An absolute-dated, bi-decadal-resolution, stalagmite oxygen-isotopic time series from Shigao Cave reveals the evolution of summer monsoon precipitation over the past 9.9 ka BP in northern Guizhou Province, Southwest C...An absolute-dated, bi-decadal-resolution, stalagmite oxygen-isotopic time series from Shigao Cave reveals the evolution of summer monsoon precipitation over the past 9.9 ka BP in northern Guizhou Province, Southwest China. The 18O-inferred climate conditions are divisible into three distinct stages: (1) a maximum humid era from 9.9-6.6 ka BP; (2) a gradual declining precipitation interval between 6.6-1.6 ka BP; and (3) a relatively low precipitation time window after 1.6 ka BP. Consistency of contemporaneous stalagmite Holocene 18O records between Shigao and other caves in the Indian and East Asian monsoon realms support the effect of primary orbital solar forcings on monsoonal precipitation. However, statistical analysis shows a significant spatial asynchroneity of the Holocene Optimum termination in the Asian monsoon territory. The Holocene Optimum ended at 7.2-7.4 ka BP in Oman, located in the Indian monsoon region, and at 5.6-5.8 ka BP in Central China, in the East Asian monsoon zone. In Southwest China, the termination occurred between these periods, at 6.6-7.0 ka BP, and was influenced by both monsoon systems. We propose that this spatially asynchronous ending of Holocene Optimum in Asia may be attributed to sea surface temperature changes in the western tropical Pacific, which is a primary moisture source for the East Asian monsoon.展开更多
Reconstructing the spatial patterns of regional climate and vegetation during specific intervals in the past is important for assessing the possible responses of the ecological environment under future global warming ...Reconstructing the spatial patterns of regional climate and vegetation during specific intervals in the past is important for assessing the possible responses of the ecological environment under future global warming scenarios. In this study, we reconstructed the history of regional vegetation and climate based on six radiocarbon-dated pollen records from the North China Plain. Combining the results with existing pollen records, we reconstruct the paleoenvironment of the North China Plain during the Last Glacial Maximum(LGM) and the Holocene Climatic Optimum(HCO). The results show that changes in the regional vegetation since the LGM were primarily determined by climatic conditions, the geomorphic landscape and by human activity.During the LGM, the climate was cold and dry;mixed broadleaf-coniferous forest and deciduous-evergreen broadleaf forest developed in the southern mountains, and cold-resistant coniferous forest and mixed broadleaf-coniferous forest were present in the northern mountains. The forest cover was relatively low, with mesophytic and hygrophilous meadow occupying the southern part of the plain, and temperate grassland and desert steppe were distributed in the north;Chenopodiaceae-dominated halophytes grew on the exposed continental shelf of the Bohai Sea and Yellow Sea. During the HCO, the climate was warm and wet;deciduous broadleaf forest and deciduous-evergreen broadleaf forest, with subtropical species, developed in the southern mountains, and deciduous broadleaf forest with thermophilic species was present in northern mountains. Although the degree of forest cover was greater than during the LGM, the vegetation of the plain area was still dominated by herbs, while halophytes had migrated inland due to sea level rise. In addition, the expansion of human activities, especially the intensification of cultivation,had a significant influence on the natural vegetation. Our results provide data and a scientific basis for paleoclimate modelling and regional carbon cycle assessment in north China, w展开更多
考古证据揭示在8500~7000 cal.a B. P.左右的全新世大暖期,蒙古高原东部的呼伦贝尔、西辽河上游、阴山东北麓地区曾一度出现过定居化的生活迹象。各地区依托适应于本土环境的经济基础,发展出定居化程度有所差别的社会生活模式。本研究...考古证据揭示在8500~7000 cal.a B. P.左右的全新世大暖期,蒙古高原东部的呼伦贝尔、西辽河上游、阴山东北麓地区曾一度出现过定居化的生活迹象。各地区依托适应于本土环境的经济基础,发展出定居化程度有所差别的社会生活模式。本研究综合分析3个地区代表性遗址的聚落、房址形态、陶器、石器工具组合、动、植物遗存,对其所展现的定居模式、定居程度和定居经济基础进行分析与对比,研究表明呼伦比尔地区定居化生活的经济基础侧重于对多重生态区域内的中小型动物资源的利用,其中水生资源占有较大比重;而西辽河上游和阴山东北麓则采取狩猎采集与原始农业相结合的生业经济,动植物资源利用并重。西辽河上游和阴山东北麓发展出有一定社群规模的村落式定居社会,其中西辽河流域先民的定居化程度高于阴山东北麓和呼伦贝尔地区。全新世大暖期的气候变化,改善了高原地区的水热条件,增强了草原地带的生态多样性,为先民集约化利用栖居地周围的多种动植物资源并在气候条件许可的地带发展农业生产提供了有利契机,对多样性资源的集约利用,奠定了定居化生活的经济基础。但定居化的发展趋势伴随着大暖期的结束而终止,体现出草原地带的史前先民在环境变迁背景下灵活弹性的适应策略。展开更多
