Enhanced human activities have disturbed the vegetation-climate relationship over the last millennium in the Changbai Mountains, north-east China

Understanding long-term regional anthropogenic impacts on vegetation can enhance our knowledge of natural environmental development. In this study, a 140-cm-long peat core covering the last ∼2850 years collected from the Changbai Mountain range was analysed for pollen and charcoal, to reconstruct vegetation and fire history, and to investigate the intensity and effects of human activities. Results show that the forest gradually shrank as precipitation decreased before around 1000 cal yr BP, characterised by the relative changes between Pinus and broad-leaved taxa. Over the last millennium, the forest further shrank, with broad-leaved components relatively increasing and herbaceous species significantly expanding at the cost of Pinus. Human activities in the Changbai Mountains have intensified since 1500 cal yr BP, as inferred from the increase in anthropogenic pollen indicators, along with a rise in both the frequency and intensity of palaeofire. Notably, human activities via the selective felling of Pinus and facilitation of the expansion of herbaceous species have disturbed the vegetation-climate relationship and thus introduced a bias into pollen-based climate reconstructions covering the last millennium. Additionally, human activities increased the frequency and intensity of palaeofire, with a significant contribution of local fires. We highlight that in the context of enhanced anthropogenic impact on the natural vegetation, pollen-based palaeoclimate reconstructions should be approached carefully.