squares was smaller in the case that the experimental equation was not used than that the equation was used. It was concluded that the former was very useful because scaling is easily done-for the different properties only by changing the value of coefficients in the reduced variables.The kriging technique was established in order to estimate the unknown values from the limited number of measured values. The procedure includes the following three steps. First, a semi-variogram is determined as the linear equation of the lag distance. Next, the optimum neighborhood size is determined by minimizing the estimate error. Finally, the value at the arbitrary point is estimated from the measured values within the optimum neighborhood size. The contour maps were made for particle size fraction, ion concentration in the soil solution, soil salinity and solution pH in dune sand and reclaimed land from sea. The contour maps drawn by kriging estimates were far clearer than those drawn only by the measured values. The values of one properry could be estimated from those of another property by using the linear predictive equation between two properties with the similar distribution.