Carbon accumulation in West Siberian Mires, Russia Sphagnum peatland distribution in North America and Eurasia during the past 21,000 years

Abstract

The rates of carbon (C) accumulation and the role of fires in the C dynamics of the major types of boreal West Siberian mires were investigated. Detailed analysis of dry bulk density, C, and N concentration and age of the peat layers were used to determine C accumulation rates throughout the Holocene. The average long‐term apparent rate of carbon accumulation (LORCA) at 11 studied sites was 17.2±1.0 (SE) g m−2 yr−1, ranging from 12.1 to 23.7 g m−2 yr−1, and the total apparent carbon sink 11.8 Tg yr−1 (1 Tg = 1012 g) for Russian raised string bogs (68.5 million hectares). These estimates of C accumulation in West Siberian mires are roughly a half of the earlier estimates for these boreal mires. Differences in LORCA for three major mire types in the study area, the ridge‐hollow pine bogs, Sphagnum fuscum pine bogs, and dwarf‐shrub pine bogs, were not significant. The age versus depth (measured as cumulative carbon from the surface downward) curve was slightly convex, indicating a general declining trend in LORCA with decreasing age. About 55% of the present carbon store was already accumulated about 6000 cal. BP. The most intensive expansion phase of the study area occurred between 7000 and 8000 cal. BP. The subsequent lateral expansion has been very slow in the later Holocene. The charcoal data indicated that these mires have burned only 2–3 times during the past 7000–8000 cal. BP, and only a strip of a few meters along the mire margins has burned relatively frequently. No evidence of significant carbon losses due to fires could be found. The charcoal layers at the mire margins suggest a declining trend in burning rates during the later Holocene.