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The influence of the moisture content on the CO2 emission from peat soils of palsa mires in the discontinuous permafrost area was studied in the north of Western Siberia (Nadym region). The СО2 flux was measured in Histic Cryosols of permafrost peatlands (palsas) and Fibric Histosols of surrounding bog using the closed chamber method for four years at the peak of the growing season (August). Despite a significant difference in the soil moisture (34.8 ± 13.2 and 56.2 ± 2.1% on average), no significant difference in the CO2 emission from these ecosystems was found in any of the observation years; the rates of emission averaged 199.1 ± 90.1 and 182.1 ± 85.1 mg CO2 m–2 × h–1, respectively. Experimental wetting or drying (with a twofold difference in the moisture content) of peat soils at the two sites via their transplantation to a different position showed no significant effect on the CO2 emission even three years after the beginning of the experiment. The absence of significant differences in the CO2 flux between the two different ecosystems was explained by the presence of permafrost and the influence of many multidirectional factors mitigating changes in the CO2 production by soils. An increased CO2 emission from the peat soils of bogs was possible due to the additional contribution of the methanotrophic barrier and the lateral runoff of dissolved CO2 over the permafrost table from the palsa toward the surrounding bog. The absence of response of the CO2 emission to a significant change in the soil moisture content may be indicative of a wide optimum of this characteristic for the microbiological activity of peat soils in the studied region. The obtained data suggest that, while studying CO2 fluxes in cryogenic soils of hydromorphic landscapes, it is necessary to take into account not only biogenic sources, but also other factors, often of a physical nature, affecting the balance of CO2 fluxes and CO2 emission from soils. [ABSTRACT FROM AUTHOR]

In the course of research performed in the continuous and discontinuous permafrost zone of the north of Western Siberia, the values of autotrophic (root) and heterotrophic (microbial) soil respiration and their ratio were estimated for typical ecosystems of the area. The data were obtained on the basis of a complex of field, laboratory, and calculation methods: shading, the root exclusion technique (comparison of emissions at similar sites with and without vegetation), the method of component integration or separate incubation, and the regression method. For soils of plateau palsa, the root contribution to total soil respiration was 16–30% with the use of the shading method and 14 ± 6% under the application of the component integration method. The contribution of root respiration was 60% for soils of shrub–green-moss pine forests and 30% for lichen pine forests. It may be assumed that, in forest ecosystems of the studied area, the contribution of root-derived respiration is even higher, which is related to the undercounting of respiration of tree roots and/or of rhizomicrobial microorganisms and priming effect by some methods. The contribution of root respiration in soils of mound palsa averaged 40%. For tundra with frost-boil ecosystems, the variation in the contribution of root respiration was 15–70%, depending on the location on microelements of cryogenic topography (boils and interboils). All the methods are characterized by disadvantages and some assumptions. These require additional studies to check or correct the data. The interpretation of the results is not always obvious. When using different techniques, similar results were obtained at a large number of replications of experiments during several seasons. The work also presents data on the absolute values of the specific root respiration for different species and size fractions, the value of the root biomass, and the microbial respiration of soils of different permafrost landscapes. [ABSTRACT FROM AUTHOR]

Palsa peatland soils are known as significant terrestrial storage of the Earth's soil carbon. The response of these soils to changing climate may result in a strong feedback to global carbon balance. In laboratory, we investigated the effect of rising temperatures on the upper (T1) and lower (T2) horizons of Turbic Histic Cryosols using sequential (S) and equal-time (ET) methods. The S method was applied to estimate the response of organic carbon mineralization rate (R) to sequential temperature increase from 5 to 30°C; the ET method was used to study the response of the basal (microbial) respiration rate to equal-time incubation at 5, 15, and 25°C. The Q10 coefficient was calculated. In the T1 horizon, both methods (S and ET) demonstrated a positive response of respiration to the rise in temperature. The respiration intensity increased by 91 and 84%, respectively. In the T2 horizon, it increased by 93 and 91%, respectively. However, despite the overall positive response of soil respiration to the rise in temperature, the Q10 values demonstrated differences in the temperature sensitivity of soil respiration. These values were maximal in the cold (5–15°C) range for both horizons. For most of temperature ranges, Q10 was higher for T2 than for T1. For the T1 horizon and S method, Q10 slightly varied (2.7–3.0), whereas in the case of the ET method, it decreased by 3.3 times from the cold (4.9) to the warm 15–25°C (1.5) temperature range. For the T2 horizon, the S method also did not cause significant shifts in Q10 (3.0–3.5); the ET method caused a decrease in Q10 by 1.5 times from the cold (4.3) to the warm (2.8) temperature range. To sum up, the ET method leads to a wider variation of Q10 values in comparison with the S method thus indicating its better applicability for temperature sensitivity studies with palsa peatland soils under laboratory conditions. [ABSTRACT FROM AUTHOR]

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 (Cextr) (32 g C/m2), and microbial carbon (Cmic) (43 g C/m2). Its upper horizon (TO) contained about 50% of the total soil storage of Cmic 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 Cmic (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). [ABSTRACT FROM AUTHOR]