Permafrost peatland development at thermokarst lake margins in the northern Greater Khingan Mountains of Northeast China: Rapid areal increase and carbon accumulation since the 1950s

Abstract

Peatlands are major carbon sinks and play a crucial role in the carbon cycle. Permafrost peatlands in mid-to-high latitude regions are highly sensitive to climate change, leading to the formation of thermokarst lakes in widely distributed areas of permafrost degradation. In this study, seven peat cores from typical peatlands at thermokarst lake margins in the northern Greater Khingan Mountains of northeast China were used to reconstruct the formation age and accumulation history of peatlands, and to analyze the change in the stability of the peatland carbon pool over time. Results show that drought events and local topography influence the lakeward expansion of the peatlands at thermokarst lake margins, with expansion rates ranging from 2 cm yr⁻¹ to 32 cm yr⁻¹. Strongly influenced by hydrological fluctuations and warming, the carbon accumulation of the studied peatlands commenced with a stage of slow accumulation, and then entered a rapid accumulation stage after the 1950s, with the carbon accumulation rates increasing from 45.2 ± 5.5 g C m⁻² yr⁻¹ to 330.5 ± 14.4 g C m⁻² yr⁻¹. Moreover, the stability of the peatland carbon pool has improved with more stable aromatic compounds increasing from 29.3 % to 32.3 %, as peat accumulation has entered a rapid accumulation stage.