Influence of Forest Growth Conditions on the CO2 Emissions from the Soil Surface in the Middle Taiga Pine Forests of the Komi Republic, Russia

Abstract

Due to large variability in CO₂ emission estimates in different types of forest ecosystems, obtaining experimental data on the respiration of their soils remains relevant. The study aims to characterize CO₂ emission from the soil surface of mature and maturing middle taiga pine forests, taking into account forest conditions. The objects of the study were sphagnum, blueberry, and lingonberry-lichen pine forests located on the territory of the forest field stations of the Institute of Biology, Komi Scientific Center, Ural Branch, Russian Academy of Sciences (Komi Republic, Russia). In 2008–2017, CO₂ emissions were measured by a gas analyzer LI-COR 8100. A brief description of weather conditions for the study period is given. During the snow-free period, relatively high values of CO₂ flux from the soil of pine forests were detected in July (sphagnum pine forests: 1.9–2.9 g C m^–2 day^–1) and August (blueberry and lingonberry-lichen pine forests: 2.5–6.6 g C m^–2 day^–1). The interannual variability of average monthly CO₂ emission and the influence of weather conditions were determined. A close positive relationship between the rate of carbon dioxide emission and soil temperature was revealed (R² = 0.49–0.77). The correlation of CO₂ emission with soil moisture was weak. During the summer months, 188–442 g C m^–2 was released into the atmosphere from the soil of the blueberry pine forest; during the growing season (May 1–September 30), 279–563 g C m^–2; during the snow-free period (May 1–October 31), 308–583 g C m^–2, which is 1.5–1.8 times higher than in sphagnum and lingonberry-lichen pine forests during the snow-free (p = 0.014) and growing season (p = 0.020) periods. No significant influence of forest conditions on C–CO₂ losses in the summer months was found (p = 0.106). Lichen and sphagnum pine forests were comparable in terms of the C–CO₂ flux from the soil surface both during the growing season and the snow-free period (p > 0.05). The data presented are important in determining the expenditure part of the carbon balance in forest ecosystems in the European northeast of Russia.