ИСТИНА

The work was supported by the Russian Foundation for Basic Research, grant N 15-04-04702. Modern urban environments are characterized by the active relocation of ground masses with the formation of new layers of technogenic deposits. The surfaces undergo continuous changes caused by intensive land use and the development of newly built-up areas. As a result, city soils, as a rule, are quite young. The complex of buildings of the main campus of the Lomonosov Moscow State University (LMSU) on the Leninskie Hills at the south-west of the city was constructed in the middle of the 20th entury. Following the completion of the buildings, a botanical garden was established together with general land ameliorations within the LMSU campus. Prior to the campus construction, the whole area of Vorob’evy Hills was occupied by rural settlements, fields and woodland patches. The soils studied were formed on similar technogenic deposits – ‘building grounds’, from 0.3 to 3 m thick, composed of mixed silty-loamy materials with fragments of horizons of native soils (Albic Retisols) and inclusions of building waste. Calcareous inclusions were very rare or absent within the surface layer, where the modern pedogenesis takes place. The pedogenesis on these deposits began over 60 years ago, at the time of general land ameliorations following the construction of the LMSU campus. Currently, the campus includes a harmonious ombination of buildings, roads of various sizes, lawns, planted trees and the botanical garden comprising dendrarium, orchard, plots of cultivated plants, etc. Studied soil pits were located in the botanical garden, on road-side lawns and under planted trees. The land management within the botanical garden involved the complete removal of fallen leaves in autumn from all parts of the garden, except the dendrarium. However, since 2011, only a partial removal of leaves has been practiced. The lawns have been regularly improved by additions of fertile composts. The botanical garden soils had a magnetic susceptibility of 0.5-0.1 SI, which is a double or triple of that in background soils. The road-side lawn soils had a magnetic susceptibility of 1-3 SI, which is comparable to mean values over the city. The rate of accumulation of airborne solid deposits varied from 100 to 400 kg/km2 per day in the soils studied, which corresponds to low and medium accumulation rates within Moscow that are themselves 10-40 times higher than those outside the city (Prokofieva et al., 2017). Most soils of the study site can be classified as Technosols and Anthrosols, according to the WRB. They can be subdivided into two groups depending on general pedogenetic trends. The first group includes soils having typical postlithogenic pedogenesis and the А-АС-С profile, located within areas of low anthropogenic pressure. The second group connected with the synlithogenic trend of pedogenesis comprises a greater diversity of soils: some of them have an incrementally growing humus horizon due to compost additions, while others have a specific urban humus horizon (urbic) and have been termed by us as Urbostratozems (Prokof ’eva et al., 2014). Urbostratozems are formed within areas, where a significant rate of airborne dust deposition is combined with occasional deposition of solid waste and possible additions of fertile composts. The urbic horizons that developed over a period of 60 years were relatively thick, with a distinct tendency for horizontal splitting of structural units, high contents of artefacts of all sizes and well-developed processes of chemical properties transformation. There were also some buried soils, both natural and agriculturally transformed, preserved under shallow technogenic deposits within the botanical garden. All studied soils were characterized by eutrophication of their surface horizons due to depositions of airborne alkali salts and ice-melting agents leaking from roads. Soils with neutral to alkaline reaction developed on initially non-calcareous and weakly-calcareous parent rocks. Their surface horizons contained up to 3% of carbonates. The high content of phosphorus compounds in non-fertilized soils outside the botanical garden could have originated from the excreta of domestic animals and city birds. Soil pollution by microelements was at low to medium levels. Judging by the particle-size distribution, the natural and technogenic parent rocks were silty loams. The urbic horizons of soils subjected to higher anthropogenic pressure near roads were sandy loams. According to bulk density measurements, soil compaction was insignificant. A general trend of the current formation of highly humified horizons was revealed. The absence of the removal of fallen leaves within the dendrarium of the botanical garden resulted in the formation of horizons with humus content up to 9-11%. There was a lesser degree of organic matter accumulation under conditions of soil improvement through compost additions. The organic matter in the soils studied has different characteristics from that in native soils of the southern taiga belt, i.e., it has features typical for more southern pedogenesis. However, a general ‘forest-type’ character of humus is preserved (Rozanova et al., 2015). Macromorphologically, the results of 60-year-long pedogenesis were expressed in the formation of humus horizons. Micromorphologically, soil-forming processes were dentified as follows: structuring of technogenic grounds due to their processing by soil fauna; vertical migration of humus and clay in the absence of carbonates; mineral weathering and decomposition of inclusions within soil; and the formation of calcareous and ferruginous pedofeatures. The processes of iron redistribution and disperse humus accumulation have led to the formation of films on the surfaces of calcareous nodules, which apparently improved the stability of such nodules under conditions of a percolative water regime. Thus, general trends of soil development within the LMSU campus, where pedogenesis has not been interrupted by new additions of technogenic grounds for a period of 60 years, are determined by a combination of non-catastrophic anthropogenic impacts. Namely, there are depositions of inorganic materials onto the soil surface (airborne dust deposition, waste accumulation and compost addition) and accumulations of organic matter varying in volume and composition (removal or non-removal of fallen leaves, addition of organic-rich composts and pollution by carbohydrates). The subdivision of pedogenesis into two main directions, postlithogenic and synlithogenic, depends on the rate of mineral matter accumulation on soil surface and applies to the road-side locations and the areas, where soils have been improved by regular compost additions.