ИСТИНА

The main goal of the study was to obtain new experimental data on seasonal variability of carbon dioxide (CO2) and methane (CH4) fluxes in a subarctic palsa mire, as well as to assess the sensitivity of these CO2 and CH4 fluxes to changes in environmental conditions. Experimental area is situated at the boundary between northern taiga and forest-tundra ecotone at the North of Central Siberia in Turukhansky district of Krasnoyarsk Krai of Russia. The CO2 and CH4 exchange fluxes at out site were continuously measured using the eddy covariance method. Intensive field campaigns were conducted from the late winter (early May) to fall (early October) since 2016 (from snow to snow). The results of field measurements of 2017 and 2018 seasons showed that the mean daily CO2 uptake rates significantly exceeded CO2 emissions for the period between mid-June to the end of August for both seasons, i.e. of the study, and the palsa mire ecosystem in the growing season was served as a sink of CO2 from the atmosphere. Maximum CO2 uptake rate (about 4.5 gC m-2 d-1) were observed in July mainly due to high incoming photosynthetically active radiation (PAR) and optimal air temperature and soil moisture conditions. In the late August the balance between CO2 uptake and CO2 emissions was approaching zero. NEE values in September were positive demonstrating net efflux of CO2 to the atmosphere. Temporal variability of CH4 fluxes was relatively high and varied between -28 to 74 mgC m-2 d-1. Such variability was mainly associated with weather conditions, peat aeration, vegetation growth and functioning, nutrient level, peat temperature and microbial processes responsible for net release of CH4.