Plant assemblages-based quantitative reconstruction of past mire surface wetness: A case study in the Changbai Mountains region, Northeast China

Abstract

Quantitative relationships between mire plant assemblages and environmental variables have been investigated widely in Europe and North America, but hitherto insufficiently addressed in the East Asian monsoon region. In this study, the plant assemblages of 274 plots along hydrological gradients in five peatlands from the Changbai Mountains region, Northeast China were investigated during the growing seasons (from May to October) from 2014 to 2016. Seven environmental variables of surface water including depth to water table (DWT), pH, electrical conductivity (EC), total nitrogen (TN), total phosphorus (TP), calcium (Ca) and magnesium (Mg) were measured. Canonical correspondence analysis (CCA) indicated that DWT was the principal environmental variable determining the plant assemblages. A transfer function for inferring DWT based on plant assemblages was developed and refined using four models. The transfer function was shown to have strong predictive power following thorough statistical and ecological tests. When the plant assemblages-based transfer function was applied to a 41 cm peat sequence from Laobaishan bog in the Changbai Mountains region, the reconstructed DWTs were essentially consistent, in the trend and vital details of mire surface wetness, with those inferred from a testate amoebae-transfer function, which has been verified to be robust for reconstructing water table in peatlands in the same region. This study suggests that the mire plant assemblages-based transfer function has great potential for quantitative reconstruction of past mire surface wetness, and allows for further research into palaeoclimatology, palaeohydrology and palaeoecology in the East Asian monsoon region using multi-proxy methods.