Analysis of the Long-Term Soil Respiration Dynamics in the Forest and Meadow Cenoses of the Prioksko-Terrasny Biosphere Reserve in the Perspective of Current Climate Trends

A combined analysis of the current climate trends and the dynamics of soil respiration under soddy–weakly podzolic sandy-loamy soil (Entic Podzol (Arenic)) in the forest and meadow cenoses in the Prioksko-Terrasny Biosphere Reserve (southern part of the Moscow oblast) is performed. During the observation period (1998–2018), distinct trends of an increase in the average annual air temperature (Tair) and aridity of the summer season as well as a decrease in the duration of stable snow cover are observed. A general trend of a decrease in the total CO2 fluxes from the Entic Podzol (Arenic) under a forest and a meadow for all seasons of the year and throughout the year is also observable on this background. The linear trends of a decrease in the annual and fall seasonal CO2 fluxes from the soils in both cenoses are statistically significant (P < 0.05). Over the 21-year observation period, the monthly average CO2 fluxes from soils have tightly correlated with the average monthly Tair (r = 0.78–0.84, P < 0.001). In dry years, the temperature sensitivity of soils expressed via the Q10 coefficient is by 10–12% lower, than in the years with normal moistening. The average long-term values of annual soil respiration (AnSR) in the forest and meadow cenoses amount to 581 ± 54 and 727 ± 71 g C/(m2 year), respectively, with an interannual variation of 20–22%. The AnSR and summer hydrothermal coefficient are the most closely related explaining 51–56% of the variance in annual CO2 fluxes from soils. The warm season (May–October), which coincides with the period of active plant vegetation, accounts for 73–77% of the AnSR. However, the share of the cold season (November–April) in the annual CO2 flux from soils may reach 38–39% in individual years. Expansion of the network of stationary long-term year-round monitoring of soil respiration is a necessary condition for obtaining both more realistic estimates of the CO2 fluxes from soils and predictions of the ecosystem responses to the current and future climate changes.