Seasonal and Annual Variations in Soil Respiration of the Artificial Landscapes (Moscow Botanical Garden)

Cities emit 30–40% of total greenhouse gases emissions and are responsible for 45–70% of total energy-related CO2 emissions. CO2 fluxes in cities consist of a complex balance of biogenic and anthropogenic sources. Despite the evidence that biogenic urban CO2 fluxes can be important, we still know little about the magnitude of the urban biogenic CO2 flux. Our study included two main tasks: (1) estimation of annual carbon dioxide efflux by urban forest soils the case of the Botanical Garden arboretum (Lomonosov Moscow State University) and the assessment of its seasonal dynamics; (2) to identify the factors responsible for the annual and seasonal variations of soil respiration. Studies were carried out on the two stationary plots with plantations of Picea obovata (spruce) and Carpinus betulus (hornbeam) from 2014 to 2017 years (starting in October). Annual CO2 flux depending on the year and type of plantation was from 1750 to 3180 g CO2 m−2 yr−1. Summer period (when the soil temperature at 10 cm depth was above 10 ℃) was more than half the annual soil CO2 efflux. In the seasonal aspect, the role of abiotic factors (soil temperature and moisture) in the dynamics of soil respiration is different. Soil temperature plays a key role in the dynamics of soil respiration during the mid-seasons (spring and autumn). When the soil temperature reaches 10 ℃, its role decreases, the soil moisture becomes the determining (limiting) factor. In the winter, early spring and, possibly, late autumn periods, other factors and processes may be leading, such as soil freezing-thawing, pronounced gas diffusion and dissolution.