Carbon Accumulation in Peat Soils of Floodplain Mires in the Northeast of the Central Russian Upland

Abstract

Peat deposits of the Bol`sheberezovskoe and Podkos`movo floodplain mires formed during the Atlantic–Subboreal periods of the Holocene in the Nepryadva River valley in the northeastern part of the Central Russian Upland have been studied. Data on the botanical composition of peat indicate that the genesis of these mires was associated with eutrophic paleocenoses, which accumulated carbon at a rate of 21.8–95 g/m² per year. The formed eutrophic peat was characterized by a high degree of decomposition (45–55%) and by a low rate of vertical growth (on average, 0.3–0.6 mm/year), which was due to the seasonal dynamics of the level of mire waters. The carbon content of peat is 14% for the Podkos`movo mire and 31% for the Bol`sheberezovskoe mire. The differences are due to the specific water–mineral nutrition of the mires: the high carbonate and ash contents of the Podkos`movo mire. Carbon stocks in peat soils of floodplain mires vary from 51.5 up to 125 kg/m<sup>2</sup> for 10-cm-thick horizons. This parameter is determined by the degree of decomposition of plant residues, which depends on the composition and structure of microbial complexes. The microbial complex of Bol`sheberezovskoe and Podkos`movo mires is dominated by the fungal and bacterial components, respectively. This is the reason for the differences in the microbial biomass of the mires: 222 g/m<sup>2</sup> for the Podkos`movo mire and 898 g/m² for the Bol`sheberezovskoe mire. The differences between the two floodplain mires are related to the degree of variation in the level of mire waters during the growing season, which is more considerable at the Bol`sheberezovskoe mire because of its artificial drainage. Floodplain mires are important depots of atmospheric carbon, and the intensity of its accumulation is determined by a combination of factors.