Abstract <p>We have studied soils of residential and park-recreational (conventional background) zones of the city of Sochi (Black Sea coast of Russia). The recreational zone is allocated to the Sochi Arboretum Park. Natural zonal soils here are represented by brown soils (burozems, Cambisols) and yellow soils (zheltozems, Acrisols), and structural-metamorphic abrazems (Technosols) are formed in the residential zone. The aim of this work is to study the transformation of physicochemical properties of urban soils and the CO₂ emission from them, as well as to identify factors, affecting the intensity of CO₂ emission in urban landscapes of Sochi. Acid–base properties and the composition of the main biogenic elements in soils of the residential zone (Technosols) were transformed under the impact of technogenesis as compared to the background. Alkalinization, an increase in the content of l exchangeable bases, and an insignificant decrease in the humus content are detected in these soils. Measurements of CO₂ emission by the method of closed chambers, using a portable infrared gas analyzer, have shown that the intensity of carbon dioxide flux in soils of the residential zone is, on average, 2.5% lower as compared to that in the park zone. This is related to the transformation of the upper part of the urban soil profile as a result of construction of houses and cultivation of lawns. The variability of CO₂ emission in soils of urban landscapes is high: 48% on average. The main factors of this transformation are the following: (1) soil cultivation using material from humus-accumulative horizons of chernozems and (2) planting of lawn grasses on disturbed soils. Soil CO₂ emission is minimal in natural and natural-like biocenoses under tree vegetation. The climate-forming role of urban soils in Sochi as a source/sink of greenhouse gases should be assessed with due account for all the above-mentioned factors.</p>