Geochemical and grain size analysis on the DQ （Dongqi） profile from Gonghe Basin, northeastern Qinghai-Tibetan Plateau, indi- cates that regional climate has experienced several cold-dry and warm-wet cycles since th...Geochemical and grain size analysis on the DQ （Dongqi） profile from Gonghe Basin, northeastern Qinghai-Tibetan Plateau, indi- cates that regional climate has experienced several cold-dry and warm-wet cycles since the last glacial maximum （LGM）. The cold and dry climate dominated the region before 15.82 cal. ka B.E due to stronger winter monsoon and weaker summer monsoon, but the climate was relatively cold and wetter prior to 21 cal. ka B.E. In 15.824.5 cal. ka B.E, summer monsoon strength in- creased and winter monsoon tended to be weaker, implying an obvious warm climate. Specifically, the relatively cold and dry condition appeared in 14.7-13.7 cal. ka B.E and 12.14.5 cal. ka B.R, respectively, while relatively warm and wet in 13.~12.1 cal. ka B.E. The winter and summer monsoonal strength presents frequent fluctuations in the Holocene and relatively warm and wet conditions emerged in 9.5~.0 cal. ka B.E due to stronger summer monsoon. From 7.0 to 5.1 cal. ka B.E, the cycle of cold-dry and warm-wet climate corresponds to frequent fluctuations of winter and summer monsoons. The climate becomes warm and wet in 5.1 2.7 cal. ka B.E, accompanying increased summer monsoon, but it tends to be cold and dry since 2.7 cal. ka B.R due to en- hanced winter monsoonal strength. In addition, the evolution of regional winter and summer monsoons is coincident with warm and cold records from the polar ice core. In other words, climatic change in the Gonghe Basin can be considered as a regional re- sponse to global climate change.展开更多
Since the Last Glacial Maximum(LGM), the global climate has experienced several stages, such as cold and warming events, which provide an ideal model for evaluating climate change in the future. Based on the pollen re...Since the Last Glacial Maximum(LGM), the global climate has experienced several stages, such as cold and warming events, which provide an ideal model for evaluating climate change in the future. Based on the pollen records in Northeast(NE) China, the vegetation pattern during special periods since the LGM was reconstructed in this work. During the LGM(approximately 18,000 cal yr BP), the steppes expanded rapidly in NE China, and a cold-dry meadow-steppe developed on the Songnen Plain. The Liaohe Plain and the Hulun Buir Plateau were occupied by a steppe-desert, with forest-steppe vegetation grown in the central and southern plains;there were cold-dry coniferous forests and mixed conifer-broadleaf forests in mountainous areas. In the early Holocene(10,000–9,000 cal yr BP), Changbai mountain(CBM) forests thrived in the eastern hilly area and the Sanjiang Plain, while the central region was dominated by steppes, and warm-temperate broadleaf forests developed northward. During the Holocene warm period(approximately 6,000 cal yr BP), CBM forests and cold-temperate coniferous forests developed in the north, while spruce-fir forests developed in the eastern Xiao Hinggan Mountains and the Sanjiang Plain. The distribution centre of deciduous broadleaf forests migrated to the south of the Changbai Mountains and the Liaodong Peninsula. The isolated woodlands increased on the Songnen Plain and the meadow-steppes expanded to the Liaohe Plain. Therefore, the increase in temperature leads to the increase of monsoon precipitation in NE China, which is beneficial to the development of warm-temperate forest vegetation. The increase of summer monsoons and precipitation caused by climate warming may be the main reason for the improved plant load.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 China, however, when the temperature condition was appropriate, an increase in precipitation(especially more spring precipitation) would reduce the competitive advantages of C4 plants. Therefore, the combination of temperature and seasonal precipitation was the important factor that determines the C3/C4 vegetation proportion change in the southern China. Under the premise that the temperature will rise and precipitation will increase in the future, the reduction of a competitive advantage for the C4 plants could affect agricultural production in China.展开更多
