Radionuclide dating of recent sediment and the validation of pollen-environment reconstruction in a small watershed reservoir in southeastern China
Radionuclide dating of recent sediment and the validation of pollen-environment reconstruction in a small watershed reservoir in southeastern China
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中国东南部小流域水库近期沉积物放射性核素测年及花粉环境重建验证
DOI：
10.1016/j.catena.2013.11.010
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发表时间：
2014-04-01
期刊：
影响因子：
6.2
通讯作者：
Huang, Xulei
中科院分区：
文献类型：
--
作者：
Chen, Bishan;Zheng, Zhuo;Huang, Xulei
从黄洞水库（中国东南部）采集了一个76 cm的沉积物柱样。应用放射性核素Cs-137和Pb-210以及沉积物粒度分析来建立年代学和现代沉积速率。Cs-137时间标志物建立的年代学与恒流恒沉模型（CFCS）和由54 cm深度沉积物粒度曲线确定的已知建坝时间（1960 AD）相一致。结果表明，黄洞水库淤积速率较大，水土流失严重。建库前沉积速率约为1.5 cm/a，属河流漫滩存款。在水库沉积期间（自20世纪60年代以来），速率下降到约1.0 cm/a。花粉和微炭分析进行了测试花粉为基础的环境重建的可靠性，包括植被覆盖，森林砍伐，种植和火灾。花粉和微炭分析结果表明，草本植物（主要是禾本科）、蕨类植物（如芒萁属）和几种树木（主要是松属）的变化与地方志或历史记载有关。我们发现，当地森林覆盖变化的最重要的指标是花粉浓度和AP/NAP值（乔木花粉与非乔木花粉的比例）。人类对森林的影响表现在树木花粉百分比和绝对花粉浓度的急剧下降。用木炭浓度峰值和C/P值（木炭浓度与花粉浓度的比值）记录森林火灾事件。例如，在大跃进运动和文化大革命期间的大规模砍伐森林和密集的火灾是由花粉和微木炭光谱反映的。这项工作证明了放射性核素作为测年方法在中国南方是适用的，而Cs-137方法尽管绝对值较低，但在小型水库环境中显示了其可靠性。粒度、花粉和木炭等环境指标对自然灾害或人类活动引起的当地生态系统变化具有足够的敏感性。皇冠版权所有（C）2013由爱思唯尔B. V.出版保留所有权利。
A 76 cm sediment core was collected from the Huangdong Reservoir (southeastern China). The radionuclides Cs-137 and Pb-210 and sediment grain size analysis were applied to establish the chronology and modem sedimentation rates. The chronology established by the Cs-137 time markers was consistent with the Constant Flux Constant Sedimentation (CFCS) model and the known time of dam construction (1960 AD) recognized from the curve of sediment grain size at the depth of 54 cm. The results show that the sedimentation rate of the Huangdong Reservoir is relatively high, implying that soil erosion and water loss were strong. The sedimentation rate before the construction of the reservoir was approximately 1.5 cm/a, which belongs to the fluvial flooding deposit. The rate decreased to approximately 1.0 cm/a during the reservoir deposition (since 1960s). Pollen and micro-charcoal analysis were performed to test the reliability of pollen-based environment reconstruction, including vegetation cover, deforestation, planting and fire disasters. The results of pollen and micro-charcoal indicated that the herbs (primarily Gramineae), ferns (such as Dicranopteris) and several trees (mainly Pinus) varied following chorography or historical records. We discovered that the most important indicators for local forest-cover changes are pollen concentration and the AP/NAP value (ratio of arboreal pollen to non-arboreal pollen). Human impact on forests is manifested by a sharp decrease in pollen percentage of trees and absolute pollen concentration. Forest fire events were recorded by the peaks of charcoal concentration and the C/P value (ratio of charcoal concentration to pollen concentration). For example, the massive deforestation and intensive fires during the Great Leap Forward movement and the Cultural Revolution are reflected by pollen and micro-charcoal spectra. This work testifies that radionuclide use as a dating method is applicable in southern China, and the Cs-137 method has demonstrated its reliability in the small reservoir setting in spite of low absolute values. The environmental proxies, such as grain size, pollen, and charcoal, are sufficiently sensitive to reveal local ecosystem changes caused by natural disasters or human activity. Crown Copyright (C) 2013 Published by Elsevier B.V. All rights reserved.