Changes in vegetation and environment in the Betula microphylla wetland of Ebinur Lake in Xinjiang, China since 3900 cal. aBP.

Abstract

Based on the high resolution record of fossil pollen data from a 190 cm sediment profile collected in a Betula microphylla-dominated wetland of Ebinur Lake in Xinjiang, we aimed to reveal the changes of vegetation and environment in this wetland over the past 3900 years. Results showed that, in the period between 3420 cal. aBP and 3940 cal. aBP, this area was a desert landscape dominated by plants from Chenopodiaceae and Artemisia. During the period of 2830-3420 cal. aBP, this area became a desert steppe dominated by Thelypteris palustris, surrounded by desert plants mainly composed of Chenopodiaceae and Artemisia. In the period between 2640 and 2830 cal. aBP, Typha pollen increased and occupied a dominant position. The area thus became a typical desert intrazonal wetland mainly composed of Typha. In the period between 1200 and 2640 cal. aBP, Phragmites australis began to grow vigorously and became the dominant species. In the period between 660 and 1200 cal. aBP, the population of Betula expanded rapidly, and P. australis plants continued to grow. During the period of 340-660 cal. aBP, the population of B. microphylla became the dominant species, and the abundance of P. australis decreased. However, there was still some P. australis wetlands in the area. Over the past 340 years, as the area of wetlands decreased and the surface water gradually declined, B. microphylla had grown on swampy meadow soils with suitable moisture conditions. In the past 200 years especially, the sharp increases of Chenopodiaceae pollen in palynological assemblage was closely related to the enhancement of human activities and climate change, resulting in the degradation of wetlands and endangerment of B. microphylla. Therefore, it is necessary to strengthen the protection of wetlands and endangered species in this area.