Vegetation and climate change over the past 800 years in the monsoon margin of northeastern China reconstructed from n-alkanes from the Great Hinggan Mountain ombrotrophic peat bog

Abstract

n-Alkanes from the Great Hinggan Mountain ombrotrophic peat bog in northeast China record changes in vegetation and climate of the East Asian monsoon marginal region over the past 800yr. At the end of the Medieval Warm period, shrubs and/or sedges were the predominant plants, and the climate was warm and dry. The subsequent appearance of large amounts of Pinus and Sphagnum spp. indicate that climate entered a cold and wet period between 750 and 650calyr BP when the East Asian summer monsoon intensified. Microbial diagenesis increased and diminished n-alkane preservation after 650calyr BP, suggesting that the climate gradually varied from cold and wet to warm and dry conditions. During the period between 500 and 100calyr BP, the climate entered a long period of relatively cold and wet conditions, corresponding to the Little Ice Age. Together with other records, our n-alkane-inferred climate reconstruction in northeast China appears to follow the typical warm/dry and cold/wet changes in East Asia over the past 800yr. Moreover, we propose that temperature-induced evaporation played a more important role than East Asian monsoon precipitation in northeast China over the past 800yr.