Micromorphology of diagnostic horizons in aridic soils (complementary to the new classification system of soils of Russia)

The micromorphological data on aridic soils are far from numerous; therefore, the information presented here contributes to the development of pedogenetic ideas and characterization of diagnostic horizons and genetic properties in substantive-genetic classification systems. The diversity, functioning, and resilience of aridic soils are basically determined by the properties of their topsoils, which are regarded as recent dynamic formations as opposed to subsoils that formed under a different paleoclimatic environment; topsoil properties are more important for soil classification. Each of the two upper horizons in the new system of soil classification (the light-humus and xero-humus) has the same micromorphological features in different soils; however, in a sequence of soils, some individual micromorphological properties were revealed that indicate increasing aridity. The micromorphological properties of topsoils make it possible to identify the mechanisms of certain phenomena: aeolian deposition, structural rearrangement, the dynamics of secondary carbonates, and cryptosolonetzic manifestations.