Assessment of the Contribution of Root and Microbial Respiration to the Total Efflux of CO2 from Peat Soils and Podzols in the North of Western Siberia by the Method of Component Integration

Resumo

The method of component integration was tested in the course of studies in typical biogeocenoses of the north of Western Siberia. This method as applied for separate horizons made it possible not only to estimate the contribution of different sources to the total efflux of CO₂ from soils but also to evaluate the participation of horizons in soil respiration. Root respiration contributed to about 14 ± 3% of the CO₂ efflux from the permafrost-affected peat soil (Hemic Cryic Histosol) and to about 29 ± 6% of the CO₂ efflux from the tonguing podzol (Glossic Albic Rustic Podzol (Arenic)). Histosol was characterized by a higher storage of total (organic and inorganic) carbon (26 kg C/m²), extractable carbon (C_extr) (32 g C/m²), and microbial carbon (C_mic) (43 g C/m²). Its upper horizon (TO) contained about 50% of the total soil storage of C_mic and 100% of the total storage of roots (up to 300 g/m²). It had the maximum activity of microbiota and contributed to more than 70% of the total efflux of CO₂ from the active layer (on average, 35 cm in thickness) of Cryic Histosol. Podzol was characterized by the low storage of total carbon (6 kg C/m²), considerable storage of C_mic (38 g C/m²), and much higher microbial activity. This circumstance, together with a tenfold higher storage of the roots (up to 3000 g C/m²) and favorable temperature regime specified high values of the gross production of CO₂ and its emission from the Podzol surface exceeding the corresponding values for the Cryic Histosol by three–five times. The mineral profile of Podzol contributed to about 20% of the total efflux of CO₂ from this soil (on average, about 38 cm in thickness).