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Subject: 地理学::自然地理学
Title: 青藏高原纳木错湖泊沉积物中的介形虫及其环境变化研究
Author: 谢曼平
Issued Date: 2009-06-03
Supervisor: 朱立平
Major: 自然地理学
Degree Grantor: 中国科学院研究生院
Place of Degree Grantor: 北京
Degree Level: 博士
Keyword: 青藏高原 ;  湖泊沉积 ;  介形虫 ;  环境变化 ;  丰度 ;  分异度 ;  转换函数
Call Number: S000020
Department: 图书馆
Abstract: 青藏高原由于其独特的地理位置和对全球环境变化的敏感响应,成为全球环境变化研究的热点地区。 青藏高原地区发育的大量冰川、湖泊及树木,为过去环境变化研究提供了良好的素材。冰芯、湖泊沉积物及树轮等成为主要研究载体,在近年来的过去全球变化研究中扮演着重要的角色。本文涉及到的研究区纳木错地处青藏高原中南部,属高原亚寒带季风半干旱气候区。目前这一地区短时间尺度高分辨率的过去环境变化研究还比较少,本文尝试利用湖泊沉积物中的介形虫这类微体生物,对这一地区的环境变化进行重建。但是由于这一地区的介形虫很大部分都是地方性属种,其生境未知,因此笔者及工作组成员采取了大量现代样品。利用现代样品的结果来反演过去环境变化。(1)本文尝试从软体部分来对介形虫种属进行鉴定,得到4类介形的软体特征及其生态环境信息。并且纠正了一部分鉴定结果:将最初的Fabaeformiscandona fabaeformis 纠正为F.danielopoli,将最初定义的Eucypris sp?纠正为Candona sp?。(2)介形虫在湖泊沉积环境研究中作为有效指标起着非常重要的作用。然而对于一些区域性或地方性的属种,由于其生境未知,一些广适种则能够忍受周遭环境发生很大范围的变化,使得很难确切的利用介形虫的组合还原其环境信息。本文针对这一缺陷,采取了不同深度的湖泊表层沉积物,发现这些沉积物中的介形存在介形类丰度和分异度的变化。因此划分为深、中、浅水三个组合。深水以L.postilirata,L.parasculpta及F.danielopoli为典型代表,丰度和分异度都很低。中等水深以L.sinensis,L.postilirata,L.parasculpta,I.sebeiensis和C.xizangensis等为代表。丰度达到最高值,分异度中等。浅水以E.gyrongensis,I.sebeiensis,L.sinensis和F.danielopoli为典型代表,丰度较低,分异度则达到最高值。(3)尽管存在相关性较差(R2=0.77)、标准误差较大(error=±10.2m)以及基础数据不足等一些缺陷,我们仍然可以将建立的古水深转换函数用于NMLC-1孔中,对过去环境,特别是古水深的变化进行比较初步的定量化研究。根据转换函数的结果,纳木错可以划分为三个阶段:早期由深水逐渐退化为浅水,中期由浅水区转化为水深逐渐变深,晚期为高湖面期。 (4)介形虫组合及其他指标综合反映的纳木错地区的环境变化可以分为三个阶段:早期(8400-6800aB.P.)纳木错地区由温暖湿润气候缓缓变化为气温下降,湖盆收缩;中期(6800-2900aB.P.)由温暖偏干浅湖期变成温凉干旱湖盆扩张期;晚期(2900-0aB.P.)的温暖干旱深湖期。公元初年的降温事件在本研究中也有呈现。表明介形虫是一个研究古气候变迁的良好指标。虽然还存在一些不足,但是本文利用介形虫这一生物指标,对纳木错地区的过去环境变化进行了恢复,对青藏高原其他湖泊的环境变化研究具有借鉴意义。关键词:青藏高原 湖泊沉积 介形虫 环境变化 丰度 分异度 转换函数
English Abstract: Tibetan plateau becomes a very attractive area for palaeoclimate and environment research due to its unique geographic location and its sensitive response to global environment changing. The developed glaciers, lakes and forests in Tibet region supply for excellent data for research on the palaeoenvironment evolution in such regions. Ice cores, lake sediments and tree rings are main research subjects, which play an important role in modern study on global palaeoenvironment changing. The research areas involved in this dissertation are located in the middle southern part of Tibetan Plateau; the climate in such areas is characterized as Plateau subfrigid zone and semiarid monsoon climate zone. Study on palaeo-environment in short-time windows with high density in such areas has not been carried out very much; the research in this dissertation is set up to reconstruct the picture of palaeoenvironments in such areas using ostracod fossils preserved in lake sediments. However, since most of the ostracodes in the study areas are endemic species and their living environments are unknown, modern sampling results are used to deduce palaeoenvironments based on the samples acquired in the areas. (1) Soft-part patterns are utilized to categorize ostracodes, which leads to four types of ostracodes and the corresponding ecological information. Some identification results have been modified: Fabaeformiscandona Fabaefromis, now as F. danielpopli, and E. sp, now as C. sp. (2) Ostracodes work as effective indicators and play a key role in this study. Usually, general species live in environments with rapid variation, which makes it less difficult to reconstruct their accurate original living environments. This is not the case for local species due to the fact that they are confined locally and their living environments are not known very well. To overcome such difficulty, sediments from various depths are sampled; and abundance and diversity are also analyzed. Based on the analysis, samples are divided into three groups: deep water, middle water and shallow water. Deep-water group is represented by L. postilirata, L. parasculpta and F. danielopoli, with low abundance and diversity. Middle-water group typically includes L. siensis, L. postilirata, L. parasculpta, I. sebeiensis and C. xizangensis, with highest abundance and medium diversity. Shallow-water group is characterized by E. gyongensis, I. sebeiensis, L. sinensis and F. danielopoli with low abundance and highest diversity. (3) Ancient water depths can still be calculated and the conversion function for this calculation can be used for NMLC1 holes though there exists insufficient information such as low cross-correlation (R2=0.77), large standard error (±10.2 m) and lack of primary data. Conversion function is used in studying ancient environments, especially ancient water-depth analysis in a quantitative way. Based on such quantitative results, the evolution of Namco region can be divided into three periods: early stage from deep water to shallow water, middle stage from shallow water to deep water gradually, late stage as a deep lake. (4) Ostracod groups and other indicators related to Namco regions result in three stages in the environment evolution in such areas: in the early stage (8400-6800aB.P.), the climate shifted very slowly to cold from a warm and humid one, leading to a shrinking lake basin; in the middle stage (6800-2900 aB.P.), the lake basin changes from a warm -dry and shallow lake to a cool- dry increasing lake; in the late stage (2900-0aB.P.), the region gradually became warm, dry and deep lake. The temperature drop around the beginning of the Christ Calendar has been noticed in the research samples, which indicates that ostracodes are good subjects for research on the ancient climate. Though there is still more work to do, the research on ostracodes in this dissertation has helped us to reconstruct ancient environments in Namco regions. This research in turn will be valuable to research on environment evolutions in other lake regions in Tibetan Plateau. Key words: Tebitan Plateau, Lacustrine sediment, ostracod, environment changing, abundance, diversity, transfer function
Language: 中文
Content Type: 学位论文
URI: http://ir.itpcas.ac.cn/handle/131C11/1236
Appears in Collections:图书馆_学位论文

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Recommended Citation:
谢曼平.青藏高原纳木错湖泊沉积物中的介形虫及其环境变化研究[博士].北京.中国科学院研究生院.2009
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