Historical chemical stability of carbon pool in permafrost peatlands in northern Great Khingan Mountains (China) during the last millennium, and its paleoenvironmental implications

Abstract

The response of carbon pools in peatlands during the last millennium is important for global carbon cycling and is a potential indicator for paleoenvironmental research. Herein, we compared the stability and accumulation of carbon pools between the Hongtu peatland (HT, east site) and the Jintao peatland (JT, west site) in the northern Great Khingan Mountains, spanning the last 700 (HT) and 1000 (JT) years. Peat humification, aromatic and carbohydrate contents, and carbon accumulation rates in these two peat cores were analyzed to better understand the environmental impacts on the stability of carbon pools in these peatlands during the last millennium. The average carbon accumulation rates and the aromatic contents in the HT (23.09 ± 7.28 g C m−2 yr−1 and 28.0 ± 2.2%, respectively) and JT (23.96 ± 6.07 g C m−2 yr−1 and 27.8 ± 0.6%, respectively) were similar. The higher carbohydrate contents in the HT peatland than that in the JT peatland (35.8 ± 2.8% vs 27.8 ± 4.4%) indicated that the stability of carbon pools in the HT peatland were weaker than those in the JT peatland. Local precipitation and fire events may be the two major factors driving the varying stability of carbon pools in these two sites. Especially, at 250–200 cal yr BP, intense fire events may have promoted herb growth and high carbohydrate content in the accumulated plant litter, which ultimately produced higher carbohydrate and lower aromatic contents in the JT peatland than nearby periods. The paleoenvironmental conditions in the studied regions reconstructed by organic matter properties also suggested that the climate forcing mechanisms in the eastern and western sides of the northern Great Khingan Mountains were different and influenced by different degrees by the East Asian monsoon and westerlies.