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Sedimentary and OSL dating evidence for the development of the present Hobq desert landscape, northern China

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Science China Earth Sciences 2013年第12期56卷 2037-2044页

作者： FAN YuXin CHEN XiaoLong FAN TianLai JIN Ming liu jianbao CHEN FaHu Key Laboratory of Western China's Environmental Systems (MOE) Lanzhou University School of Earth Sciences & Key Laboratory of Mineral Resources in Western China (Gansu Province) Lanzhou University

The sedimentary sequence and landscape of the Hobq desert was observed through twelve profiles along five N-S sections extending through the entire desert.Aeolian sands were found to overlie the alluvial,diluvial,and lacustrine sediments in this desert.Optically stimulated luminescence(OSL)dating results were obtained from post-IR OSL signals of quartz fractions of sand samples at the bottom of sand dunes and hills by using the Double-SAR protocol.The OSL ages reveal that the latest sand accumulation began around 19 ka in the northwestern part and 9 ka in the eastern part of the Hobq Desert.Around 7 ka,the sand accumulation was strengthened and extended southward and northward 2 ka to develop the present desert landscape.Our study suggests that the aeolian sand accumulation around 19,9 and 7 ka resulted from the weakening of the Asian summer monsoon over this region.However,the rapid development of the present Hobq desert landscape since 2 ka was likely triggered by human activities in this desert.

关键词：光释光测年沙漠景观中国北方沉积岩证据库布齐沙漠亚洲夏季风沉积层序

On the timing of the East Asian summer monsoon maximum during the Holocene—Does the speleothem oxygen isotope record reflect monsoon rainfall variability?

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Science China Earth Sciences 2016年第12期59卷 2328-2338页

作者： CHEN JianHui RAO ZhiGuo liu jianbao HUANG Wei FENG Song DONG GuangHui HU Yu XU QingHai CHEN FaHu Key Laboratory of West China s Environmental System(Ministry of Education) College of Earth and Environmental SciencesLanzhou University Department of Geosciences University of Arkansas Institute of Nihewan Archaeology Research Hebei Normal University

The evolution of the East Asian summer monsoon(EASM) during the Holocene has long been of significant interest.Knowledge of past EASM variability not only increases our understanding of monsoon dynamics on a long timescale,but it also provides an environmental and climatic background for research into Chinese cultural development.However,the timing of the EASM maximum remains controversial.The popular concept of an "early Holocene maximum" is mainly based on speleothemδ18O(δ18Oc) records from caves in southern China;however,the interpretation of δ18OCas a reliable proxy for EASM intensity is being increasingly challenged.The present paper is a critical review of the climatic significance of the δ18OCrecord from China.Firstly,we suggest that precipitation in northern China is an appropriate index of EASM intensity,the variation of which clearly indicates a mid-Holocene monsoon maximum.Secondly,an interregional comparison demonstrates that the precipitation record in northern China is quite different from that in southern China on a range of timescales,and is inconsistent with the spatial similarity exhibited by speleothem oxygen isotope records.Furthermore,both modeling and observational data show that the δ18OCrecords from southern China indeed reflect changes in precipitation δ18O(δ18OP) rather than precipitation amount,and therefore that their use as an EASM proxy is inappropriate.Finally,we address several significant monsoon-related issues-including the driving mechanism of the EASM on an orbital timescale,the climatic significance of speleothem oxygen isotopes,and the relationship between atmospheric circulation and precipitation in monsoonal regions.

关键词： East Asian summer monsoon Holocene Speleothem oxygen isotopes

Humid Medieval Warm Period recorded by magnetic characteristics of sediments from Gonghai Lake, Shanxi, North China

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Chinese Science Bulletin 2011年第23期56卷 2464-2474页

作者： liu jianbao CHEN FaHu CHEN JianHui XIA DunSheng XU QingHai WANG ZongLi LI YueCong Key Laboratory of Western China's Environmental System (Ministry of Education) Lanzhou University Lanzhou 730000 China College of Resources and Environment Hebei Normal University Shijiazhuang 0500161 China