The formation and evolution of permafrost in China during the last 20 ka were reconstructed on the basis of large amount of paleo-permafrost remains and paleo-periglacial evidence, as well as paleo-glacial landforms, ...The formation and evolution of permafrost in China during the last 20 ka were reconstructed on the basis of large amount of paleo-permafrost remains and paleo-periglacial evidence, as well as paleo-glacial landforms, paleo-flora and paleofauna records. The results indicate that, during the local Last Glacial Maximum(LLGM) or local Last Permafrost Maximum(LLPMax), the extent of permafrost of China reached 5.3×106-5.4×106 km2, or thrice that of today, but permafrost shrank to only0.80×106-0.85×106 km2, or 50% that of present, during the local Holocene Megathermal Period(LHMP), or the local Last Permafrost Minimum(LLPMin). On the basis of the dating of periglacial remains and their distributive features, the extent of permafrost in China was delineated for the two periods of LLGM(LLPMax) and LHMP(LLPMin), and the evolution of permafrost in China was divided into seven periods as follows:(1) LLGM in Late Pleistocene(ca. 20000 to 13000-10800 a BP)with extensive evidence for the presence of intensive ice-wedge expansion for outlining its LLPMax extent;(2) A period of dramatically changing climate during the early Holocene(10800 to 8500-7000 a BP) when permafrost remained relatively stable but with a general trend of shrinking areal extent;(3) The LHMP in the Mid-Holocene(8500-7000 to 4000-3000 a BP)when permafrost degraded intensively and extensively, and shrank to the LLPMin;(4) Neoglaciation during the late Holocene(4000-3000 to 1000 a BP, when permafrost again expanded;(5) Medieval Warming Period(MWP) in the late Holocene(1000-500 a BP) when permafrost was in a relative decline;(6) Little Ice Age(LIA) in the late Holocene(500-100 a BP), when permafrost relatively expanded, and;(7) Recent warming(during the 20 th century), when permafrost continuously degraded and still is degrading. The paleo-climate, geography and paleopermafrost extents and other features were reconstructed for each of these seven periods.展开更多
通过对共和盆地东部风成沉积的地球化学分析,并结合14C和OSL年代,重建了区域末次盛冰期以来气候变化过程。21 ka BP之前气候寒冷偏湿,21～15.82 ka BP为末次盛冰期(LastGlacial Maximum,LGM),气候极为寒冷干燥;15.82～9.5 ka BP气候转...通过对共和盆地东部风成沉积的地球化学分析,并结合14C和OSL年代,重建了区域末次盛冰期以来气候变化过程。21 ka BP之前气候寒冷偏湿,21～15.82 ka BP为末次盛冰期(LastGlacial Maximum,LGM),气候极为寒冷干燥;15.82～9.5 ka BP气候转暖且偏干,其中14.5～13.6ka BP和11.9～9.5 ka BP气候明显冷干,分别为老仙女木时期(Oldest Dryas,OD)和新仙女木时期(Younger Dryas,YD),而15.82～14.5 ka BP和13.6～11.9 ka BP(BФlling-AllerФd暖期,B/A)相对温暖;9.5～7.2 ka BP暖湿程度明显提高,7.2～5.1 ka BP气候波动频繁,相对冷干和相对暖湿多次更替。5.1～2.7 ka BP暖湿程度基本稳定,之后气候趋于寒冷但湿度明显较大。这些气候变化过程与青藏高原大量的古气候信息记录具有良好的一致性,表明共和盆地气候变化与青藏高原气候变化的高度一致性。展开更多
梭梭属(Haloxylon)植物是藜科的古老孑遗物种,探究末次间冰期(lastinterglacial period,LIG)和末次盛冰期(lastglacial maximum period,LGM)以来中国梭梭属植物的历史地理分布格局及其驱动机制,对了解气候变化背景下旱生植物区系的发展...梭梭属(Haloxylon)植物是藜科的古老孑遗物种,探究末次间冰期(lastinterglacial period,LIG)和末次盛冰期(lastglacial maximum period,LGM)以来中国梭梭属植物的历史地理分布格局及其驱动机制,对了解气候变化背景下旱生植物区系的发展与演化具有重要意义。本研究利用梭梭属85个自然分布点数据(60条梭梭(Haloxylon ammodendron)分布记录、25条白梭梭(H.persicum)分布记录)和2套环境因子数据,整合GIS空间分析和9种物种分布模型,分析了梭梭属末次间冰期以来的地理分布格局变化及其驱动机制。基于62个梭梭属种群的叶绿体基因测序数据,利用最小成本路径方法,模拟了末次间冰期以来梭梭属可能的扩散路径。利用R软件prcomp函数对影响梭梭属分布的环境变量进行主成分分析(principal component analysis,PCA),评价了环境变量对梭梭属适宜分布的贡献,并分析了关键变量与分布适宜性的相关性。结果表明:(1)集成模型的模拟精度较单一模型显著提升,且对白梭梭的模拟精度高于梭梭;(2)末次间冰期以来,梭梭属植物的分布均经历了显著收缩和冰后期扩张,末次间冰期至末次盛冰期时期,在准噶尔盆地、塔里木盆地西部广泛分布的梭梭大面积向西退缩至避难所(准噶尔盆地西北缘和塔里木盆地西北缘);白梭梭从准噶尔盆地、塔里木盆地西端向南退缩至避难所(准噶尔盆地南缘);末次盛冰期至今,梭梭向东沿甘肃北部扩张直至内蒙古西部阿拉善荒漠,白梭梭向东北方向小范围扩张,占据了准噶尔盆地西部和南缘;(3)末次间冰期以来的气候波动对梭梭属植物的分布存在较大限制,降水因子主导了梭梭属适宜分布面积的变化,温度因子影响了梭梭属分布适宜性的高低。展开更多
