Mid-late Holocene hydrological regime on the Sanjiang Plain (Northeast China) in response to East Asian summer monsoon based on a multi-proxy record

The Sanjiang Plain, which is located in mid-high latitudes and monsoon marginal regions. A comprehensive study of long-term hydrological record from climate-sensitive regions is necessary for understanding wetland development and degradation in the context of global warming. This study aims to reconstruct wetland hydrological variations based on multi-proxy during the mid-late Holocene, and to explore how wetland evolution responded to East Asian summer monsoon (EASM). Water level fluctuations in Zhuaji Wetland closely followed changes in EASM intensity during the mid-late Holocene. The grain-size median diameter, sand content and the first principal component scores based on diatom collectively indicated a declining water level caused by the weakened intensity of EASM after the Holocene Climatic Optimum. The diatom record clearly documented key climatic events such as the warm and humid Holocene Climatic Optimum and Medieval Climate Anomaly, as well as the cold and dry 4.2 ka event and Little Ice Age, due to its high sensitivity to hydroclimatic variations. The most dramatic diatom compositional change was the increase in dry-indicating species, Hantzschia amphioxys and Pinnularia subcapitata , which began approximately 300 years ago. Sand content also peaked since 0.3 cal ka BP in Zhuaji Wetland. Intensified human disturbance, primarily through agricultural activities, had led to soil erosion, wetland degradation and diatom diversity destruction on the Sanjiang Plain. This paper presents a multi-proxy (diatom and grain size) record from a natural freshwater wetland on the Sanjiang Plain. The highest water level occurred at 7.5–5.0 cal ka BP. The optimum climate was controlled by the strongest EASM intensity. Since 2.7 cal ka BP, the water level declined continuously, which was caused by the weakening intensity of EASM. It was noticed that the enhanced human disturbance resulted in sharply drying out over the last 300 years. Our results were supported by a series of paleoclimatic records across the monsoonal regions of China. EASM evolution associated with the tropical ocean-atmosphere interactions was initially modulated by the solar insolation. Holocene EASM associated precipitation variations had played an essential role in driving the evolution of wetlands on the Sanjiang Plain. • EASM had played an essential role in driving wetlands evolution. • Climatic deterioration led to a further drying up of wetland after 2.7 cal ka BP. • Human activity caused soil erosion and wetland degradation over the past 300 yr. • Diatom is sensitive to hydroclimatic change which recorded the HO, 4.2 ka, MCA, LIA.