Variation in the properties of chernozems in the Priob Plateau within the boundaries of the key site “Volodarka” (Altai Territory, Russia)

Abstract

The aim of the study. To assess spatial heterogeneity of the chemical properties of the chernozems of the Near-Ob Plateau within the boundaries of the key site “Volodarka” and explain the reasons that determined the variation of the studied soil properties. Location and time of the study. Steppe zone of the northeastern part of the Near-Ob Plateau within the boundaries of the key site “Volodarka” (52°41-42' N and 83°38'E); the results of the long-term research (2007–2019) are discussed. Objects of the study. Chernozems that formed under the dry-steppe vegetation on loess deposits, as well as on different horizons of paleosols of Middle Pleistocene origin that reached surface. Methodology. Soil samples were collected to a depth of 40 cm in a continuous column at an increment of 2 to 10 cm, taking into account the visible boundaries of genetic horizons. To characterize soil chemical properties, the methods commonly used in Russian soil science studies were used. Specifically, soil organic carbon content was determined by dichromate digestion method. Results. The studied properties of chernozems, currently functioning in the same environmental conditions of the key area located on the territory of the Altai Territory, showed significant variation, as can be judged by comparing their means and coefficients of variation. The greatest fluctuations in all soil properties in all soil profiles were observed, as a rule, in the 10–20 or 20–40 cm layers, whereas in the 0–10 cm layer they changed less significantly. It was revealed that the degree of humification and humus reserves, as well as nitrogen reserves and the nitrogen enrichment of humic substances in the 0-40 cm layer, can be regarded as significant; they displayed the greatest variation in the 20–40 cm layer. Conclusions. The heterogeneity of the main properties of chernozems located in the same natural conditions of the Priob Plateau within the boundaries of the key site “Volodarka”, even within 0-40 cm layer, is most likely due to the currently present features of ancient pedogenesis. Those features do not correspond to the combination of modern soil formation conditions of the dry-steppe type: it is confirmed by the presence and extent of clearly visible Middle Pleistocene pedocomplexes in the coastal outcrops of the Ob River. Different horizons of those pedocomplexes reached the surface and had been overlayed by products of modern soil formation in layers of different thicknesses. The combination of heterogeneity of soil profiles in terms of properties, position in the coastal outcrop and their visual differentiation allowed us to conclude that the variation in the compositional characteristics and properties of the studied soils resulted from the history of the territory development, which determined the surfacing of the buried paleosols. The knowledge of the heterogeneity of soil profiles makes it possible to use the studied soil properties and characteristics of their composition for monitoring the state of modern soils, substantiating forecasts of their behavior under changing ecological conditions, as well as for identifying features of ancient pedogenesis in order to reconstruct the paleonatural environment.