Regional decadal precipitation reconstructions for the arid and semi-arid zones of northern China were established by the use of different palaeoclimate archives such as ice-cores, tree-rings, lake sediments and writt...Regional decadal precipitation reconstructions for the arid and semi-arid zones of northern China were established by the use of different palaeoclimate archives such as ice-cores, tree-rings, lake sediments and written his-torical documents. Local rainfall reconstructions from single sites were averaged to obtain regional precipitation records for western and eastern regions of an arid and semiarid zone of northern China, respectively. All established regional pre-cipitation curves display 5 dry periods, each lasting about 50 years. Meanwhile, precipitation reconstructions show re-gional dissimilarities. During the last 500 years, the trends of precipitation change in the eastern arid region are basically consistent with those in the western and eastern regions of the semiarid zone. Precipitation variations in the western arid region are unique, showing significant local patterns of rainfall variability. Maximum entropy method (MEM) spec-tral estimates show that each regional precipitation series contains stationary century-scale periodicities of about 120 a. Singular spectrum analysis was applied to isolating the cen-tury-scale oscillation signals from the regional proxy pre-cipitation series. Significant periods with wavelengths of 121.4a, 154.6a, 124.3a, 118.6a, 108.5a and 121.4a were found 26.56%, 26.44%, 28.87%, 18.67%, 33.48% and 34.04% of the variances of the original series for the western arid zone, the eastern arid zone, the whole arid zone, the western semi-arid zone, the eastern semiarid zone and whole northern China, respectively.展开更多
The discovery of Loulan ancient city(LA)in the early 20th century has important significance for understanding the history of Western regions and the Silk Road civilization.The current academic community still has dis...The discovery of Loulan ancient city(LA)in the early 20th century has important significance for understanding the history of Western regions and the Silk Road civilization.The current academic community still has disputes on whether LA was the capital of Loulan Kingdom,the time of its rise,peak and decline,and the process,rate and driving mechanism of human activity change.This study uses the radio carbon dates(^(14)C)database of LA to reconstruct the history of the rise and fall of human activity,and finds that LA experienced more than~500 years from its rise to its peak and then to its decline:1)the city rose rapidly,and the population increased rapidly from~A.D.0 to 230;2)the city was prosperous and flourishing,and the intensity of human activity reached its peak from~A.D.160 to 340,especially in~A.D.230,when the population reached its peak;3)the city accelerated its decline,and the intensity of human activity decreased significantly,and the population shrank rapidly from~A.D.230 to 500;4)LA was completely abandoned after~A.D.560.The results of the ^(14)C dating database do not support that LA was the early capital of the Loulan Kingdom.By comparing the human activity record of LA with the existing high-resolution palaeoclimate records in the surrounding mountainous areas of the Tarim Basin and South Asia,it is found that the superposition of centennial-scale westerly circulation strength events and the~500-year cycle of the Indian monsoon jointly controlled the precipitation and meltwater(snow)supply of the mountains in the Tarim Basin,affecting the changes of surface runoff and oasis area in the basin,which is one of the important factors causing the rise and fall of LA.展开更多
文摘Regional decadal precipitation reconstructions for the arid and semi-arid zones of northern China were established by the use of different palaeoclimate archives such as ice-cores, tree-rings, lake sediments and written his-torical documents. Local rainfall reconstructions from single sites were averaged to obtain regional precipitation records for western and eastern regions of an arid and semiarid zone of northern China, respectively. All established regional pre-cipitation curves display 5 dry periods, each lasting about 50 years. Meanwhile, precipitation reconstructions show re-gional dissimilarities. During the last 500 years, the trends of precipitation change in the eastern arid region are basically consistent with those in the western and eastern regions of the semiarid zone. Precipitation variations in the western arid region are unique, showing significant local patterns of rainfall variability. Maximum entropy method (MEM) spec-tral estimates show that each regional precipitation series contains stationary century-scale periodicities of about 120 a. Singular spectrum analysis was applied to isolating the cen-tury-scale oscillation signals from the regional proxy pre-cipitation series. Significant periods with wavelengths of 121.4a, 154.6a, 124.3a, 118.6a, 108.5a and 121.4a were found 26.56%, 26.44%, 28.87%, 18.67%, 33.48% and 34.04% of the variances of the original series for the western arid zone, the eastern arid zone, the whole arid zone, the western semi-arid zone, the eastern semiarid zone and whole northern China, respectively.
基金supported by the NSFC(Grant No.42071103)the NKRDPC(Grant Nos.2022YFF0801502)+1 种基金the NSFC(Grant Nos.T2192952,41888101)the SPRPCAS(No.XDB26000000).
文摘The discovery of Loulan ancient city(LA)in the early 20th century has important significance for understanding the history of Western regions and the Silk Road civilization.The current academic community still has disputes on whether LA was the capital of Loulan Kingdom,the time of its rise,peak and decline,and the process,rate and driving mechanism of human activity change.This study uses the radio carbon dates(^(14)C)database of LA to reconstruct the history of the rise and fall of human activity,and finds that LA experienced more than~500 years from its rise to its peak and then to its decline:1)the city rose rapidly,and the population increased rapidly from~A.D.0 to 230;2)the city was prosperous and flourishing,and the intensity of human activity reached its peak from~A.D.160 to 340,especially in~A.D.230,when the population reached its peak;3)the city accelerated its decline,and the intensity of human activity decreased significantly,and the population shrank rapidly from~A.D.230 to 500;4)LA was completely abandoned after~A.D.560.The results of the ^(14)C dating database do not support that LA was the early capital of the Loulan Kingdom.By comparing the human activity record of LA with the existing high-resolution palaeoclimate records in the surrounding mountainous areas of the Tarim Basin and South Asia,it is found that the superposition of centennial-scale westerly circulation strength events and the~500-year cycle of the Indian monsoon jointly controlled the precipitation and meltwater(snow)supply of the mountains in the Tarim Basin,affecting the changes of surface runoff and oasis area in the basin,which is one of the important factors causing the rise and fall of LA.
