Ecosystem Fluxes and Soil CO2 Emission in a Middle-taiga Spruce Forest under Precipitation Deficit during a Growing Season

The paper presents the measurements results for CO2 concentrations in the air, CO2 net exchange, and CO2 soil emissions in a mid-taiga spruce forest during the growing season of 2023. The seasonal decrease in CO2 in the air above the tree canopy was accompanied by an increase in CO2 net exchange rate. Increased temperatures and a significant precipitation deficit in the summer months had a negative effect on the ecosystem exchange of CO2. The total net exchange of CO2 in the analyzed spruce stand from April 20 to September 30 was –325 g CO2/m2 (–88.6 g C/m2), which was less than in the previous measurements on this territory. The ecosystem respiration in the spruce forest intensified from May to August, and the gross primary production increased from May to July. The ratio of total ecosystem respiration to gross primary production increased from 0.4 in May to 0.9 in August. The maximum values of soil respiration were recorded in July and August. About 1675 g CO2/m2 (457 g C/m2) entered the atmosphere with soil respiration per season, which on average corresponded to 78% of spruce forest ecosystem respiration.