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Alternating influences of the Westerlies and Indian Summer Monsoon on the hydroclimate of the source region of the Yarlung Tsangpo over past 4000 yr

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Frontiers of Earth Science 2023年第4期17卷 933-944页

作者： Zhe SUN Zirui HUANG Kejia JI Mingda WANG Juzhi HOU Institute of Geography and Resources Science Sichuan Normal UniversityChengdu 610066China Group of Alpine Paleoecology and Human Adaptation(ALPHA) State Key Laboratory of Tibetan Plateau Earth SystemResources and Environment(TPESER)Institute of Tibetan Plateau ResearchChinese Academy of SciencesBeijing 100101China CAS Center for Excellence in Tibetan Plateau Earth Sciences Chinese Academy of Sciences(CAS)Beijing 100101China School of Geography Liaoning Normal UniversityDalian 116029China

The Yarlung Tsangpo,the longest river in the southern Tibetan Plateau(TP),has attracted much research attention aimed at understanding the factors controlling its modern hydrology and possible future discharge in the context of ongoing climate ***,partly due to the complex regional climatic background,no consistent conclusions have been reached,especially for its upper *** reconstructions of the source region of the Yarlung Tsangpo can potentially improve our understanding of the history of humidity and its response to climatic *** this study,we used a 97 cm gravity core from Gongzhu Co to reconstruct the hydrology change during the late *** core was dated using AMS ^(14)C and Pb/Cs methods,and we used measurements of element contents(determined by high-resolution XRF scanning),grain size,IC/TOC,and magnetic susceptibility to reconstruct hydroclimatic changes in the source of the Yarlung Tsangpo watershed since~4000 yr *** with a modern meteorological data set,we found that PC1 of the XRF data,the Ca/(Fe+Ti)ratio,and EM1 of the grain size data were indicative of changes in *** records demonstrate a wet interval during~4-1.7 ka BP(ka=1000 yr,BP represents years before 1950 AD),followed by a dry period during since~1 ka *** with independent regional paleoclimatic records revealed shifts in the dominant factors controlling *** wet interval during~4-1.7 ka BP was coeval with a strengthened Westerlies,implying a dominant moisture supply from northern high ***,the extremely low values of Ca/(Fe+Ti)ratio during~4-2.5 ka BP indicate potential glacial freshwater source,which is corroborated by the concurrent high magnetic susceptibility values and increased grain *** rapid drying trend during~1.7-1 ka BP suggests a switch in moisture supply from the Westerlies to the Indian Summer Monsoon(ISM).We attribute the drought conditions after~1 ka BP to a weakened ISM,althoug

关键词： late Holocene humidity changes Westerlies ISM Yarluang Tsangpo

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Environmental changes and Human Impacts on Landscapes near Medieval Steklyanukha-2 Fortress in Russia from Early Iron Age to Modern Times

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Chinese Geographical Science 2023年第1期33卷 69-84页

作者： RAZJIGAEVA Nadezhda GANZEY Larisa KORNYUSHENKO Tatiana GREBENNIKOVA Tatiana KUDRYAVTSEVA Ekaterina PISKAREVA Yana PROKOPETS Stanislav Pacific Geographical Institute Far Eastern Branch of the Russian Academy of SciencesVladivostok 690041Russia Institute of History Archaeologyand Ethnography of the Peoples of the Far EastFar Eastern Branch of the Russian Academy of SciencesVladivostok 690091Russia

The development of landscapes in one of the most populated river basins of the southern Russian Far East was studied using pollen and diatom data. The study sites were a multi-layered mountain fortress, Steklyanukha-2, and an Upper Holocene high floodplain sequence of the Steklyanukha River. Buried soil from the fluvial section acts as an environmental archive of the time in which people from the Yankovskaya archeological cultures settled in the river basin. The soil was formed under conditions of decreasing water supply in the valley and prolonged droughts. Findings of pollen Fagopyrum and Urtica signal economic activity in the Early Iron *** lake sediments accumulated from 1.6 to 0.5 kyr, when the valley was actively developed during the Middle Ages. There are signals of the development of secondary birch and oak forests. In the cultural layer of the fortress and lake sediments formed in the Middle Ages, Ambrosia and Xanthium pollens were found and are reliable evidence of agricultural activity in the valley. The pollens of plants typically seen in human-disturbed areas were also found. Indirect evidence of human activity includes non-pollen *** study of diatoms in a depression near a rampart confirmed the archaeologists' assumption that it was used as a water reserve. Pollen spectra from surface soils reflect agricultural activity in the river basin since the second half of the 19th century. The largest amount of pollen of alien and synanthropic plants and weeds, as well as spores of pathogenic fungi and fire indicators, were found here.

关键词： ancient agriculture mountain fortress humidity changes pollen diatoms

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