Assessing soil fractal and sorting characteristics based on geostatistics and modeling approaches in a typical basin of North China plain

Fractal dimension is a parameter that quantitatively describes the complexity of fractal set. In order to understand the spatial variation characteristics of soil fractal dimension and its influencing factors, different geomorphic units in a typical basin of the North China plain were selected for sampling. And the grain size distribution of 180 soil samples were measured by laser diffraction. Fractal dimension was analyzed by the software of SPSS26 and Voxler4.3 to search for significant influencing factors. Then, in the same coordinate system as fractal dimension, models of soil particle sorting were built. There was a decreasing trend from the sloping plain at the southwest piedmont (1.6244) towards the alluvial plain (1.2164) about fractal dimension. In piedmont plain, fractal dimension was significantly correlated with the minimum particle size and proportion of clayey particles, respectively. In coastal plain, fractal dimension was extremely significantly correlated with the maximum particle size and the proportion of sandy particles, respectively. The spatial variability of soil structures in the study area was significant. The models features of sorting and fractal dimension are similar, and a linear relationship existed between fractal dimension and standard deviation as follows: D = 1.236σ₁ + 0.082. This research supports quantitative and visual characterization of spatial variability of soil structure and sorting of soil particles.