Mullahingamise sesoonne dünaamika kuusikute aegreas / Seasonal dynamics of soil respiration in a chronosequence of the Norway spruce stands

Soil respiration resulting from microbial and root respiration is a major component of the forest carbon cycle. The response of soil respiration to varying environmental factors (soil temperature and soil moisture) was studied in a Norway spruce chronosequence composed of four age classes (4, 27, 36, and 84 year old) on Gleyic Podzol. Soil respiration was measured monthly with closed dynamic chamber system, soil temperature and soil moisture were measured simultaneously. Mean soil respiration rate averaged over three years was 3.3 μmol CO2 m^-2s^-1, ranging from 0.6 to 5.4 μmol CO₂ m^-2s^-1, with the maximum occurring in August and the minimum in December. Stand age had a significant effect on soil respiration: the highest respiration rate was found in 27-year-old stand. Over three years an exponential relationship between soil respiration and soil temperature accounted for 68-81% of the seasonal variation, Q₁₀ (the factor by which the respiration rate differs for a temperature interval of 10 °C) for the individual stands ranged between 4.4 and 5.4. The influence of soil moisture content on soil respiration was weak and revealed in dry conditions only. The results of this study can be used to help understand and predict the effect of harvest on soil respiration and how the respiration might respond to changing climate conditions.