Sediment transport and carbon sequestration characteristics along mangrove fringed coasts
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摘要: 红树林在碳沉降和捕获沉积物方面扮演着重要的角色.然而,由于对植被边界沉积过程的认识还非常有限,因此人们对红树林这种功能的效率仍不十分明确.为了了解红树林对于沉积物输运和有机碳沉降的效果,研究者对雷州半岛沿岸的4个典型红树林区域中的3个植被带进行了调查.调查结果显示,沉积物输运对于植被摩擦阻力通常是非常"敏感"的.沉积物输运模式的转换趋势可以从光滩到内部/边缘区的累积频率曲线上分辨出.植被覆盖同时也帮助了捕获沉积物质,从而导致内部林表层沉积物有机碳的显著富集.然而,柱状沉积物样品的粒度参数反映出不同站位沉积过程随着时间发生了剧烈变化.虽然各站位沉积环境均处于河流-海洋转换带的相同能量水平,沉积物的构成却从砂到泥的变化非常大.基于PCA结果,各站位和深度的沉积物特征变化主要反映在平均粒径或有机碳参数上.此外,深度和δ13C值之间的高度相关性也反映出红树林来源的有机碳库存比例随时间而增加.Abstract: Mangroves play an important role in sequestering carbon and trapping sediments. However, the effectiveness of such functions is unclear due to the restriction of knowledge on the sedimentation process across the vegetation boun-daries. To detect the effects of mangrove forests on sediment transportation and organic carbon sequestration, the granulometric and organic carbon characteristics of mangrove sediments were investigated from three vegetation zones of four typical mangrove habitats on the Leizhou Peninsula coast. Based on our results, sediment transport was often "environmentally sensitive" to the vegetation friction. A transition of the sediment transport mode from the mudflat zone to the interior/fringe zone was often detected from the cumulative frequency curve. The vegetation cover also assists the trapping of material, resulting in a significantly higher concentration of organic carbon in the interior surface sediments. However, the graphic parameters of core sediments reflected a highly temporal variability due to the sedimentation process at different locations. The sediment texture ranges widely from sand to mud, altho-ugh the sedimentary environments are restricted within the same energy level along the fluvial-marine transition zone. Based on the PCA results, the large variation was mainly attributed to either the mean grain size features or the organic carbon features. A high correlation between the depth and δ13C value also indicated an increasing storage of mangrove-derived organic carbon with time.
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Key words:
- mangroves /
- grain size distribution /
- sedimentary organic carbon /
- Leizhou Peninsula
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