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Biome reconstruction on the Tibetan Plateau since the Last Glacial Maximum using a machine learning method

Science China Earth Sciences 2022年第3期65卷 518-535页

作者： Feng QIN Yan ZHAO xianyong cao Key Laboratory ofLand Surface Pattern and Simulation Institute of Geographic Sciences and Natural Resources ResearchChinese Academy of SciencesBeijing 100101China Alpine Paleoecology and Human Adaptation(ALPHA)Group State Key Laboratory of Tibetan Plateau Earth System Science(LATPES)Institute of Tibetan Plateau ResearchChinese Academy of SciencesBeijing 100101China University of Chinese Academy of Sciences Beijing 100049China

Historical biome changes on the Tibetan Plateau provide important information that improves our understanding of the alpine vegetation responses to climate ***,a comprehensively quantitative reconstruction of the historical Tibetan Plateau biomes is not possible due to the lack of quantitative methods that enable appropriate classification of alpine biomes based on proxy data such as fossil pollen *** this study,a pollen-based biome classification model was developed by applying a random forest algorithm(a supervised machine learning method)based on modern pollen assemblages on and around the Tibetan Plateau,and its robustness was assessed by comparing its results with the predictions of the biomisation *** results indicated that modern biome distributions reconstructed using the random forest model based on modern pollen data generally concurred with the observed zonal *** random forest model had a significantly higher accuracy than the biomisation method,indicating the former is a more suitable tool for reconstructing alpine biome changes on the Tibetan *** random forest model was then applied to reconstruct the Tibetan Plateau biome changes from 22 ka BP to the present based on 51 fossil pollen *** reconstructed biome distribution changes on the Tibetan Plateau generally corresponded to global climate changes and Asian monsoon *** the Last Glacial Maximum,the Tibetan Plateau was mainly desert with subtropical forests distributed in the *** the last deglaciation,the alpine steppe began expanding and gradually became zonal vegetation in the central and eastern *** meadow occupied the eastern and southeastern areas of the Tibetan Plateau since the early Holocene,and the forest-meadow-steppe-desert pattern running southeast to northwest on the Tibetan Plateau was established *** the mid-Holocene,subtropical forests extended north,which reflected the“optimum”***

关键词： Biome reconstruction Random forest algorithm Biomisation method Pollen data Last Glacial Maximum Tibetan Plateau

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Improving the quality of pollen-climate calibration-sets is the primary step for ensuring reliable climate reconstructions

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Science Bulletin 2018年第20期63卷 1317-1318页

作者： xianyong cao Fang Tian Wei Ding Key Laboratory of Alpine Ecology and Biogeography Institute of Tibetan Plateau Research Chinese Academy of Sciences Beijing Key Laboratory of Resource Environment and GIS College of Resource Environment and Tourism Capital Normal University Institute of Geological Sciences Palaeontology Free University of Berlin

Pollen-based climate reconstructions have been widely applied in China [1,2]as an essential way to investigate quantitatively past climate change,which is necessary to improve the reliability of future climate predictions [3].However,their usefulness is often doubted,particularly for those regions with a long history of civilization (*** China),where both the modern and past vegetation are heavily disturbed by human activities [4-6].Which factors influence the integrity of pollen-based climate reconstructions and how to improve their reliability are rigorous challenges for *** work focusing on these two questions has used modern pollen data from China or eastern continental Asia and mainly concludes that past climate reconstruction is quite sensitive to the clualitv of the calibration-set [2,7].

关键词： pollen-climate

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A Cool-Arid Climate with Large Temperature Seasonality Implied by Arboreal Pollen in the Early Holocene,North-Central China

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Journal of Earth Science 2023年第5期34卷 1629-1631页

作者： Fang Tian Meijiao Chen Qinghai Xu xianyong cao College of Resource Environment and Tourism Capital Normal UniversityBeijing 100048China College of Geography Sciences Hebei Normal UniversityShijiazhuang 050024China Group of Alpine Paleoecology and Human Adaptation(ALPHA) State Key Laboratory of Tibetan Plateau Earth SystemEnvironment and Resources(TPESER)Institute of Tibetan Plateau ResearchChinese Academy of SciencesBeijing 100101China

The climate of the North-Central China during the Early Holocene is still debated,particularly with regard to precipitation,despite various paleoclimate records based on multi proxies and models(Chen et al.,2015;Liu J B et al.,2015;Liu Z Y et al.,2014).The temperature pattern is also uncertain because of a lack of temperature records for north-central *** sequences are still the most abundant paleo-environmental record particularly for north-central China and have the potential to explore the past precipitation and temperature changes,because both precipitation and temperature are essential for plant growth,and the sensitivity to climatic variables varies among different plants(Liang et al.,2020).Quantitative climate reconstructions based on the modern pollen-climate relationship have been widely generated for east Asia,and the results used to explore the spatial-temporal patterns and mechanisms of past climate changes(Chen et al.,2020,2015;Herzschuh et al.,2019).

