Estimation of Organic Carbon Stocks in the Urban Soils of the Rostov Agglomeration

The article presents the results of the study and calculation of specific reserves of organic carbon in the residential, recreational, and industrial zones of the cities in the Rostov agglomeration core. The results are based on the analysis of soil samples taken from more than one hundred soil pits and boreholes, as well as more than 500 samples from the surface ten-centimeter-thick layer. The carbon content was determined by dry high-temperature catalytic combustion. The average content of organic carbon in the upper (layer of 0–10 cm) soil horizons was determined (3.89 ± 1.11%). Its change was recorded depending to which functional zone it belonged. The highest content of 4.24 ± 0.85 was noted in the soils of the park and recreational zone (city parks, squares, and forest parks), and the lowest was in the residential and fallow areas of the agglomeration (2.35 ± 0.92 and 2.80 ± 0.64, respectively). The analysis of its specific reserves (per unit area) was carried out, and soil combinations, the most and the least abundant in organic carbon, in various functional zones were identified. The park recreational and industrial zones of the city have the largest specific reserves of carbon (52.18 ± 10.42 and 63.35 ± 17.81 t/ha, respectively), while the residential and fallow areas have the lowest (38.75 ± 15.25 and 31.68 ± 7.28 t/ha). In the cities of the steppe zone of European Russia, the soil cover of urban forests plays a special role in terms of its storage of the organic carbon pool. The organic carbon content in the 10–100 cm layer within the core of the Rostov agglomeration averages 1.30 ± 0.73%. It showed no statistically significant differences in organic C content and stocks when comparing soils of different land use types. The comparison of carbon reserves in the one-meter-thick soil layer of the city with the literature data on chernozems of the steppe zone show similar values. The results of the study will allow us to assess the role of urban soils in the regional carbon balance particularly when planning measures to reduce greenhouse gas emissions.