Influence of Meso- and Microclimatic Conditions on the CO2 Emission from Soils of the Urban Green Infrastructure of the Moscow Metropolis

Against the background of global warming, urban ecosystems are becoming increasingly vulnerable to climate stresses. Strategies for climate adaptation developed for almost every major city in the world pay considerable attention to urban green infrastructure as a nature-oriented solution for carbon sequestration. However, the influence of urban climate on the spatiotemporal variability of CO2 emissions from urban soils remains poorly understood, which can lead to inaccurate estimates and inflated expectations of urban green infrastructure in the context of carbon neutrality. In 2019–2022, studies of the dynamics of CO2 emission with parallel monitoring of soil temperature and soil moisture were carried out at three green infrastructure sites of Moscow differing in their mesoclimatic conditions. For each object, plots with different types of vegetation were compared, which made it possible to assess the internal heterogeneity of soil and microclimatic conditions. Soil temperature determined up to 70% of the total variance of CO2 emissions. Mean annual soil temperature in the city center was almost 3–6°C higher than that in the peripheral areas (10–12 km from the center), whereas soil moisture in the center was 10–15% lower. Soils under lawns and shrubs were, on average, 1–2°C warmer and 10–15% wetter than soils under trees. The annual CO2 emission from soils under lawns was, on average, 20–30% higher than that from soils under tree plantations in the same area. At the same time, the differences between the plots with the same vegetation in the center and on the periphery reached 50%, which reflects the high vulnerability of urban soil carbon stocks to mesoclimatic anomalies and the high risks of a further increase in CO2 emissions from urban soils against the background of climate change.