Climatic and hydrological changes in Gaoyou Lake, eastern China over the last millennium, inferred from pollen and grain size records

Abstract

Numerous lakes formed in the area where the Huai River and the Grand Canal converged during the historical period, and it played a substantial role in the evolution of the regional environment. Gaoyou Lake is a vital detention reservoir in the lower reaches of the Huai River. Variations in hydrology and basin-wide environmental changes were analyzed based on pollen assemblages, grain size data, and lithology from sediment cores collected at Gaoyou Lake. This study focused on variations in the hydrodynamic processes of Gaoyou Lake that were responses to changes in climate, regio- nal hydrological events, and human activity. The high percentages of pollen from terrestrial herbs and results of prin- cipal component analysis suggested that the environment of eastern China was arid from AD 900 to 1300 and that this corresponded to the dry conditions of the Medieval Climate Anomaly. The subsequent period between AD 1300 and 1650 was more humid, as revealed by an increase in aquatic pollen and a decrease in grain size. A rise in xerophytic herb taxa (particularly Artemisia and Chenopodioideae) indicated that the climate became arid again from AD 1650 to 1850, during the Little Ice Age. The modern period (AD 1850 onwards) was characterized by another increase in moisture, as reflected by a decrease in herb pollen and grain sizes. The shifts in the course of the Yellow River in AD 1194 and AD 1855 were recorded by abrupt changes in lithology, sediment characteristics, and the percentages of alien pollen taxa. Intense human impacts were demonstrated by cereal-type pollen and an increase in pollen of other cultivated plants such as Cruciferae and Poaceae. This study provides a foundation for further analysis of the dynamic mechanisms between lake development, climate change, and the effects of significant river changes.