基金funded by National Natural Science Foundation of China (Nos. 40971005 and 41271215)
文摘Geochemical and grain size analysis on the DQ （Dongqi） profile from Gonghe Basin, northeastern Qinghai-Tibetan Plateau, indi- cates that regional climate has experienced several cold-dry and warm-wet cycles since the last glacial maximum （LGM）. The cold and dry climate dominated the region before 15.82 cal. ka B.E due to stronger winter monsoon and weaker summer monsoon, but the climate was relatively cold and wetter prior to 21 cal. ka B.E. In 15.824.5 cal. ka B.E, summer monsoon strength in- creased and winter monsoon tended to be weaker, implying an obvious warm climate. Specifically, the relatively cold and dry condition appeared in 14.7-13.7 cal. ka B.E and 12.14.5 cal. ka B.R, respectively, while relatively warm and wet in 13.~12.1 cal. ka B.E. The winter and summer monsoonal strength presents frequent fluctuations in the Holocene and relatively warm and wet conditions emerged in 9.5~.0 cal. ka B.E due to stronger summer monsoon. From 7.0 to 5.1 cal. ka B.E, the cycle of cold-dry and warm-wet climate corresponds to frequent fluctuations of winter and summer monsoons. The climate becomes warm and wet in 5.1 2.7 cal. ka B.E, accompanying increased summer monsoon, but it tends to be cold and dry since 2.7 cal. ka B.R due to en- hanced winter monsoonal strength. In addition, the evolution of regional winter and summer monsoons is coincident with warm and cold records from the polar ice core. In other words, climatic change in the Gonghe Basin can be considered as a regional re- sponse to global climate change.
基金supported by the Chinese Academy of Sciences Strategic Priority Research Program (Grant No. XDA01020304)the National Natural Science Foundation of China (Grant Nos. 41730319, 41372175 & 41602361)the National Basic Research Program of China (Grant No. 2015CB953803)
文摘Since the Last Glacial Maximum(LGM), the global climate has experienced several stages, such as cold and warming events, which provide an ideal model for evaluating climate change in the future. Based on the pollen records in Northeast(NE) China, the vegetation pattern during special periods since the LGM was reconstructed in this work. During the LGM(approximately 18,000 cal yr BP), the steppes expanded rapidly in NE China, and a cold-dry meadow-steppe developed on the Songnen Plain. The Liaohe Plain and the Hulun Buir Plateau were occupied by a steppe-desert, with forest-steppe vegetation grown in the central and southern plains;there were cold-dry coniferous forests and mixed conifer-broadleaf forests in mountainous areas. In the early Holocene(10,000–9,000 cal yr BP), Changbai mountain(CBM) forests thrived in the eastern hilly area and the Sanjiang Plain, while the central region was dominated by steppes, and warm-temperate broadleaf forests developed northward. During the Holocene warm period(approximately 6,000 cal yr BP), CBM forests and cold-temperate coniferous forests developed in the north, while spruce-fir forests developed in the eastern Xiao Hinggan Mountains and the Sanjiang Plain. The distribution centre of deciduous broadleaf forests migrated to the south of the Changbai Mountains and the Liaodong Peninsula. The isolated woodlands increased on the Songnen Plain and the meadow-steppes expanded to the Liaohe Plain. Therefore, the increase in temperature leads to the increase of monsoon precipitation in NE China, which is beneficial to the development of warm-temperate forest vegetation. The increase of summer monsoons and precipitation caused by climate warming may be the main reason for the improved plant load.