Variations in monsoon strength, moisture or precipitation in eastern China during the MWP reflected by different climatic records have shown apparent discrepancies. Here, detailed environmental magnetic investigations and mineralogical analyses were conducted on lacustrine sediments of Core GH09B1 (2.8 m long) from Gonghai Lake, Shanxi, North China, concerning the monsoon history during the MWP. The results demonstrate that the main magnetic mineral is magnetite. The sediments with relatively high magnetic mineral concentrations were characterized by relatively fine magnetic grain sizes, which were formed in a period of relatively strong pedogenesis and high precipitation. In contrast, the sediments with low magnetic mineral concentrations reflected an opposite process. The variations of magnetic parameters in Gonghai Lake sediments were mainly controlled by the degree of pedogenesis in the lake drainage basin, which further indicated the strength of the Asian summer monsoon. The variations in the and S 300 parameters of the core clearly reveal the Asian summer monsoon history over the last 1200 years in the study area, suggesting generally abundant precipitation and a strong summer monsoon during the Medieval Warm Period (MWP, AD 910–1220), which is supported by pollen evidence. Furthermore, this 3–6-year resolution environmental magnetic record indicates a dry event around AD 980–1050, interrupting the generally humid MWP. The summer monsoon evolution over the last millennium recorded by magnetic parameters in sediments from Gonghai Lake correlates well with historical documentation (North China) and speleothem oxygen isotopes (Wanxiang Cave), as well as precipitation modeling results (extratropical East Asia), which all indicate a generally humid MWP within which centennial-scale moisture variability existed. It is thus demonstrated that environmental magnetic parameters could be used as an effective proxy for monsoon climate variations in high-resolution lacustrine sediments.

关键词：湖泊沉积物中世纪暖期磁性矿物中国北方潮湿特征记录山西季风强度

Dust storms in northern China and their significance for the concept of the Anthropocene

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Science China Earth Sciences 2022年第5期65卷 921-933页

作者： jianbao liu Jie CHEN Shengqian CHEN Xinwei YAN Haoran DONG Fahu CHEN Key Laboratory of Western China’s Environmental Systems(Ministry of Education) College of Earth and Environmental ScienceLanzhou UniversityLanzhou 730000China Group of Alpine Paleoecology and Human Adaptation(ALPHA) State Key Laboratory of Tibetan Plateau Earth SystemResources and Environment(TPESRE)Institute of Tibetan Plateau ResearchChinese Academy of SciencesBeijing 100101China

A key scientific issue in the study of the Anthropocene is the determination of the corresponding stratigraphic marker in geological archives.The arid and semi-arid regions of Asia are the second largest dust source on Earth,and their release,transport and deposition of dust affect global climate change,as well as marine and terrestrial biogeochemical cycles.Over the past~2000 years,human activity has outpaced natural climatic variability as the dominant control of dust storms in northern China.Thus,exploring the potential of anthropogenic Asian dust as a marker of the Anthropocene and its impacts on lake ecosystems may contribute to an improved definition of the characteristics and timing of the Anthropocene.In this context,we measured spectrally-inferred chlorophyll a from the sediments of an undisturbed alpine lake in northern China,and compared the results with dust storm data from the same cores and with regional climatic records.Asian dust is a widely distributed,globally significant signal of human activity,and it is also well preserved in various geological archives;hence,we propose anthropogenic dust can be considered as a potential marker of the Anthropocene.Anthropogenic dust signals in stratigraphic records during the past~2000 years differ substantially from those during the early and middle Holocene,which demonstrates that,at least since~2000 years ago,human activity has exceeded the natural forcing of dust transport in northern China.We therefore propose that there are spatial and temporal differences in the onset of the Anthropocene,as defined by anthropogenic dust deposition,which is therefore time-transgressive.Our spectrally-inferred chlorophyll a record is consistent with dust storm activity over the past~2000 years(except since the 1950s),suggesting that anthropogenic dust storms were the dominant control on lake primary production.Prior to the 1950s the interactions of the East Asian summer monsoon(EASM),human activity,dust storms and lake ecosystems resulted in a shift from a pattern in whi

关键词： Anthropocene Stratigraphic marker Dust storms Lake primary production Time-transgressive Great Acceleration

近200年青藏高原东南部真布错硅藻记录与环境变化

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地理学报 2024年第5期79卷 1231-1245页

作者：何晋娜索娜卓嘎张继峰曹鹏熙王俊伟袁艳丽葛梦娟杨凤琴刘建宝太原师范学院地理科学学院晋中030619 西藏自治区生态环境监测中心拉萨850000 西藏大学生态环境学院青藏高原生物多样性与生态环境保护教育部重点实验室拉萨850000 西藏雅尼湿地生态系统国家定位观测研究站拉萨850000 中国科学院青藏高原研究所古生态与人类适应团队北京100101 青藏高原地球系统与资源环境国家重点实验室北京100101

