Nutrient inputs control the carbon sequestration efficiency of peatlands in the northern margins of the East Asian Summer Monsoon

The peatlands at the northern margins of the East Asian Summer Monsoon (EASM) are an important carbon pool for the global carbon cycle. However, the major factors that influence the carbon flux and carbon sequestration of these peatlands remains unclear. In this study, we investigate the carbon flux and carbon sequestration history of the Gangwayao peatland at the northern margins of the EASM to explore these issues. Macrofossil evidence indicates that this peatland developed from a fen to a bog over the past 4700 years. Carbon flux parameters, such as net carbon pool (NCP) representing the carbon sequestration potential, net carbon uptake (NCU) representing carbon input, net carbon release (NCR) indicating carbon loss and net carbon accumulation rate (NCAR) of this peatland were mainly controlled by nutrient inputs. Additionally, correlation analysis suggested that the NCU has significant impact on the NCAR and NCAR, further affecting the NCP. The NCU and NCAR were controlled by nitrogen and phosphorus inputs released by human activity and tephra deposition. The carbon sequestration modes in the study area can be identified as two types. The first type is a high carbon sequestration efficiency mode, when human activities and frequent volcanic eruptions provided nutrients such as nitrogen and phosphorus, which promoted the high productivity of peat vegetation and the high carbon sequestration efficiency of the peatland. The second type is a low carbon sequestration efficiency mode, when fewer nutrient additions from human activities resulted in low productivity of peat vegetation and the low carbon sequestration efficiency of the peatland. These results extend our understanding of the connections between human activity, volcanic activity and carbon sequestration in peatlands, which provide a foundation for future predictions of the carbon sequestration potential of peatlands at the northern margins of the EASM.