Pollen Assemblages And Palaeoenvironment Change In The Typical Wetland Of North Xinjiang, China

With the increasing deterioration of the ecological environment, the study on land desertification has been paid close attention in the world. Study of Holocene environmental change became more complicated due to the unreasonable utilization of water resources and the considerable reduction of wetland.The reliable pollen data supply the valuable and usefull information for quantitative reconstruction of vegetation and climatic parameters of past relative periods.A comparison between modern pollen spectra and fossil pollen data can help us to obtain a quantitative description of the Holocene paleoclimate and paleovegetation history. On the basis of the results of analyses of spores and pollen, and chronologic datings in Ebinur and Kanas profile, the climate changes and paleovegetation are reconstructed. According to the data of vegetation plots and pollen assemblages of 49 modern pollen samples, which were collected along the Bortala River Basin(Xinjiang,China), we analyzed the relationship between vegetation and surface pollen assemblages. The 49 surface samples were divided into six pollen zones(alpine meadow zone, subalpine meadow and steppe zone, forest-shrub zone, shrub steppe zone, desert steppe zone, desert vegetation zone) based on modern vegetation data and characteristics of the surface pollen spectra. And the pollen spectra of Kanas region could be divided into 3 pollen zones(low mountain desert, mountain grassland belt,forest), from the aspects of eastern slope and western slope of desire.We examined the interaction of climate change and vegetation change using multiproxy records from the sediment profile of Ebinur and Kanas in Xinjiang. Combining with 214 surface pollen data, we were able to reconstruct climate in these two areas using a weighted averaging partial least squares regression(WAPLS) model.Our results show that a warm-dry and cold-humid climate pattern existed during the past cal 3000 years both in Ebinur and Kanas. A cold and humid climate condition existed before cal 1300 a BP in study areas. Since cal 1300 a BP, the climate became warm and dry. The vegetation was desert steppe and steppe during the past cal 3000 a BP in Ebinur area. A lot of Betula grew in the wetland in 360 cal a BP, and greatly reduced after 180 cal a BP. At about cal 380 a BP, the climate became cold and wet with a dramatic increase in Picea and Abies in Kanas.Additionally, contrasting with vegetation and climate change in Ebinur and Kanas is recently a diagnostic tool to validate climate in different land-form areas. As the kidney of the eartn, the study of wetland can contribute to the ecologicalcivilization construction in Xinjiang because of its buffering capacity of climate change.