末次冰消期泸沽湖孢粉记录的植被演替与气候变化

发布时间：2018-01-17 01:16

本文关键词：末次冰消期泸沽湖孢粉记录的植被演替与气候变化　出处：《云南师范大学》2016年硕士论文　论文类型：学位论文

【摘要】：末次冰消期是末次盛冰期向全新世的过渡阶段,末次冰消期气候的研究对认识地球气候系统如何从一个状态快速的转化到另一个状态具有重要意义,也有利于对未来气候变化趋势预测。地处我国西南云贵高原,受西南季风和东亚季风的双重影响,对气候变化极为敏感,是研究快速气候变化的理想地点。本文选择泸沽湖作为研究对象,通过湖泊钻孔岩芯的高分辨率孢粉分析,在以AMS14C测年数据建立的年代框架基础上,重建了泸沽湖流域末次冰消期的植被演替和气候变化。本文得出以下几点结论:1、泸沽湖独特的地理位置和湖泊特征决定了人类对泸沽湖流域干扰少,流域面积大且只有一个出水口,沉积稳定,有利于环境研究和植被与气候的重建。2、泸沽湖周围表土样的花粉分析表明,表土花粉谱既反映了区域性植被的总体特征,也显示了其地方性植被特性,因此,泸沽湖沉积物的化石花粉谱能反映泸沽湖流域的区域植被。3、泸沽湖地层高分辨率的孢粉分析显示,钻孔年代从老到新可花粉带划分为四个孢粉带。不同孢粉带变化的特征主要是以乔灌木花粉和草本花粉含量的此消彼长为特点。第I阶段,即16500-16000 a BP乔灌木花粉含量及较高,草本植物花粉含量较低;第II阶段,16000-15500 a BP乔灌木花粉在前一阶段基础上增加,草本花粉含量减少;第III阶段,15500-14500 a BP乔灌木花粉含量变化不大,草本花粉含量较低;第IV阶段,14500-13500 a BP,乔灌木花粉含量达最大,其中松属花粉占主导,草本花粉含量下降。4、泸沽湖LGH-2钻孔5.2-5.8m沉积岩芯的孢粉分析表明,泸沽湖流域气候在末次冰消期经历了4次阶段性的变化。16500~16000 a BP阶段,相当于末次冰消期早期,此段时期气候寒冷且气温呈逐渐增加趋势,湿度较大,降水相对较多;16000~15500 a BP阶段,相当于B?lling-Aller?d暖期前阶段,气温回升,湿度增加,气候向更为适宜的阶段发展;15500-14500 a BP阶段,相对于B?lling-Aller?d暖期,气温回升到末次冰消期的最大值,湿度最大,植被最为繁茂;14500-13500 a BP阶段,相当于B?lling-Aller?d暖期后阶段,气温仍高。在末次冰消期,泸沽湖流域经历数次持续数百年的冷事件,有的可能与全球性的H1事件有关,有的可能仅是泸沽湖流域的地区性事件。5、通过对泸沽湖流域末次冰消期气候变化与其它地区的气候记录的对比研究,探讨了末次冰消期气候变化的机制:冰消期初期气候冷湿的原因可能是受到北大西洋冰筏事件影响从而导致的温盐环流受阻,全球水汽和热量的流通减弱所致;冰消期中后期,气候主要受太阳辐射控制,温度上升,湿度增加。
[Abstract]:The last ice extinction period is the transition period from the last glacial peak to the Holocene. The study of the climate in the last ice extinction period is of great significance in understanding how the climate system of the earth rapidly transforms from one state to another. It is also beneficial to predict the future climate change trend. It is located in the southwest Yungui Plateau of China and is sensitive to climate change because of the influence of the southwest monsoon and the East Asian monsoon. Lugu Lake is an ideal place to study rapid climate change. In this paper, Lugu Lake is selected as the research object, and based on the AMS14C dating data, the high-resolution sporopollen analysis of the borehole core of the lake is carried out. The vegetation succession and climate change during the last ice elimination period in Lugu Lake basin were reconstructed. The following conclusions are drawn: 1. The unique geographical location and lake characteristics of Lugu Lake determine that the human disturbance to the Lugu Lake basin is less. The basin has a large area and only one outlet, and the deposition is stable, which is conducive to environmental research and vegetation and climate reconstruction. 2. Pollen analysis of surface soil samples around Lugu Lake shows. The pollen spectrum of topsoil not only reflects the general characteristics of regional vegetation, but also shows the characteristics of local vegetation. Therefore, the fossil pollen spectrum of Lugu Lake sediments can reflect the regional vegetation of Lugu Lake basin. The high resolution sporopollen analysis of Lugu Lake strata shows that. The pollen belt from old to new can be divided into four pollen belts. The variation of different pollen bands is mainly characterized by the variation of pollen content of tree shrub and herb pollen. The pollen content of shrub was 16500-16000a and the pollen content of herbaceous plants was lower than that of herbaceous plants. In the second stage, the pollen content of herbaceous pollen decreased from 16000-15500 a BP. In the III stage, the pollen content of shrubs and shrubs of 15500-14500a BP did not change much, but the pollen content of herbaceous plants was lower. In stage IV, the pollen content of trees and shrubs reached the highest between 14500-13500a BP.The pollen content of Pinus dominated and the pollen content of herbaceous decreased by 4. 4. The sporopollen analysis of the sedimentary core from 5.2-5.8 m in LGH-2 borehole of Lugu Lake shows that. The climate of Lugu Lake basin experienced four stages, I. e., 16500 ~ 16000a BP stage, which was equivalent to the early stage of the last ice extinction period. In this period, the climate is cold and the temperature is increasing gradually, the humidity is larger, and the precipitation is relatively more. 16000m 15500a BP stage, equivalent to B? Lling-Aller? D in the pre-warm period, the temperature rises, the humidity increases, and the climate develops to a more suitable stage (15500-14500a BP), relative to B? Lling-Aller? D warm period, the temperature rose to the maximum of the last ice extinction period, the maximum humidity, the most luxuriant vegetation 14500-13500 a BP stage, equivalent to B? Lling-Aller? During the last ice extinction period, the Lugu Lake basin experienced several cold events lasting for hundreds of years, some of which may be related to the global H1 event. Some of them may be only regional events in Lugu Lake basin. Through the comparative study of climate change in the last ice extinction period of Lugu Lake basin and other regions climate records are compared. The mechanism of climate change in the last ice extinction period is discussed. The reason of the cold and wet climate in the early ice extinction period may be caused by the blockage of the temperature-salt circulation caused by the ice raft events in the North Atlantic and the weakening of the global water vapor and heat flow. The climate was mainly controlled by solar radiation, temperature increased and humidity increased.
【学位授予单位】：云南师范大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：P532;Q914

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