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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]

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]

Statistical analysis of a vast body of data collected during five field seasons (2011-2015) was performed to characterize the biological activity of soils in the northern taiga ecosystems of Western Siberia. Automorphic forest soils, hydromorphic (oligotrophic bog) soils, and semihydromorphic (flat-topped and large peat mounds) soils were characterized. Statistically significant differences of average levels of CO2 emission from the soils were identified at the ecosystem level. The CO2 emission from podzols of automorphic forest ecosystems at the peak of the growing season (205 ± 30 to 410 ± 40 mg CO2/(m2 h)) was significantly higher than the emission from semihydromorphic soils of peat mounds (70 ± 20 to 116 ± 10 mg CO2/(m2 h)). The presence and depth of permafrost was a significant factor that affected ecosystem diversity and biological activity of northern taiga soils. Statistically significant differences in the total, labile, and microbial carbon pools were observed for the studied soils. Labile and microbial carbon pools in the organic layer (10 cm) of forest podzols amounted to 0.19 and 0.66 t/ha, respectively; those in the organic layer (40 cm) of peat cryozems of flat-topped peat mounds reached 1.24 and 3.20 t/ha, and those in the oligotrophic peat soils (50 cm) of large peat mounds were 2.76 and 1.35 t/ha, respectively. The portion of microbial carbon in the total carbon pool (Cmicr/Ctot, %) varied significantly; according to the values of this index, the soils were arranged into the following sequence: oligotrophic peat soil < peat cryozem < podzol. [ABSTRACT FROM AUTHOR]

In the discontinuous cryolithozone in the north of Western Siberia in forest and tundra biogeocoenoses, two field methods for individual determination of root and microbial soil respiration were tested: plant shading and root exclusion (comparison of the plots with vegetation and without it). The proportion of of root respiration in the total soil respiration in the forest biogeocoenosis was 7-50%; in the tundra, 10-50%. The plant shading method has been physiologically substantiated, is the least time-consuming, and the least damaging to soil function (moisture and temperature do not change). The proposed modification of the method (root exclusion on natural objects) demonstrated a satisfactory result, but it is not universal due to the specifics of objects. [ABSTRACT FROM AUTHOR]

Permafrost and varying land surface properties greatly complicate modelling of the thermal response of Arctic soils to climate change. The forest-tundra transition near Nadym in west Siberia provides an excellent study area in which to examine the contrasting thermal properties of soils in a forested ecosystem without permafrost and peatlands with permafrost. We investigated the effects of forest shading, snow cover and variable organic soil horizons in three common ecosystems of the forest-tundra transition zone. Based on the year-round temperature profile data, the most informative annual parameters were: (1) the sum of positive average daily temperatures at depths of 10 and 20 cm; (2) the maximum penetration depth of temperatures above 10 °C; and (3) the number of days with temperatures below 0 °C at a depth of 20 cm. The insulative effect of snow cover in winter was at least twice that of the shading and cooling effect of vegetation in summer. In areas with shallow permafrost, the presence of a thick organic horizon, with an extremely low thermal diffusivity, creates a very steep temperature gradient that limits heat penetration to the top of the permafrost in summer. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]