Abstract <p>In an old-growth bilberry spruce forest (Republic of Karelia, Kivach Nature Reserve), an assessment of the main components of the carbon cycle was carried out, and the net carbon balance was calculated using a stock-difference method. Based on the data from the forest stand measurement surveys of 2016 and 2022, the net primary production was calculated to be 3.38 t C/(ha year). During 3 years of year-round measurements of CO₂ emissions from the soil surface, estimates of annual CO₂ fluxes were made. The root and microbial respiration was separated. Because of heterotrophic soil respiration, 3.83&#xa0;t C/(ha) year) enters the atmosphere, and due to coarse woody debris (CWD) respiration, it is 0.23–0.71&#xa0;t C/(ha year). An analysis of the influence of environmental factors on the CO₂ emissions of soils was carried out. The seasonal dynamics of soil respiration by 45–50% was determined by soil temperature at a depth of 10 cm. Soil respiration during the cold period from November to April amounted to 15–22% of the annual CO₂ flux, depending on the spruce forest facies. The share of root respiration on average amounted to 27% of CO₂ emissions from the soil surface. Monitoring the formation of net primary production and CO₂ emissions in old-growth forests, as well as an analysis of factors influencing these processes, is of great importance for obtaining both modern carbon balance estimates and predictive estimates made using mathematical modeling methods.</p>