Soil Respiration in a Sphagnum Pine Forest in the Komi Republic: Interannual Variation, Contribution of Root Respiration and Correlation with Weather Conditions

Assessing soil respiration (Rs), partitioning it into autotrophic and heterotrophic components, identifying predictors for modeling soil C flux, and establishing continuous monitoring are key tasks for characterizing forest ecosystem carbon cycles. This study describes Rs of Histic Gleyic Rustic Podzols (Arenic) under middle-taiga dwarf- shrub–sphagnum pine forest in the Komi Republic. Soil respiration rates were measured from May to October at the Lyalsky test site using LI-8100 and EGM-5 gas analyzers. During the warm period, the highest soil respiration rates (5.6–6.8 gC/(m2 day)) occurred in August, driven by soil warming and a high contribution from root respiration. Soil temperature at 10 cm depth positively influenced Rs (r = 0.42–0.90) though the relationship weakened during summer. Soil moisture has a negative effect on Rs. The Q10 coefficient ranged from 4.5 to 7.1 over the entire warm season, decreasing by 23–51% in summer. Correlation analysis with meteorological data from the Ust-Vym weather station revealed a strong relationship between Rs and mean air temperature over the preceding 96 h (R2 = 0.72, p < 0.001), from which we derived a regression equation. No relationship was found with precipitation. Using soil temperature measured in the pine forest and the Van’t Hoff equation, we estimated the cumulative soil CO2 efflux from May to October at 568–684 g C/m2, with summer months accounting for 68%. Root respiration contributed an average of 40% to CO2 emissions from June to October. Cumulative C–CO2 fluxes, modeled using either pine forest soil temperature or weather station air temperature as predictors, showed high comparability. This highlights the substantial potential of meteorological data for modeling cumulative soil CO2 fluxes in Rs monitoring programs.