关键词： China Holocene climate

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Complementarity of lacustrine pollen and sedimentary DNA in representing vegetation on the central-eastern Tibetan Plateau

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Frontiers of Earth Science 2023年第4期17卷 1037-1048页

作者： Fang TIAN Meijiao CHEN Weihan JIA Ulrike HERZSCHUH xianyong cao College of Resource Environment and Tourism Capital Normal UniversityBeijing 100048China Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research Polar Terrestrial Environmental Systems Research GroupPotsdam 14473Germany University of Potsdam Institute of Environmental Science and GeographyPotsdam 14476Germany University of Potsdam Institute of Biochemistry and BiologyPotsdam 14476Germany Group of Alpine Paleoecology and Human Adaptation(ALPHA) State Key Laboratory of Tibetan Plateau Earth SystemEnvironment and Resources(TPESER)Institute of Tibetan Plateau ResearchChinese Academy of SciencesBeijing 100101China

Plant environmental DNA extracted from lacustrine sediments(sedimentary DNA,sedDNA)has been increasingly used to investigate past vegetation changes and human impacts at a high taxonomic ***,the representation of vegetation communities surrounding the lake is still *** this study,we compared plant sedDNA metabarcoding and pollen assemblages from 27 lake surface-sediment samples collected from alpine meadow on the central-eastern Tibetan Plateau to investigate the representation of sedDNA *** general,the identified components of sedDNA are consistent with the counted pollen taxa and local plant *** to pollen identification,sedDNA data have higher taxonomic resolution,thus providing a potential approach for reconstructing past plant *** sedDNA signal is strongly influenced by local plants while rarely affected by exogenous *** of the overrepresentation of local plants and PCR bias,the abundance of sedDNA sequence types is very variable among sites,and should be treated with caution when investigating past vegetation cover and climate based on sedDNA *** finding suggests that sedDNA analysis can be a complementary approach for investigating the presence/absence of past plants and history of human land-use with higher taxonomic resolution.

关键词： Tibetan Plateau plant DNA metabarcoding pollen lake sediment plant diversity vegetation history

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Holocene climate changes and paleoecology on the Tibetan Plateau:recent advances

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Frontiers of Earth Science 2023年第4期17卷 899-904页

作者： Juzhi HOU xianyong cao Duo WU Mingda WANG Group of Alpine Paleoecology and Human Adaptation State Key Laboratory of Tibetan Earth SystemResources and EnvironmentInstitute of Tibetan Plateau ResearchChinese Academy of SciencesBeijing 100101China MOE Key Laboratory of Western China’s Environmental Systems College of Earth and Environmental SciencesLanzhou UniversityLanzhou 730000China School of Geographical Sciences Liaoning Normal UniversityDalian 116029China

*** Tibetan Plateau(TP)is the largest and highest terrain on the Earth,comprising more than 80%of continents higher than 4000 m above sea *** extremely high elevation resulted in cold and arid climate,sparse vegetation,limited available water resources,thin oxygen on TP,as well as desolated landscape,which makes it one of the most unfriendly habitable places on the ***,ancient humans lived on TP as early as 200 thousand years ago(Chen et al.,2019;Zhang et al.,2020),and developed ancient civilizations,including the Tibetan Empire,Guge Kingdom in historical periods.

关键词： Tibetan Plateau landscape

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Cloning and expression of swine myostatin gene and its application in animal immunization trial

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Science China(Life Sciences) 2005年第4期48卷 368-374页

作者： MA xianyong cao Yongchang SHU Dingming BI Yingzuo Genetic Engineering Laboratory College of Animal Science South China Agricultural University Guangzhou 510642 China Genetic Engineering Laboratory College of Animal Science South China Agricultural University Guangzhou 510642 China Genetic Engineering Laboratory College of Animal Science South China Agricultural University Guangzhou 510642 China Genetic Engineering Laboratory College of Animal Science South China Agricultural University Guangzhou 510642 China

We have amplified swine myostatin (MSTN) gene by reverse transcription poly-merase chain reaction (RT-PCR) and cloned it into pGEM-T Easy vector. The cloned swine MSTN gene consists of 1128 nucleotides, which has been submitted to GenBank (acquired reg-istered code- AY448008). The cloned swine MSTN gene was successfully expressed in E. coli without the first 25 amino acids. Crude extraction of the expressed recombinant MSTN protein was used to immunize mice to investigate the effects on their bodyweights. We show here that the body weights of the immunized mice were higher than that of the controls, even though the difference was not significant. Surprisingly, the progenies of the immunized mice also were heavier than the controls. Especially at day 3, the average body weight of the immunized mice was 10.5% higher than that of the controls , which is significant (p < 0.05).