The article describes a possible impact of demographic explosion during the Neolith on local ecosystems and on the global climate as well as the role of this explosion in aggravating the course of 4.2 ka cooling event...The article describes a possible impact of demographic explosion during the Neolith on local ecosystems and on the global climate as well as the role of this explosion in aggravating the course of 4.2 ka cooling event. A possible role of human activity in changing the pattern of mid-latitudes westerlies, monsoons and Walker circulation throughout the Holocene is analyzed. It is explained why during the Holocene Climatic Optimum (HCO) monsoons could have been weaker than today, not stronger, as it is commonly stated. It is described how during the HCO the humid Tibetan Plateau could have repelled the Indian monsoon to the west and the East Asian monsoon to the north. The explanation for weaker El Niño-Southern Oscillation (ENSO) during HCO is proposed.展开更多
The response of mangrove ecosystems to the Asian monsoon in the future global warming can be understood by reconstructing the development of mangrove forests during the Holocene climatic optimum（HCO）, using proxies ...The response of mangrove ecosystems to the Asian monsoon in the future global warming can be understood by reconstructing the development of mangrove forests during the Holocene climatic optimum（HCO）, using proxies preserved in coastal sediments. The total organic matter in sediments of a segmented core, with calibrated age ranges between 5.6 and 7.7 cal. ka BP and corresponding to the HCO, from the Qinzhou Bay in Guangxi, China, is quantitatively partitioned into three end-members according to their sources： mangrove-derived, terrigenous,and marine phytoplanktonic, using a three-end-member model depicted by organic carbon isotope（δ13Corg） and the molar ratio of total organic carbon to total nitrogen（C/N）. The percentage of mangrove-derived organic matter（MOM） contribution is used as a proxy for mangrove development. Three visible drops in MOM contribution occurred at ca. 7.3, ca. 6.9, and ca. 6.2 cal. ka BP, respectively, are recognized against a relatively stable and higher MOM contribution level, indicating that three distinct mangrove forest degradations occurred in the Qinzhou Bay during the HCO. The three mangrove forest degradations approximately correspond to the time of the strengthened/weakened Asian winter/summer monsoon. This indicates that even during a period favorable for the mangrove development, such as the HCO, climatic extremes, such as cold and dry events driven by the strengthened/weakened Asian winter/summer monsoon, can trigger the degradation of mangrove forests.展开更多
To date, few research have been reported on the evolution of C3/C4 vegetation in southern China, and the main mechanism influencing the evolution of C3/C4 vegetation is unclear. That makes it difficult for researchers...To date, few research have been reported on the evolution of C3/C4 vegetation in southern China, and the main mechanism influencing the evolution of C3/C4 vegetation is unclear. That makes it difficult for researchers to understand the competition mechanism of C3 and C4 plants under different climate environments and its relationship with the climate factors. It is also not conducive for researchers to assess the influence of future climate change on regional C3/C4 vegetation. Exactly, C3/C4 vegetation change in the regional-scale will have a significant impact on the global carbon cycle and agricultural production.Therefore, it is especially important to reconstruct the evolutionary history of C3/C4 vegetation in southern China and clarify the influencing mechanism of climate change. In this study, we systematically analyzed stable carbon isotope(δ13 C) of the longchain n-alkanes in sediment samples from eight lakes and four peat profiles in southern China, to reconstruct the spatiotemporal evolution of C3/C4 vegetation in these regions since the Last Glacial Maximum(LGM) and to investigate the climate factors that affect the C4 plant abundance change in the research area. The integrated long-chain n-alkane(C27–C33) stable carbon isotope results of samples from Zhanjiang Huguangyan Maar Lake, Xingyun Lake, Lugu Lake and Dingnan peat showed that, from the LGM to the Early Holocene, C4 plant relative abundance exhibited a gradually increasing trend from 21% to 34%. In the Middle Holocene, the C4 plant abundance significantly declined and reached a lowest value of 10%. In space, the C4 plant abundance generally exhibited a gradually declining trend from south to north in the LGM and the Early Holocene, while it showed an opposite trend in the Holocene Climate Optimum(6.0 cal ka BP). It reflected that the main influencing factor on C4 plants spatial distribution was changing from temperature to precipitation. This study indicated that temperature was the dominant factor affecting C4 plant distribution in southern展开更多
基金supported by the National Natural Science Foundation of China (41002061 and 40771009)the Natural Science Foundation of Fujian Province (2010J05093)NSC grants (NSC 99-2611-M-002 -006, 99-2628-M-002-012 to C.-C. S.)
