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泸沽湖是云贵高原第二大深水湖。取自水深44.5m处长度880cm的连续岩芯显示,泸沽湖沉积岩芯物理特征变化不明显,色调单一、物质构成均匀、植物残体(古树叶)丰富。本文对该岩芯上部474cm进行了孢粉分析和TOC(总有机碳)、CaCO_3(碳酸钙)百分含量的测定。在16个树叶残体AMS~(14)C测年基础上建立了岩芯的年代序列。岩芯孢粉组合表明,在泸沽湖流域,15000~12300a B.P.植被以松林为主,伴有山地针叶阔叶混交林,指示温凉偏湿的气候条件;12300~10300a B.P.的植被以松林减少而落叶阔叶林扩张为特点,表明当时气候相对偏暖偏干;在早全新世(10300~7500a B.P.)和中全新世(7500~3800a B.P.),植被以松林占优势,伴有铁杉林和云冷杉林,植被盖度大,反映温暖湿润的气候条件;在中全新世常绿栎类偏多,表明有效湿度不如早全新世;在3800~3300a B.P.,松林明显减少而硬叶常绿栎林急剧扩张,指示了一次持续的冷干事件;在晚全新世(3300a B.P.至今),松林有所恢复但未达到早中全新世的水平,常绿青冈林增加并出现较多的铁杉林和云杉林,但植被盖度明显降低,表明晚全新世的气温和湿度比早中全新世均偏低。TOC和CaCO_3含量反映的湖泊环境和湖面变化与孢粉分析结果有较好的对应,虽然彼此在年代上存在一定的差异。碳酸盐含量变化显示在13600~3400a B.P.期间湖水整体较高并形成间断性外流湖。泸沽湖沉积记录不仅揭示了末次冰消期以来升温-高温-降温的变化趋势,还记录了与Younger Dryas(YD)和约4000a B.P.的冷事件等相关的气候异常事件。因此,本研究对于认识我国西南地区现代气候环境变化过程、气候突变事件及植被演化具有重要意义。
Lugu Lake is the second largest deep lake in the Yunnan-Guizhou Plateau. The continuous core taken from the depth of 44.5m and the length of 880cm shows that the physical characteristics of the sedimentary core in Lugu Lake are not obviously changed, the color tone is single, the material composition is even, and the plant residues (ancient foliage) are rich. In this paper, the sporopollen analysis and TOC (total organic carbon), CaCO_3 (calcium carbonate) percentage of 474 cm above the core were measured. The chronology of core was established on the basis of 16 tree-leaf AMS ~ (14) C dating. The core sporopollen assemblage shows that in the Lugu Lake basin, the 15,000-12,300 BPM vegetation is mainly dominated by pine forests, accompanied by the mountain coniferous and broad-leaved mixed forests, indicating the climatic conditions of warm and humid climate. The vegetation of 12300 ~ 10300 BPM is reduced by pine forests While the deciduous broad-leaved forest was expanded, indicating that the climate was relatively warm and dry at the time. In the early Holocene (10300-7500 a BP) and Middle Holocene (7500-3800 a BP), the vegetation was dominated by pine forests with hemlock and Spruce forest, vegetation coverage is large, reflecting the warm and humid climatic conditions; in the Mid-Holocene oak, more effective than the Early Holocene; in 3800 ~ 3300a BP, pine significantly reduced while the hard-leaf evergreen oak The rapid expansion of Lin indicated a continuous cold and dry episode. In the late Holocene (since the 3300a BP up to now), the pine forests recovered but did not reach the level of the Early Mid-Holocene. The evergreen glauca forest increased and there were more hemlock forests and Spruce forest, but the vegetation coverage decreased significantly, indicating that the late Holocene temperature and humidity than the early mid-Holocene are low. The changes of lake environment and lake surface reflected by TOC and CaCO_3 content are in good agreement with the results of sporopollen analysis, although there are some differences in the ages. Changes in carbonate content show that during the period of 13600 to 3400a B.P., the lakes were generally high and formed intermittent outflow lakes. The sedimentary record of Lugu Lake not only reveals the trend of temperature rise-high temperature-temperature decrease since the last ice-depletion period, but also records the climatic anomalies related to the Younger Dryas (YD) and cold events of about 4000a B.P. Therefore, this study is of great significance for understanding the process of climate change, climate abrupt change and vegetation evolution in Southwest China.