关键词： myostatin, gene cloning, sequencing, protein expression, detection, immunization.

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Spatial distribution of charcoal in topsoil and its potential determinants on the Tibetan Plateau

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Frontiers of Earth Science 2023年第4期17卷 1059-1069页

作者： Yixuan WANG Chaoqun cao Yanrong ZHANG Lina LIU Nannan WANG Wenjia LI xianyong cao Alpine Paleoecology and Human Adaptation Group(ALPHA) State Key Laboratory of Tibetan Plateau Earth SystemEnvironment and Resources(TPESER)Institute of Tibetan Plateau ResearchChinese Academy of SciencesBeijing 100101China University of the Chinese Academy of Sciences Beijing 100049China College of Life Sciences Zhejiang Normal UniversityJinhua 321004China

As an important proxy for investigating past fire activities,charcoal is often used to explore the characteristics of fire distribution and its relationships with vegetation,climate,and human *** into the spatial distribution and environmental determinants for charcoal,however,is still *** this study,we identified and counted charcoal from topsoil samples covering the Tibetan Plateau using the pollen methodology,and investigated its relationships with vegetation net primary production(NPP),elevation,climate(precipitation,mean temperature of the coldest month and warmest month)and human population by boosted regression trees(BRT).Results reveal that the concentration of microscopic charcoal,macroscopic charcoal,and total charcoal all increase from south-west to north-east,which is consistent with the trend that the population density on the Tibetan Plateau is high in the east and low in the west,suggesting that an increase in human activity is likely to promote the occurrence of *** BRT modeling reveals that NPP,elevation,and mean temperature of the coldest month are important factors for total charcoal concentration on the Tibetan Plateau,and the frequency and intensity of fires further increase with increasing vegetation biomass,decreasing elevation,and decreasing mean temperature of the coldest *** spatial variation characteristics of charcoal from topsoil on the Tibetan Plateau not only reflect well the spatial fire situation in the region,but also have a good indicative significance for vegetation,climate,and human activities.

关键词： BRT charcoal fire regime climate vegetation human activities

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Abrupt vegetation shifts caused by gradual climate changes in central Asia during the Holocene

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Science China Earth Sciences 2017年第7期60卷 1317-1327页

作者： ZHAO Yan LIU YaoLiang GUO ZhengTang FANG KeYan LI Quan cao xianyong Institute of Geographic Sciences and Natural Resources Research Chinese Academy of Sciences Beijing 100101 China University of Chinese Academy of Sciences Beijing 100049 China Key Laboratory of Cenozoic Geology and Environment Institute of Geology and Geophysics Chinese Academy of Sciences Beijing 100029 China Chinese Academy of Sciences Center for Excellence in Tibetan Plateau Earth Sciences Beijing 100101 China College of Geographical Sciences Fujian Normal University Fuzhou 350007 China Alfred Wegener Institute Helmholtz Center for Polar and Marine Research 14473 Potsdam Germany

Understanding the response of ecosystems to past climate is critical for evaluating the impacts of future climate changes.A large-scale abrupt shift of vegetation in response to the Holocene gradual climate changes has been well documented for the Sahara-Sahel ecosystem. Whether such a non-linear response is of universal significance remains to be further addressed. Here,we examine the vegetation-climate relationships in central Asia based on a compilation of 38 high-quality pollen records. The results show that the Holocene vegetation experienced two major abrupt shifts, one in the early Holocene(Shift I, establishing shift) and another in the late Holocene(Shift II, collapsing shift), while the mid-Holocene vegetation remained rather stable. The timings of these shifts in different regions are asynchronous, which are not readily linkable with any known abrupt climate shifts,but are highly correlated with the local rainfalls. These new findings suggest that the observed vegetation shifts are attributable to the threshold effects of the orbital-induced gradual climate changes. During the early Holocene, the orbital-induced precipitation increase would have first reached the threshold for vegetation "establishment" for moister areas, but significantly later for drier areas. In contrast, the orbital-induced precipitation decrease during the late Holocene would have first reached the threshold, and led to the vegetation "collapse" for drier areas, but delayed for moister areas. The well-known 4.2 kyr BP drought event and human intervention would have also helped the vegetation collapses at some sites. These interpretations are strongly supported by our surface pollen-climate analyses and ecosystem simulations. These results also imply that future climate changes may cause abrupt changes in the dry ecosystem once the threshold is reached.

