Late Holocene climate change and anthropogenic activities in north Xinjiang: Evidence from a peatland archive, the Caotanhu wetland

Abstract

Climate change and human activities interact to affect the vegetation landscape. We examined the interaction of these drivers using multiproxy records, including data on pollen, charcoal, phytoliths, total nitrogen, total organic carbon, and loss-on-ignition, from a 268-cm sediment profile in Xinjiang, China. By combining these data with information gained from 214 samples of surface pollen assemblages in north Xinjiang, we were able to reconstruct the late Holocene climate using a weighted averaging partial least squares regression model. Our results suggested that the typical desert vegetation of the region changed to Artemisia desert at 2400 cal. a BP, and returned to desert after 900 cal. a BP. A warm–dry and cold–humid climate pattern existed during the past 4000 years. The climate was characterized by obvious fluctuation prior to 2400 cal. a BP, after which it became wetter and colder with little fluctuation. The temperature maximum in our reconstruction occurred around 700 cal. a BP. The macrocharcoal particles reached their highest levels at c. 3500 cal. a BP, and again at 700 cal. a BP, suggesting increases in human activities at these times. An increased amount of anthropogenic plant pollen also appeared in sediment over the past 50 years. Large numbers of Thelypteris spores and Phragmites phytoliths in the surface pollen samples from modern desert vegetation also reflect recent human activities. Therefore, our data provide evidence that both climate and human activities are important drivers of changes in regional vegetation.