Diagnostics of lithic discontinuity of soils based on fractal properties of coarse/fine-related distribution

Abstract

In the study of soil genesis and the determination of their systematic position, the diagnosis of the lithological heterogeneity of the parent rock is important. In the World Reference Base of Soil Resources (IUSS Working Group WRB 2015) lithological heterogeneity is defined as significant changes in the particle size or mineralogical composition, which reflect the lithological differences within the soil profile and a number of diagnostic criteria for lithological heterogeneity are given. At the level of soil microstructure, these are the characteristics of the relative distribution of coarse and fine particles of the solid phase (c/f relative distribution). Using the example of forest soils formed on colluvial sediments, we consider the possibility of using the fractal properties of the c/f relative distribution to diagnose the lithological heterogeneity of the genetic profile of the soil and establish the contrast of such heterogeneity. A micromorphological study of the soils formed on the parent rocks of loamy and clay granulometric composition reveals the fractal structure of the relative distribution of coarse and fine particles, which is the quantitative and qualitative characteristic of the solid phase and is not recognized by the particle size analysis. In the study with different magnifications, the multilevel structure of the c/f of the relative distribution is manifested in the possibility of selecting not one, but several c/f thresholds with corresponding characteristics for each. It is important that the overall picture of the microstructure at each level of the c/f of the relative distribution is similar to the picture at other levels. The algorithm for studying the fractal properties of the relative distribution is made up of successive stages: revealing the presence of the fractal structure of the c/f relative distribution; determination of similarity levels; determination of the morphometric parameters of the relative distribution at each of the revealed levels of similarity, which include the c/f threshold, the dimension of the coarse fraction, c/f ratio. An additional parameter is the spatial distribution of coarse particles at each level. The studied forest soils of the Prysamaria are characterized by a three-level fractal structure of the organization of the relative distribution of the granulometric elements of the microstructure. At each of the levels of relative distribution, the pattern of microstructure is similar to the levels highlighted in other scales. It was revealed that the profile of Luvic Chernic Phaeozem on the slope of the beam is lithologically inhomogeneous. Subsoil horizons outside the genetic profile of the soil differ in morphometric parameters at the second and third levels of the relative distribution of coarse and fine particles.