关键词： Fossil pollen Vegetation response Threshold effects Holocene climate Central Asia

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Hydrological Variations and the Ancient Silk Road in the Northern Tarim Basin between Han and Sui Dynasties

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Acta Geologica Sinica(English Edition) 2020年第3期94卷 646-657页

作者： Lü Fenglin ZHANG Hua HOU Juzhi cao xianyong LIU Chenglin Institute of Mineral Resources Chinese Academy of Geological SciencesBeijing 100037China 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 fluctuation pattern of China’s civilization can be ascribed to climate change and historical geopolitical variations. The ancient Silk Road served as the most prosperous route connecting East Asia and Europe during Han Dynasty(206 BC–220 AD) and Sui-Tang Dynasties(581–907 AD), but was deserted in Wei, Jin, Northern and Southern dynasties(220–580 AD), of which the Tarim Basin was a key area. However, our understanding about the decline of the route during this period remains limited. Here, we present an ~7-year resolution record based on optically stimulated luminescence(OSL) age-depth model(ca. 120 BC–750 AD) from Luntai(LT) profile, about 5 km from the modern Tarim River, which fed the ancient oases, to assess the potential causes on the documented decline of the ancient Silk Road between Late Han and Sui dynasties. In this study, five episodes of hydrological change were identified by combining grain size, magnetic susceptibility, geochemistry and TOC/TN contents. Our reconstruction reveals that cold and wet climate dominated at 120 BC–50 AD and 550–750 AD, respectively, indicated by strong hydrodynamic conditions. Relatively warm and humid climate occurred at 120–550 AD, between Eastern Han and Sui-Tang dynasties, indicating a better and more suitable local environment. A comparison between the studied region and other areas of China demonstrates that the paleoclimatic variations in eastern and western China exhibit rough discrepancies, and the hydrological conditions in arid region is inconsistent with the decline of ancient Silk Road in the northern Tarim Basin. We suggest that political and societal factors are the key issues that caused the interruption of Silk Road during Wei, Jin, Northern and Southern dynasties, such as the co-occurrence of societal crises, turmoil and division in eastern China, rather than the deteriorating climatic condition in the northern Tarim basin.

关键词： hydrological changes paleochannel paleoclimate climate change Silk Road

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Vegetation stability during the last two centuries on the western Tibetan Plateau:a palynological evidence

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Frontiers of Earth Science 2023年第4期17卷 1049-1058页

作者： Yanrong ZHANG Nannan WANG Lina LIU Mingda WANG Xiaoshan YU xianyong cao Alpine Paleoecology and Human Adaptation Group(ALPHA) State Key Laboratory of Tibetan Plateau Earth SystemEnvironment and Resources(TPESER)Institute of Tibetan Plateau ResearchChinese Academy of SciencesBeijing 100101China University of Chinese Academy of Science Beijing 100049China School of Geography Liaoning Normal UniversityDalian 116029China

Investigating the dynamics of vegetation is an essential basis to know how to protect ecological environments and to help predict any changes in *** of its fragile alpine ecosystem,the Tibetan Plateau is a particularly suitable area for studying vegetation changes and their driving *** this study,we present a high-resolution pollen record covering the last two centuries extracted from Gongzhu Co on the western Tibetan *** steppe is the predominant vegetation type in the surrounding area throughout the past 250 years with stable vegetation composition and abundance,as revealed by pollen spectra dominated by Artemisia,Ranunculaceae,Cyperaceae,and *** canonical correspondence analysis(DCCA)of the pollen data reveals low turnover in compositional species(0.41 SD),suggesting that the vegetation in the Gongzhu catchment had no significant temporal change,despite climate change and population increases in recent *** additionally ran DCCA on ten other pollen records from the Tibetan Plateau with high temporal resolution(1-20 years)covering recent centuries,and the results also show that compositional species turnover(0.15-0.81 SD)is relatively low,suggesting that the vegetation stability may have prevailed across the Tibetan Plateau during recent *** high-resolution pollen records and high taxonomic-resolution palaeo-vegetation records(such as sedaDNA),however,are needed to confirm the vegetation stability on the Tibetan Plateau.

关键词： pollen compositional 1species turnover vegetation change ecological stability

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