Dmitry Alexandrovich Khoroshaev

Soil respiration, which is one of the main fluxes in the global carbon cycle, is characterized by high temporal and spatial variability. Based on the year-round continuous 21-year monitoring of the respiration of soddy weakly-podzolic soil in the forest and meadow coenoses of the southern taiga zone, an assessment of the temporal variability of CO₂ fluxes from soils was made at different time levels: monthly, seasonal, and annual. The values of total respiration of soddy weakly-podzolic soil varied most significantly at the monthly averaging level (coefficient of variation, CV=25–56%), while the variability of the annual respiration of soils was 20–22%. At the seasonal averaging level, the highest variability (CV=39–44%) was noted for winter CO₂ fluxes from soils, whereas the variability of total soil respiration in the other calendar seasons was close and amounted to 26–29%. The effect of the type of cenosis on the total CO₂ fluxes from the soddy weakly-podzolic soil was statistically significant both at the annual averaging level and in all calendar seasons of the year, except for winter. The most stable indicator characterizing the seasonal distribution of CO₂ fluxes within a year is the contribution of the warm period (May–October) to the total annual CO₂ flux from soils, which averages 73–77%. Its variability over 21 years of observation in both coenoses was 8%. It can be recommended to use this indicator to obtain estimates of annual CO₂ fluxes from soils based on field measurements carried out only within the growing season. The numerical experiments performed have shown that continuous measurements of CO₂ emission from soils for five consecutive years reduces the variability of annual and seasonal CO₂ fluxes from soils by more than 2 times compared to a one- or two-year measurement period. This makes it possible to recommend a five-year observation period as the optimal required for obtaining adequate values of annual and seasonal CO₂ fluxes from the soils of the southern taiga zone.