Abstract In the subtropical monsoon region of China, the climate differs from that of most northern peatlands, where many peatlands have developed in mountainous areas. However, it remains unclear how the carbon dynamics of these subtropical peatlands respond to climate change. Here, we reconstructed the net carbon fluxes of a typical mountainous peatland in Tianmu Mountain, eastern China, over the past thousand years. Humidity and winter temperature are two important climatic factors influencing carbon accumulation (Deviance explained 77.2%) and drought promotes Qianmutian peatland initial development. Despite the decline in carbon accumulation over the last millennium, the peatland’s net carbon balance remains in a ‘carbon sink’ state. This suggests that the risk of carbon release from the peatland carbon pool under natural climate change conditions is not substantial in the subtropical monsoon area. Introduction Peatlands account for only 3 to 4% of the global land area, but their carbon pool accounts for one-third of the global soil carbon pool, storing about 400–600 Gt carbon 1 , 2 , 3 , 4 . The formation of carbon pools in peatlands is intricately governed by the interplay of vegetation production and decomposition processes. Peat accumulation occurs when the rate of production exceeds the rate of decomposition 5 . Climate profoundly influences the thermal and humidity conditions experienced by peatlands, consequently shaping the dynamics of plant organisms 6 , 7 and microbial communities within these ecosystems, which have an impact on the carbon accumulation in peatlands. The response of peatland’s carbon accumulation to temperature and precipitation patterns is linked to the future trajectory of carbon pools within these environments. On a millennial scale, the most notable carbon accumulation in northern peatlands occurred during the early Holocene, a period characterized by gradually rising temperatures 8 , 9 . On a centennial scale, temperature has […]