| Abstrakt: |
The features of anthropogenic transformation of natural chestnut soils and genesis of urban soils under the conditions of the dry-steppe natural zone on the territory of Volgograd have been comprehensively studied. We have compared morphological characteristics of natural soils and their anthropogenic-modified counterparts. The morphology of each of 16 transects has been described. The morphological parameters of urban and chestnut soils of the city outskirts have been compared. Natural AJ light-humus horizons disappear, and the mean thickness of diagnostic BMK xerometamorphic horizons decreases under the effect of urban pedogenesis. The upper boundary of the BCA carbonate-accumulative horizon has become deeper by 32 cm as compared to natural chestnut soils. Urban techno-pedogenesis has resulted in the appearance of inclusions represented by debris of building materials and garbage accumulated during the functioning of human settlements and in the change in soil structure, density, and effervescence. Modern surface horizons often effervesce with 10% HCl. Carbonates have been leached due to irrigation of landscaped recreational areas of the city. Four variants of morphological transformation of chestnut soils in Volgograd as a result of urban pedogenesis have been revealed: (i) soils of initial technotransformation stages with changes in the upper horizons; (ii) soils with thick urban horizons, overlapping the preserved diagnostic horizons; (iii) buried natural rocks by man-made soils of various thickness with almost complete destruction (removal) of natural soil horizons; and (iv) soils with thick humus horizons formed as a result of intensive organic matter input with compost. It is revealed that most of the soil profiles in the city are completely formed on man-made deposits and do not contain natural soil horizons to a depth of 1.5 m. According to the Field Guide for Russian Soils, the studied soils of the first transformation variant are defined as urban-stratified ones. The soils of the variants may be assigned to man-made surface formations. The content of organic carbon in the urban, technogenic, and replanted horizons averages 1.1, 0.25, and 1.6%, respectively. Chemical analysis of urbic, reclamation, and technogenic horizons has revealed a low content of easily soluble salts (0.14%) and carbonates (0.9%). Soil density averages 1.4–1.43 g/cm3 in the UR and RAT horizons and 1.55 g/cm3 in the TCH horizons. The mean density of buried soil is 1.43 g/cm3 in the AJ, 1.49 g/cm3 in the BMK, 1.62 g/cm3 in the B, and 1.54 g/cm3 in the BCA horizons, which is higher than the mean density of native chestnut soils. The buried horizons are also characterized by leaching from salts, a lower content of calcium carbonate than in the background soils, alkalization of medium, as well as a decrease in organic carbon by 0.35% on average in the AJ, BMK, and B horizons and by 0.28% in the BCA horizon. The mean CaCO3 content is 1.4% in the upper humus and middle horizons and 4.3% in the carbonate horizon. The data obtained enable a more comprehensive study of specific features of genesis of urban soils and of the anthropogenic transformation of natural chestnut soils under urban conditions of the dry-steppe natural zone. [ABSTRACT FROM AUTHOR] |
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