Holocene climate background for lake evolution in the Badain Jaran Desert of northwestern China revealed by proxies from calcareous root tubes

It has been unclear whether Holocene lake evolution in the Badain Jaran Desert of northwestern China, an area in which lakes are mainly recharged by groundwater, responded to climate change. In this study, we analyzed the Mg/Ca ratio and phytolith assemblages from 10 Holocene calcareous root tube samples from the desert to reconstruct changes in effective moisture and mean annual precipitation (MAP) at the millennial scale during the Holocene and to explore the factors affecting lake evolution. Our results revealed that the effective moisture at 7000-5000 cal yr BP was higher than that of 5000-2000 cal yr BP. Similarly, the MAP was higher at 7000-5000 cal yr BP (175 +/- 37 to 205 +/- 37 mm) than at 5000-2000 cal yr BP (145 +/- 37 to 165 +/- 39 mm). The expansion of the lakes during the Early Holocene would have resulted from the input of groundwater from the meltwater in the recharge area. High lake levels in the Middle Holocene corresponded to increased monsoonal precipitation and groundwater recharge. The gradual decline of lake levels in the Late Holocene indicated a relatively arid climate with decreased monsoonal precipitation and groundwater recharge.