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 China, however, when the temperature condition was appropriate, an increase in precipitation(especially more spring precipitation) would reduce the competitive advantages of C4 plants. Therefore, the combination of temperature and seasonal precipitation was the important factor that determines the C3/C4 vegetation proportion change in the southern China. Under the premise that the temperature will rise and precipitation will increase in the future, the reduction of a competitive advantage for the C4 plants could affect agricultural production in China.
基金supported by the National Natural Science Foundation of China and Russian Foundation for Basic Research (FRBR) on “Formation, evolution and changes of Pleistocene cryogenic deposits in Eastern Asia” (Grant No. 41811530093)the Key Program of the Department of International Cooperation of the Chinese Academy of Sciences (Assessment of changes in permafrost in China, Russia and Mongolia and their impacts on key engineering infrastructures), (Permafrost extent in China during the Last Glaciation Maximum and Megathermal) of the Strategic Pilot Science and Technology Program of the Chinese Academy of Sciences (Grant No. XDA05120302)the CAS Overseas Professorship of Sergey S. Marchenko, and under the auspices of the International Permafrost Association Working Group on Global Permafrost Extent During the Last Permafrost Maximum (LPM)
文摘The formation and evolution of permafrost in China during the last 20 ka were reconstructed on the basis of large amount of paleo-permafrost remains and paleo-periglacial evidence, as well as paleo-glacial landforms, paleo-flora and paleofauna records. The results indicate that, during the local Last Glacial Maximum(LLGM) or local Last Permafrost Maximum(LLPMax), the extent of permafrost of China reached 5.3×106-5.4×106 km2, or thrice that of today, but permafrost shrank to only0.80×106-0.85×106 km2, or 50% that of present, during the local Holocene Megathermal Period(LHMP), or the local Last Permafrost Minimum(LLPMin). On the basis of the dating of periglacial remains and their distributive features, the extent of permafrost in China was delineated for the two periods of LLGM(LLPMax) and LHMP(LLPMin), and the evolution of permafrost in China was divided into seven periods as follows:(1) LLGM in Late Pleistocene(ca. 20000 to 13000-10800 a BP)with extensive evidence for the presence of intensive ice-wedge expansion for outlining its LLPMax extent;(2) A period of dramatically changing climate during the early Holocene(10800 to 8500-7000 a BP) when permafrost remained relatively stable but with a general trend of shrinking areal extent;(3) The LHMP in the Mid-Holocene(8500-7000 to 4000-3000 a BP)when permafrost degraded intensively and extensively, and shrank to the LLPMin;(4) Neoglaciation during the late Holocene(4000-3000 to 1000 a BP, when permafrost again expanded;(5) Medieval Warming Period(MWP) in the late Holocene(1000-500 a BP) when permafrost was in a relative decline;(6) Little Ice Age(LIA) in the late Holocene(500-100 a BP), when permafrost relatively expanded, and;(7) Recent warming(during the 20 th century), when permafrost continuously degraded and still is degrading. The paleo-climate, geography and paleopermafrost extents and other features were reconstructed for each of these seven periods.
文摘通过对共和盆地东部风成沉积的地球化学分析,并结合14C和OSL年代,重建了区域末次盛冰期以来气候变化过程。21 ka BP之前气候寒冷偏湿,21～15.82 ka BP为末次盛冰期(LastGlacial Maximum,LGM),气候极为寒冷干燥;15.82～9.5 ka BP气候转暖且偏干,其中14.5～13.6ka BP和11.9～9.5 ka BP气候明显冷干,分别为老仙女木时期(Oldest Dryas,OD)和新仙女木时期(Younger Dryas,YD),而15.82～14.5 ka BP和13.6～11.9 ka BP(BФlling-AllerФd暖期,B/A)相对温暖;9.5～7.2 ka BP暖湿程度明显提高,7.2～5.1 ka BP气候波动频繁,相对冷干和相对暖湿多次更替。5.1～2.7 ka BP暖湿程度基本稳定,之后气候趋于寒冷但湿度明显较大。这些气候变化过程与青藏高原大量的古气候信息记录具有良好的一致性,表明共和盆地气候变化与青藏高原气候变化的高度一致性。
