Megacities 2050: Environmental Consequences of Urbanization by Viacheslav I. Vasenev Elvira Dovletyarova Zhongqi Chen & Riccardo Valentini

Author:Viacheslav I. Vasenev, Elvira Dovletyarova, Zhongqi Chen & Riccardo Valentini
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

4 Discussion

4.1 Humus State of Urban Soils

The most of Calcic Chernozem profiles with a high content of organic matter in the surface horizon is confined to the so-called forest park “protective” belt has framing the city of Rostov-on-Don from its eastern and north-eastern sides. This is due to the fact that under the tree vegetation the way in which the plant residues enter the soil is different from the same process in steppe; as a consequence, there is a change in the distribution of humus along the profile. The presence of litter that is produced in forest from fallen leaves and a thick grass cover, protected from the summer fading by the crowns of the trees, is a source of energetic material, enriching the soil with humus and other mineral and organic compounds. As a consequence, humus profile acquires the features of the forest soil: a quite dramatic humus decrease with depth compared to the upper horizons can be noted. Such pattern of humus distribution is characteristic of the nearest northern “neighbor” of Chernozems – dark gray forest soils (Phaeozems). Ponomareva and Plotnikova [27] called a similar distribution of humus in the soil profile “forest type of accumulation of organic matter”.

Such an increase in the concentration of organic matter in soils of Moscow was mentioned in the works of Prokofieva and others [31], confirming the fact that similar processes are not unique to urban soil of southern Russia.

Thus, the forest-park “protective” plantings at the outskirts of the city ensuring the creation of wind barrier, and thus the favorable climate of the city are also a dynamic environment-forming factor, leading to the formation of “islands” of a totally different type of matter redistribution in the plant-soil system on a background of steppe nutrient cycle. The tree plantations in steppe are the centers of more intense cycle of matter than the natural steppe communities, and even more intense when compared to arable land.

At the same time, on the fallow plots compared to the cropland some increase in humus content of the upper soil horizons has been noted. When plowing destroys the natural vegetation, the annual flow of all biomass created during the vegetation period stops, and there is a change of redox regime. As a result of this the organic matter changes qualitatively.

Regarding anthropogenically transformed soils, the processes of burial and sealing practically cease the flow of the fresh organic matter to the soil, contemporary processes of humification are damped and, as a consequence, there is no update of humic substances [10]. As a consequence, there is a significant change in the carbon and nitrogen cycles dynamics in the buried soil stratum [17, 26]. In addition, a large proportion of contaminated sediments bypasses soil body, and all this leads to the fact that the possibilities for the soil and humus to conduct their protective features are sharply reduced. Such sealed soils can be regarded as anthropogenic models, reflecting the effect of time on the functioning and the status of soil humic substances system.

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