Nadezhda Dmitrievna Ananyeva

Urban soils contain a substantial pool of organic matter (OM), the decomposition of which leads to intensive CO₂ emission that important in terms of global climate change. The OM decomposition increases in line soil temperature, the magnitude of such effect largely depends on the soil physicochemical properties. At the same time, the contribution of the functional microbial diversity on the temperature sensitivity of OM decomposition (Q₁₀) is still poorly understood, and especially for urban ecosystems. Consequently, our study aimed to assess the effect of the microbial functional diversity on the Q₁₀ value for urban soils considering its physicochemical properties. In the St. Petersburg, Moscow, Voronezh and Krasnodar, located in different bioclimatic zones (southern taiga, mixed forests, forest-steppe and steppe, respectively), four parks were selected. In each park the samples were taken from the topsoil (0-10 cm layer). In soil samples, decomposition of OM was determined at the temperature 10, 20, 30, and 40°C for the subsequent calculation of Q₁₀ value. The soil physicochemical (moisture, texture, pH, content of C, N, P₂O₅, K₂O) and microbial (functional diversity, biomass) properties were determined as possible Q₁₀ index drivers. The Q₁₀ value in humus horizons of urban soils was mainly correlated with its texture, moisture C and N contents, while the microbial functional diversity was correlated with P₂O₅. The regular distribution pattern of Q₁₀ and the studied soil properties of urban parks along the latitudinal gradient has not been found, however a negative relationship between Q₁₀ and the microbial functional diversity has been revealed (R² = 0.50). Apparently, the high microbial functional diversity contributes to a decrease of the temperature sensitivity of OM decomposition.