近200年来青藏高原湖泊生态系统对气候变暖的响应研究多集中在深水湖泊,而对大量浅水湖泊生态系统的研究较为匮乏。本文以青藏高原东南部浅水湖真布错为研究对象,通过对沉积物柱芯的^(210)Pb、^(137)Cs测年和高分辨率硅藻鉴定分析,重建... 详细信息

近200年来青藏高原湖泊生态系统对气候变暖的响应研究多集中在深水湖泊,而对大量浅水湖泊生态系统的研究较为匮乏。本文以青藏高原东南部浅水湖真布错为研究对象,通过对沉积物柱芯的^(210)Pb、^(137)Cs测年和高分辨率硅藻鉴定分析,重建该湖过去200年来硅藻属种组合变化,并结合沉积物总有机碳(TOC)含量、总氮(TN)含量、碳氮比(C/N)等指标,探讨湖泊生态系统对气候变化等因素的响应。结果显示,1820—1950年硅藻组成中水生植物附生种Encyonema lange-bertalotii的百分含量较高,表明真布错水生植物较繁盛,湖水透明度高。1950年以来,硅藻组合发生了突变,附生种Encyonema lange-bertalotii的百分含量快速下降,耐低光照的small Fragilaria成为优势属,表明水生植物衰退,湖水透明度降低;同时TOC和TN含量升高,C/N减小,指示湖泊生产力和营养水平升高,藻类在湖泊有机质中占比增加。气温快速升高、降水量增加(冲刷流域更多营养物质进入湖泊)和人类活动增强(流域内出现新建寺庙)可能共同导致湖泊生产力升高,藻类繁盛,水生植物衰退,水体透明度下降,最终引起硅藻群落的突变。因此,在青藏高原气候暖湿化背景下,浅水湖泊可能面临生态系统的转变,未来应该加强该类湖泊的监测与保护。本文记录的高原浅水湖泊生态系统突变时间与中国和全球其他地区基本一致,这也为确定人类世的地层标记提供了新的证据。青藏高原湖泊可以作为研究人类世的天然实验室。

关键词：青藏高原浅水湖泊硅藻古生态气候变化

A novel procedure for pollen-based quantitative paleoclimate reconstructions and its application in China

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Science China Earth Sciences 2017年第11期60卷 2059-2066页

作者： CHEN JianHui LV FeiYa HUANG XiaoZhong H.John B.BIRKS Richard J.TELFORD ZHANG ShengRui XU QingHai ZHAO Yan WANG HaiPeng ZHOU AiFeng HUANG Wei liu jianbao WEI GuoYing Key Laboratory of West China's Environmental System(Ministry of Education) College of Earth and Environmental SciencesLanzhou UniversityLanzhou 730000China Department of Biology and Bjerknes Centre for Climate Research University of BergenN-5020 BergenNorway Institute of Nihewan Archaeology Research Hebei Normal UniversityShijiazhuang 050024China Institute of Geographic Science and Natural Resources Research Chinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China

Traditionally, the evaluation of pollen-based quantitative paleoclimate reconstructions focuses on the ability of calibration sets to infer present climatic conditions and/or the similarity between fossil and modern assemblages. Objective criteria for choosing the most appropriate climate parameter(s) to be reconstructed at a specific site are thus lacking. Using a novel approach for testing the statistical significance of a quantitative reconstruction using random environmental data, in combination with the advantageous large environmental gradients, abundant vegetation types and comprehensive modern pollen databases in China, we describe a new procedure for pollen-based quantitative paleoclimatic reconstructions. First, the most significant environmental variable controlling the fossil pollen assemblage changes is identified. Second, a calibration set to infer changes in this targeted variable is built up, by limiting the modern ranges of other environmental variables. Finally, the pollen-based quantitative reconstruction is obtained and its statistical significance assessed. This novel procedure was used to reconstruct the mean annual precipitation(Pann) from Gonghai Lake in the Lvliang Mountains, and Tianchi Lake in the liupan Mountains, on the eastern and western fringe of the Chinese Loess Plateau, respectively. Both Pann reconstructions are statistically significant(p<0.001), and a sound and stable correlation relationship exists in their common period, showing a rapid precipitation decrease since 3300 cal yr BP. Thus, we propose that this procedure has great potential for reducing the uncertainties associated with pollen-based quantitative paleoclimatic reconstructions in China.

