Analysis of Volume and Properties of Imported Soils for Prediction of Carbon Stocks in Soil Constructions in the Moscow Metropolis

Development of landscaping in modern cities makes it particularly important to study the properties and functions of artificial soil constructions. Carbon sequestration is one of the main ecological functions of soils, which is actively studied for the soils of natural and agroecosystems but is poorly known for urban and technogenic soils. Anthropogenic impacts are a key factor that influences the formation of carbon stocks in urban soils and, in particular, in soil constructions, characteristic of which is a high and hardly predictable heterogeneity. One of the main factors that determines the carbon pools in the soil constructions of Moscow metropolis is the volume and properties of imported soils. We have analyzed the market of soils supplied to Moscow for landscaping purposes in 2016 and 2017, the sources and volumes of imported soils and their components, their recipes, and properties using the surveys of supplier companies. Based on these data, the predicted average organic carbon stock in the upper (0–10 cm) soil layer is 84 t/ha. A comparison of our estimates and field survey data for a representative sample of Moscow soil monitoring points (n > 190) shows that the prediction gives a 1.5–2.0-fold overestimation. However, a relatively small absolute excess (by 30–40 t/ha) and similar yearly dynamics of the predicted and actual stocks (an increase by 10–14% in 2017 as compared with 2016) confirm the assumption on the decisive role of imported soils in the formation of carbon stocks in the soil constructions of Moscow and emphasize the importance of monitoring and rating of the properties of imported soils as the basis for sustainable development of urban ecosystems.