【作者】 赵得爱； 吴海斌； 吴建育； 郭正堂；

【Author】 Zhao De’ai~(①②) Wu Haibin~①Wu Jianyu~(①②) Guo Zhengtang~①(①Key laboratory of Cenozoic Geology and Environment,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029;②University of Chinese Academy of Sciences,Beijing 100049)

【机构】 中国科学院地质与地球物理研究所新生代地质与环境重点实验室； 中国科学院大学；

【摘要】 过去典型增温时段的自然植被演化规律是未来增温情形下植被变化趋势的重要参照。黄土高原全新世中期（4～8kaB.P.）和末次间冰期（80～110kaB.P.）温度分别比现高约1.2℃和2～5℃,是揭示过去不同增温幅度下植被演化的理想时段。通过对黄土高原东西部黄土一古土壤序列有机碳同位素(δ¹³C_org)对比研究表明:在全新世中期黄土高原东西部有机碳同位素变化一致,相对末次盛冰期表现为正偏2.2‰～2.9‰,指示C₄植物丰度增加。而在末次间冰期黄土高原东、西部不同地貌单元有机碳同位素结果产生空间分异,相对末次盛冰期西部梁峁区表现为负偏约0.8‰,指示C₄植物丰度减少,而东部塬区则表现为正偏0.9‰～4.0‰,指示C₄植物丰度增加。由于上述典型时段大气CO₂浓度相近且温度升高,末次间冰期与全新世中期黄土高原C₄植物丰度变化的差异可能与降水增加的季节性变化有关。上述结果表明,在过去典型增温期不同增温幅度下黄土高原东、西部不同地貌单元植被演化呈现明显不同。更多还原

【Abstract】 The characteristics of the natural vegetation evolution during typical warming periods in the past reconstructed by organic carbon isotope may not only attribute to understand the driving mechanism during past climate change, but also improve knowledge for predicting plants’ evolution in the future.The temperature of Loess Plateau during the Middle Holocene（4～8kaB.P.） and the Last Interglacial（80～HOkaB.P.） is 1.2°C and 2～5°C higher than present,respectively.These two periods are ideal analogues to discuss the possible vegetation evolution trend within different warming magnitude.We systematically collected the data of organic carbon isotope composition from Luochuan（35°47’N,109°26’E）,Xunyi（35°14’N,108°24’E）,and Lantian（34°12 ’N,109°12 ’E）,and Yuanbu （35°38’N,103°09’E） loess-paleosol sequences,and added a new Zhouzhuang-Zhangwan section on the west of Loess Plateau to better understand the palaeovegetation evolution for the whole Loess Plateau.Zhouzhuang section （35°02’N,105°28’E） is located in the northeastern part of Tianshui City,while Zhangwan section （34°41’N,105°45’E ） is 46km away on the southeast direction of Zhouzhuang.The top part of the two sections was disturbed by modern agricultural activities.The Holocene paleosol layer of Zhangwan section was entirely eroded. We systematically collected the samples of Zhouzhuang section from S₀ to L₁ and Zhangwan section from L₁ to S₁ at 2cm intervals in the upper 4 meters and 5cm intervals below.In order to obtain a complete section since the Last Interglacial,we connected the two sections through magnetic susceptibility indoor.Forδ¹³C_org,samples were measured by Picarro CM-CRDS.The results of standard materials（n = 12 ） demonstrated that the standard deviation of the instrumental measurement is≤±0.2‰（V-PDB）. In the east part of CLP,theδ¹³C values are more positive than present and can be reached as much as—17.1‰in the southeast and -20.4‰in the northeast during the Last Interglacial.The values of the Middle Holocene are more positive than present and even Last Interglacial.The values of the western part also show similar trend with the east during the Middle Holocene and can be reached -20.9‰.However,during the Last Interglacial period,theδ¹³C_org values of the west part of CLP are more negative than present,and values can reach -24.8‰, which is even more negative than the Last Glacial,opposing trends to the changes in the east region.The organic carbon isotopes of both east and west Loess Plateau show consistent variation tendency with positive amplitude of 2.2‰～2.9‰comparing to the Last Glacial Maximum（LGM）,indicating the increase of the biomass of C₄ grass. However,it shows a different variation in the east and west during the Last Interglacial.The eastern and western tablelands show a positive tendency while the east part shows a positive value of 0.9‰～4.0‰,indicating the increase of the C₄ grass.In the western loess hill,the data shows a negative value of 0.8‰,which indicating the decrease of C₄ plants.As these two periods have similar atmospheric CO₂ concentration and the temperature had increased,the differences of the biomass of C₄ vegetation between east and west can be attribute to the increasing of precipitation and seasonality.This study shows the evolution of vegetation is significantly distinct in the eastern and western Loess Plateau under different warming amplitudes. In this context,we took these two periods as analogues for the warming future.Regardless of the effects of atmospheric CO₂ concentration changes and human activities,the biomass of C₄ grasses in the eastern and western tablelands of Loess Plateau would increase along with global warming;in the western loess hill,a trend of first increase then decrease would occur.更多还原