关键词：中国黄土高原古气候重建应用程序花粉基础年平均降水量统计意义定量重建

Carbon budget and balance critical processes of the regional landwater-air interface:Indicating the earth system’s carbon neutrality

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Science China Earth Sciences 2022年第5期65卷 773-782页

作者： Yang GAO Shuoyue WANG Yao LU jianbao liu Sidan LYU Kun SUN Junjie JIA Zhaoxi LI Guirui YU Key Laboratory of Ecosystem Network Observation and Modeling Institute of Geographic Sciences and Natural Resources ResearchChinese Academy of SciencesBeijing 100101China College of Resources and Environment University of Chinese Academy of SciencesBeijing 100049China Key Laboratory of Alpine Ecology Institute of Tibetan Plateau ResearchChinese Academy of SciencesBeijing 100101China

Regional processes on land-water-air interface carbon(C)budget and balance that interconnect the land and sea are in fact C neutrality critical processes within the earth system.It is therefore essential to quantitatively analyze synergistic landwater-air interface C transport and C exchange processes to gain a deep understanding of the important role that terrestrial ecosystems play in“missing C sink”.This paper systematically analyzes global land-water-air interface C migration processes as well as C budget changes and associated impact mechanisms.It also investigates the important role that these C budgets and C cycling processes play in inland water bodies,respective to C budgets at the land-water-air interface.Moreover,this study reveals the regulatory mechanisms of land-water-air interface C budgets and balances under a background of global climate change.It also quantitatively evaluates the status of China’s regional land-sea-air interface C budgets as well as the C sequestration potential of its lake systems.Finally,this study concludes that the explicit quantification of anthropogenic activity impacts on land-water-air interface C transport and exchange processes is of great significance to global C balances and C neutrality.

关键词： C budget C balance C neutrality Critical zone Land-water-air interface exchange Land-sea coordination

Differences in the evolutionary pattern of dust storms over the past 2000 years between eastern and western China and the driving mechanisms

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Science China Earth Sciences 2020年第9期63卷 1422-1424页

作者： Shengqian CHEN jianbao liu Jianhui CHEN Fahu CHEN Key Laboratory of Western China’s Environmental Systems(Ministry of Education) College of Earth and Environmental ScienceLanzhou UniversityLanzhou 730000China Key Laboratory of Alpine Ecology Institute of Tibetan Plateau ResearchChinese Academy of SciencesBeijing 100101China CAS Center for Excellence in Tibetan Plateau Earth Sciences Chinese Academy of SciencesBeijing 100101China

The arid and semi-arid region of East Asia,principally including the deserts in eastern and western China,is the main dust source of the Northern Hemisphere.Dust storm activity in the region has attracted much researc... 详细信息

关键词： storm eastern dust

Reliability of radiocarbon dating on various fractions of loess-soil sequence for Dadiwan section in the western Chinese Loess Plateau

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Frontiers of Earth Science 2014年第4期8卷 540-546页

作者： Zongli WANG Hui ZHAO Guanghui DONG Aifeng ZHOU jianbao liu Dongju ZHANG MOE Key Laboratory of West China's Environmental System Lanzhou University Lanzhou 730000 China Key Laboratory of Desert and Desertification Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou 730000 China

The accurate radiocarbon dating of loess-soil sequences plays an essential role in the reconstruction of the environmental and climatic changes in continental settings during the last glaciation and Holocene. However, our knowledge about the reliability of radiocarbon ages of various fractions of soil and loess samples is still insufficient. Here, we present our study results on radio- carbon ages based on bulk organic matter, humin fraction, and carbonate of samples collected from a loess-paleosol section in the western Chinese Loess Plateau. We compare these observations with the optically stimulated luminescence ages and charcoal radiocarbon ages to evaluate the reliability of these fractions. We observed that the radio- carbon ages of humin fraction are very close to those of charcoal and are consistent with the optically stimulated luminescence ages within the experimental errors. We observed a significant deviation in the radiocarbon ages of carbonate and bulk organic matter from those of charcoal and optically stimulated luminescence ages, likely due to the dilution of these fractions during the pedogenetic process. Our results reveal that, except for charcoal, the humin fraction may yield reliable laC ages for the Chinese loess-soil sequence.

关键词： loess-soil sequence humin fraction charcoal,organic matter radiocarbon dating