Environmental changes recorded by multiple indices in Erxianyan wetland in the past 1900 years, Central China

Abstract

The past 2000 years represent an important period of climate change. The Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA) have attracted much attention, but the start and end times and humidity characteristics of these climate stages are still controversial. Here, we present a lacustrine sediment record from the Erxianyan wetland in central China covering a timespan of 1900 years. The pollen, grain size, total organic carbon (TOC) content, total nitrogen (TN) and carbon-to‑nitrogen ratio (C/N) analyses of the sediments derived from the Erxianyan wetland revealed the vegetation and climate changes that have occurred in central China over the past 1900 years. From 70 to 740 CE, the water level was high, the organic matter content of the lake reached a high level, and many plants surrounded the lake. The climate was warm and humid. From 740 to 1150 CE, the forest coverage increased, the fern coverage decreased, and the lake water volume decreased. The climate gradually changed from humid to dry. From 1150 to 1990 CE, the vegetation coverage around the lake decreased, the tree proportion declined, and the proportions of terrestrial herbs and ferns increased. The climate was cold and dry. The climate change characteristics reflected in the EXY profile roughly correspond to the Qin-Han Warm Period and Sui-Tang Warm Period. The MCA was warm and dry, while the LIA was cold and arid. Based on comparisons with other climate records and modern precipitation records, we found that the Erxianyan climate changes over the past 1900 years may have been affected by the combined effects of solar radiation, the El Niño-Southern Oscillation (ENSO) and the East Asian Summer Monsoon (EASM). These results also confirm the complexity of the climate in the middle and upper reaches of the Yangtze River during the MCA and the LIA. • In the past 1900 years, the climate in this region has shown a trend of becoming colder and drier. • The characteristics of MCA were warm and dry. • LIA was characterized by cold and arid. • Climate change in Erxianyan in the past 1900 years may be affected by the combined effects of solar radiation, ENSO and EASM.