Effect of Moisture on CO<sub>2</sub> Flux of the Palsa Mire Soils (North of Western Siberia)

Abstract

The effect of the moisture content on peat soils has been studied in discontinuous permafrost area in the north of the Western Siberia (Nadym region). СО2 flux was measured in palsa mire soils (Cryic Histosol) and surrounding bogs (Fibric Histosol) using the closed chamber method for 4 years at the peak of the growing season (August). Despite a significant difference in soil moisture (34.8 ± 13.2 and 56.2 ± 2.1% on average), no significant difference in CO2 emission between these ecosystems was found in any of the observation years (on average 199.1 ± 90.1 and 182.1 ± 85.1 mg CO2 m–2 h–1, respectively). Experimental wetting or drying (with two times difference in moisture content) of peat soil plots by transplantation method showed no significant effect on CO2 emission even 3 years after the experiment start. The absence of significant differences in CO2 flux between ecosystems and experiments was explained by the presence of permafrost and the influence of many multidirectional factors mitigating changes in CO2 production by soils. CO2 flux enhancing from the soils of the bog is possible due to the additional contribution of the methanotrophic filter, as well as the lateral runoff of dissolved CO2 over the permafrost table from palsa mire surrounding the bogs. The absence of a response of CO2 emission to a significant change in moisture may indicate a wide optimum of this parameter for microbiological activity in peat soils of the studied region. The results indicate that, in the study of cryogenic soils of hydromorphic landscapes, it is necessary, in addition to biogenic sources, to take into account additional factors, often of a physical nature, that change the balance of CO2 fluxes and CO2 emission by soils, respectively.