Holocene vegetation history and environmental changes inferred from pollen records of a groundwater recharge lake, Badain Jaran Desert, northwestern China

Abstract

Groundwater, rather than regional precipitation, is critical to the development and maintenance of lakes in arid regions. We selected a sedimentary section in the Badain Jaran Desert, northwestern China, where the lakes are mainly groundwater-recharged, to reconstruct past vegetation development and environmental evolution, and to address the driving mechanisms of lake evolution by applying lithological and pollen analyses. Our results show the following: aeolian deposits indicate an extremely dry environment before 11 ka; peat deposition from 11 to 10.2 ka indicates humidification after the Younger Dryas event; limnetic deposits and dry steppe landscape indicate increased humidity from 10.2 to 7.2 ka; lacustrine deposits and dry steppe landscape with few drought resistant plants indicate the highest humidity from 7.2 to 5.4 ka; lacustrine deposits and desert steppe landscape with increasing Ephedra and decreasing Artemisia indicate gradual aridification from 5.4 to 3.6 ka; and shallow lake deposits and abundant drought resistant plants indicate the driest conditions from 3.6 to 0.8 ka. Here, we comparatively analyzed modern hydrologic data from the Badain Jaran Desert and surrounding regional studies of environmental evolution. It was found that the effective moisture changes in the desert, which proved to be different from both the monsoonal area and the region under the influence of westerlies, were controlled by groundwater recharge from glacier meltwater and regional precipitation over the northeastern Tibetan Plateau.