Environmental Evolution And Human Activities Of Typical Wetlands In The Pamir Plateau,Xinjiang Since 5300 Cal A BP

The Holocene’s climate has generally warmed since about 11.7 ka BP,which has given modern humans good chances for survival and economic advancement.At the same time,the natural environment space for human survival has significantly changed with the intensification of human economic and social requirements.The natural wetland in arid and semi-arid areas is a treasure house of plants and animals.As a unique natural complex,it is also one of the locations where human economic and cultural activities are frequent.But because of its fragile ecological setting,it is more vulnerable to the interference of natural environment and human activities.In this paper,the wetlands in the Pamir Plateau of Xinjiang are selected as the research area.Based on chronological framework supported by AMS¹⁴C data and multiproxy records including fossil pollen,grain size,magnetic susceptibility,and organic carbon from two profiles of Kalakuli（KLKL）lake and Jincaotan（LGC）wetland,together with charcoal data of the Zoroastrian temple site（STCN）profile near Jincaotan wetland in Tashkurgan County,the natural environment and human activities of Pamir Plateau in Xinjiang over the past 5300 years have been preliminarily discussed.The results show that:From 820 to 680 cal a BP,many aquatic plants grew in the Kalakuli lake’s shallow water with a desert steppe landscape surrounding it.Between 680 and 500 cal a BP,the area surrounding the wetland changed into a shrub-steppe landscape.The algae plant Spirogyra dominated in the wetland and the magnetic susceptibility and organic carbon value increased quickly during the 500—270 cal a BP period,demonstrating a humid local environment.It suggested that Karakuli lake had experienced the Little Ice Age during this time.The water area has decreased and the environment has progressively dried up since270 cal a BP.Between 5300 and 3750 cal a BP,the local environment of Jincaotan wetland was rather humid,and the aquatic plants were thriving.Since 3750 cal a BP,the environment has also changed due to many dry and wet fluctuations.For instance,the local environment gradually changed from wet to dry during the 3750—1840 cal a BP.The wetland area shrank and the regional vegetation eventually shifted from desert steppe to desert vegetation in the later stage.From 1840 to 810 cal a BP,the regional vegetation returned to desert steppe vegetation.Between 1170 and 730 cal a BP,Medieval Warm Period was recorded in the sediments of Jincaotan wetland,and the values of magnetic susceptibility and organic carbon and the content of wetland plant Cyperaceae all displayed high values in the profile,indicating that the climate and environment at this time were humid.Following that,the regional environment gradually deteriorated,and the surrounding area was desert steppe landscape.Charcoal data of STCN profile near Jincaotan wetland in Tashkurgan County revealed that the historical vegetation near the Jincaotan wetland had been disturbed by humans in the past 1300 years.Since roughly 670 years,the concentrations of total charcoal and large charcoal（>100μm）increased dramatically.Combined with the pollen data of human-influenced vegetation,it demonstrated that there were obvious indications of human activity in the wetland and that the human use of fire has become widespread.Especially in the past 140 years,charcoal concentrations of different size all reached the peak.At this time,the pollen content of human-influenced vegetation and magnetic susceptibility value have also reached the profile’s peak values,indicating that it may be related to the development of local agriculture and frequent wars.This study preliminarily discussed the vegetation and environmental evolution of the Pamir Plateau in Xinjiang since the last 5300 years.Combining with the activity records of ancient ancestors in the area,it revealed the relationship between environmental change and human activities,which may provide a historical background reference for construction of ecological and cultural construction in the area today.