文摘An absolute-dated, bi-decadal-resolution, stalagmite oxygen-isotopic time series from Shigao Cave reveals the evolution of summer monsoon precipitation over the past 9.9 ka BP in northern Guizhou Province, Southwest China. The 18O-inferred climate conditions are divisible into three distinct stages: (1) a maximum humid era from 9.9-6.6 ka BP; (2) a gradual declining precipitation interval between 6.6-1.6 ka BP; and (3) a relatively low precipitation time window after 1.6 ka BP. Consistency of contemporaneous stalagmite Holocene 18O records between Shigao and other caves in the Indian and East Asian monsoon realms support the effect of primary orbital solar forcings on monsoonal precipitation. However, statistical analysis shows a significant spatial asynchroneity of the Holocene Optimum termination in the Asian monsoon territory. The Holocene Optimum ended at 7.2-7.4 ka BP in Oman, located in the Indian monsoon region, and at 5.6-5.8 ka BP in Central China, in the East Asian monsoon zone. In Southwest China, the termination occurred between these periods, at 6.6-7.0 ka BP, and was influenced by both monsoon systems. We propose that this spatially asynchronous ending of Holocene Optimum in Asia may be attributed to sea surface temperature changes in the western tropical Pacific, which is a primary moisture source for the East Asian monsoon.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA05120202)the National Natural Science Foundation of China (Grant Nos. 41702184 & 41630753)+1 种基金the National Key Research and Development Program of China (Grant No. 2017YFA0603403)the Science Foundation of Hebei Normal University (Grant No. L2018B29)
文摘Reconstructing the spatial patterns of regional climate and vegetation during specific intervals in the past is important for assessing the possible responses of the ecological environment under future global warming scenarios. In this study, we reconstructed the history of regional vegetation and climate based on six radiocarbon-dated pollen records from the North China Plain. Combining the results with existing pollen records, we reconstruct the paleoenvironment of the North China Plain during the Last Glacial Maximum(LGM) and the Holocene Climatic Optimum(HCO). The results show that changes in the regional vegetation since the LGM were primarily determined by climatic conditions, the geomorphic landscape and by human activity.During the LGM, the climate was cold and dry;mixed broadleaf-coniferous forest and deciduous-evergreen broadleaf forest developed in the southern mountains, and cold-resistant coniferous forest and mixed broadleaf-coniferous forest were present in the northern mountains. The forest cover was relatively low, with mesophytic and hygrophilous meadow occupying the southern part of the plain, and temperate grassland and desert steppe were distributed in the north;Chenopodiaceae-dominated halophytes grew on the exposed continental shelf of the Bohai Sea and Yellow Sea. During the HCO, the climate was warm and wet;deciduous broadleaf forest and deciduous-evergreen broadleaf forest, with subtropical species, developed in the southern mountains, and deciduous broadleaf forest with thermophilic species was present in northern mountains. Although the degree of forest cover was greater than during the LGM, the vegetation of the plain area was still dominated by herbs, while halophytes had migrated inland due to sea level rise. In addition, the expansion of human activities, especially the intensification of cultivation,had a significant influence on the natural vegetation. Our results provide data and a scientific basis for paleoclimate modelling and regional carbon cycle assessment in north China, w
文摘考古证据揭示在8500~7000 cal.a B. P.左右的全新世大暖期,蒙古高原东部的呼伦贝尔、西辽河上游、阴山东北麓地区曾一度出现过定居化的生活迹象。各地区依托适应于本土环境的经济基础,发展出定居化程度有所差别的社会生活模式。本研究综合分析3个地区代表性遗址的聚落、房址形态、陶器、石器工具组合、动、植物遗存,对其所展现的定居模式、定居程度和定居经济基础进行分析与对比,研究表明呼伦比尔地区定居化生活的经济基础侧重于对多重生态区域内的中小型动物资源的利用,其中水生资源占有较大比重;而西辽河上游和阴山东北麓则采取狩猎采集与原始农业相结合的生业经济,动植物资源利用并重。西辽河上游和阴山东北麓发展出有一定社群规模的村落式定居社会,其中西辽河流域先民的定居化程度高于阴山东北麓和呼伦贝尔地区。全新世大暖期的气候变化,改善了高原地区的水热条件,增强了草原地带的生态多样性,为先民集约化利用栖居地周围的多种动植物资源并在气候条件许可的地带发展农业生产提供了有利契机,对多样性资源的集约利用,奠定了定居化生活的经济基础。但定居化的发展趋势伴随着大暖期的结束而终止,体现出草原地带的史前先民在环境变迁背景下灵活弹性的适应策略。
文摘The article describes a possible impact of demographic explosion during the Neolith on local ecosystems and on the global climate as well as the role of this explosion in aggravating the course of 4.2 ka cooling event. A possible role of human activity in changing the pattern of mid-latitudes westerlies, monsoons and Walker circulation throughout the Holocene is analyzed. It is explained why during the Holocene Climatic Optimum (HCO) monsoons could have been weaker than today, not stronger, as it is commonly stated. It is described how during the HCO the humid Tibetan Plateau could have repelled the Indian monsoon to the west and the East Asian monsoon to the north. The explanation for weaker El Niño-Southern Oscillation (ENSO) during HCO is proposed.
