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引用本文:杨春和,杨欢,郑平波,段立曾,张晓楠,张虎才,沈才明,孙惠玲.抚仙湖沉积物多指标记录的过去5000年湖泊环境变化.湖泊科学,2022,34(4):1359-1371. DOI:10.18307/2022.0426
Yang Chunhe,Yang Huan,Zheng Pingbo,Duan Lizeng,Zhang Xiaonan,Zhang Hucai,Shen Caiming,Sun Huiling.Lake environmental changes over the past 5000 years recorded by multiple proxies of sediments in Lake Fuxian, southwest China. J. Lake Sci.2022,34(4):1359-1371. DOI:10.18307/2022.0426
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抚仙湖沉积物多指标记录的过去5000年湖泊环境变化
杨春和1, 杨欢2, 郑平波1, 段立曾3, 张晓楠3, 张虎才3, 沈才明1, 孙惠玲1
1.云南师范大学地理学部, 云南省高原地理过程与环境变化重点实验室, 昆明 650500;2.中国地质大学(武汉)地理与信息工程学院, 流域关键带演化湖北省重点实验室, 武汉 430074;3.云南大学资源环境与地球科学学院, 高原湖泊生态与污染治理研究院, 昆明 650504
摘要:
我国西南地区湖泊众多,利用湖泊沉积物已开展了大量全新世植被、降水、温度和水位等的重建工作.然而,代用指标的季节性差异和气候演变的区域差异使得不同代用指标和地区重建的古气候结果存在较大差异,需要更多可靠记录来相互佐证和构建我国西南地区气候变化的详细图景.本文以云南抚仙湖FXH-6钻孔沉积物为研究对象,对正构烷烃和色度指标作了分析,在厘清其来源及环境指示意义的基础上,重建过去近5000年抚仙湖有机质的来源和湖泊水位的变化,探讨了湖泊环境变化与区域气候变化的关系.结果表明,抚仙湖沉积物中正构烷烃n-C23n-C31可有效指示内源沉水植物和外源陆生植物.近5000年抚仙湖湖泊环境经历了3个阶段:在5000—2300 cal a BP阶段,沉水植物广泛分布,湖泊水位处于高位;在2300—2000 cal a BP阶段,抚仙湖沉积环境快速变化,内源沉水植物生物量锐减,水位快速下降;2000 cal a BP至今,沉水植物生物量持续减少,湖泊水位保持低水位;同时,人类活动也影响了该阶段(2000 cal a BP至今)陆源植物的输入.本研究重建的抚仙湖持续降低的水位变化和湖泊生产力趋势与过去5000年西南地区的年平均温逐渐降低、年平均降水量逐渐减小的总体趋势相对应,表明区域气候变化是湖泊沉积环境变化的主要驱动力.
关键词:  抚仙湖  正构烷烃  水位变化  沉水植物
DOI:10.18307/2022.0426
分类号:
基金项目:国家自然科学基金项目(41971115,41761044)和云南省基础研究专项重点项目(202101AS070006)联合资助.
Lake environmental changes over the past 5000 years recorded by multiple proxies of sediments in Lake Fuxian, southwest China
Yang Chunhe1, Yang Huan2, Zheng Pingbo1, Duan Lizeng3, Zhang Xiaonan3, Zhang Hucai3, Shen Caiming1, Sun Huiling1
1.Yunnan Key Laboratory of Plateau Geographic Processes and Environment Change, Faculty of Geography, Yunnan Normal University, Kunming 650500, P. R. China;2.Hubei Key Laboratory of Critical Zone Evolution, School of Geography and Information Engineering, China University of Geosciences, Wuhan 430074, P. R. China;3.Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, Kunming 650504, P. R. China
Abstract:
Numerous studies have been done to reconstruct the Holocene vegetation, precipitation, temperature, and lake water level using lake sediments in southwest China. However, differences in seasonal sensitivity of proxies as well as regional climate have led to great differences in paleoclimate reconstructed from different proxies and regions, more reliable records are thus essential to corroborate each other and develop a detailed picture of climate variability in southwest China. This study focused on a lacustrine sediment core (FXH-6) from Lake Fuxian in southwest China spanning the past 5000 years. Then-alkanes and sediment color were measured to determine the source of n-alkanes in the sediments and their environmental significance, and then to clarify composition changes of the inputs from terrestrial plants and submerged plants as well as to reconstruct the Lake Fuxian water level changes in the past 5000 years. Our results show that C31 and C23 n-alkanes in the sediments of Lake Fuxian can effectively indicate the input of terrestrial plants and submerged plants, i.e., the higher abundance of n-alkanes (C23) indicated the higher biomass of submerged plants in the lake, implying relatively higher lake water level. The reconstructed Lake Fuxian water level exhibited a general decrease trend during the past 5000 years with a three-stage development. The stage I at 5000-2300 cal a BP was characterized by a relatively high lake water level, as indicated by abundant n-alkanes (C23) and thus a large number of submerged plants; the stage Ⅱ at 2300-2000 cal a BP is an abrupt transition when the biomass of submerged plants decreased sharply indicating a rapid drop of lake water level and thus an abrupt change of lake environments; the stage III from 2000 cal a BP to the present was characterized by continuous declines of submerged plants and low lake water level, in which the input of terrigenous plants was also influenced by intensified human activities. The reconstructed trends of continuously decreasing Lake Fuxian water level and biomass productivity are consistent with the overall trends of decreasing mean annual temperature and precipitation in southwest China during the past 5000 years, suggesting that regional climate change is the main driving force of lake sedimentary environment change.
Key words:  Lake Fuxian  n-alkanes  lake water level change  submerged plants
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