A 4000-yr multi-proxy record of Holocene hydrology and vegetation from a peatland in the Sanjiang Plain, Northeast China

Reconstructing historical hydrologic and vegetation conditions can provide useful insights into the mechanisms underlying peatland development and can be used to construct baselines for peatland restoration. In this study, we present numerous physical and biological indices for a 4000-year core from the Honghe National Natural Reserve (HE), a dish-like depression peatland in the Sanjiang Plain of Northeast China. The history of vegetation change was reconstructed by combining plant macrofossils and pollen data from the core, and the water level changes were reconstructed through a multi-proxy study of plant macrofossils, charcoal, stable carbon isotopes, testate amoebae, sediment grain size, loss on ignition, humification degree and magnetic susceptibility. We found that the HE peatland featured wet condition from 4000 to 3600 cal yr BP, which was in accordance with the extreme flooding event at 4.0 ka in northern China. Significant drier shifts were recorded at 3600 and 1200 cal yr BP, while significant wetter shifts were recorded at 2600 and 500 cal yr BP. Factor analysis were applied to all of the proxies to reduce the seven variables to two factors, and the biological indicators, such as plant macrofossils, charcoal and stable carbon isotopes, were found to be more sensitive than the other parameters to water level changes over the last 4000 years. Furthermore, the multi-proxy reconstruction of the wetness of the HE peatland resembles the pattern observed at other sites in Northeast China.