基金The National Basic Research Program (973 Program) of China under contract No.2010CB951203the National Natural Science Foundation of China under contract Nos 41376075,41576061 and 41206057
文摘The response of mangrove ecosystems to the Asian monsoon in the future global warming can be understood by reconstructing the development of mangrove forests during the Holocene climatic optimum（HCO）, using proxies preserved in coastal sediments. The total organic matter in sediments of a segmented core, with calibrated age ranges between 5.6 and 7.7 cal. ka BP and corresponding to the HCO, from the Qinzhou Bay in Guangxi, China, is quantitatively partitioned into three end-members according to their sources： mangrove-derived, terrigenous,and marine phytoplanktonic, using a three-end-member model depicted by organic carbon isotope（δ13Corg） and the molar ratio of total organic carbon to total nitrogen（C/N）. The percentage of mangrove-derived organic matter（MOM） contribution is used as a proxy for mangrove development. Three visible drops in MOM contribution occurred at ca. 7.3, ca. 6.9, and ca. 6.2 cal. ka BP, respectively, are recognized against a relatively stable and higher MOM contribution level, indicating that three distinct mangrove forest degradations occurred in the Qinzhou Bay during the HCO. The three mangrove forest degradations approximately correspond to the time of the strengthened/weakened Asian winter/summer monsoon. This indicates that even during a period favorable for the mangrove development, such as the HCO, climatic extremes, such as cold and dry events driven by the strengthened/weakened Asian winter/summer monsoon, can trigger the degradation of mangrove forests.
基金supported by the “Strategic Priority Research Program” of the Chinese Academy of Sciences (Grant No. XDA05120103)the National Natural Science Foundation of China (Grant Nos. 41603013 & 41572163)
文摘To date, few research have been reported on the evolution of C3/C4 vegetation in southern China, and the main mechanism influencing the evolution of C3/C4 vegetation is unclear. That makes it difficult for researchers to understand the competition mechanism of C3 and C4 plants under different climate environments and its relationship with the climate factors. It is also not conducive for researchers to assess the influence of future climate change on regional C3/C4 vegetation. Exactly, C3/C4 vegetation change in the regional-scale will have a significant impact on the global carbon cycle and agricultural production.Therefore, it is especially important to reconstruct the evolutionary history of C3/C4 vegetation in southern China and clarify the influencing mechanism of climate change. In this study, we systematically analyzed stable carbon isotope(δ13 C) of the longchain n-alkanes in sediment samples from eight lakes and four peat profiles in southern China, to reconstruct the spatiotemporal evolution of C3/C4 vegetation in these regions since the Last Glacial Maximum(LGM) and to investigate the climate factors that affect the C4 plant abundance change in the research area. The integrated long-chain n-alkane(C27–C33) stable carbon isotope results of samples from Zhanjiang Huguangyan Maar Lake, Xingyun Lake, Lugu Lake and Dingnan peat showed that, from the LGM to the Early Holocene, C4 plant relative abundance exhibited a gradually increasing trend from 21% to 34%. In the Middle Holocene, the C4 plant abundance significantly declined and reached a lowest value of 10%. In space, the C4 plant abundance generally exhibited a gradually declining trend from south to north in the LGM and the Early Holocene, while it showed an opposite trend in the Holocene Climate Optimum(6.0 cal ka BP). It reflected that the main influencing factor on C4 plants spatial distribution was changing from temperature to precipitation. This study indicated that temperature was the dominant factor affecting C4 plant distribution in southern
