Comparing mineral magnetic properties of sediments in two reservoirs in “strongly” and “mildly” eroded regions on the Guizhou Plateau, southwest China: A tool for inferring differences in sediment sources and soil erosion
Comparing mineral magnetic properties of sediments in two reservoirs in “strongly” and “mildly” eroded regions on the Guizhou Plateau, southwest China: A tool for inferring differences in sediment sources and soil erosion
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DOI：
10.1016/j.geomorph.2011.04.003
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发表时间：
2011-07
期刊：
影响因子：
3.9
通讯作者：
Hongya Wang;Lin-hai Xu;X. Sun;Minghui Lu;Xiaoya Du;Yuying Huo;I. Snowball
中科院分区：
文献类型：
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作者：
Hongya Wang;Lin-hai Xu;X. Sun;Minghui Lu;Xiaoya Du;Yuying Huo;I. Snowball
石板桥水库（0.24 km 2）和小河水库（0.28 km 2）的集水面积分别为6.00 km 2和22.69 km 2。它们基本上代表了贵州高原的“强侵蚀”区（石板桥）和“弱侵蚀”区（小河）。从这两个水库中提取了沉积物芯，并从其集水区采集了土壤样本。对沉积物和土壤进行了矿物磁性测量，并对选定的沉积物岩心和土壤剖面进行了粒度分析。SIRM与χ lf用于比较沉积物和土壤样品。此外，还检查了沉积物样品的不同粒度组分的百分比与磁性参数/比率之间的相关性。这些结果揭示了这两个代表性流域的泥沙来源和土壤侵蚀的差异。石板桥水库沉积物来源于表层土和底土。当侵蚀相对较弱时，它仅限于表土，并优先将相对较细的磁性颗粒输送到水库中，这可能意味着雨水飞溅和/或片蚀。在这个相对陡峭的集水区，更强的侵蚀力不仅能够移动相对粗糙的铁磁性颗粒从表土，但也切割底土和移动反铁磁性矿物进入水库，这似乎暗示不仅片洗，但也细沟和沟壑侵蚀。由于没有稳定的河流，也没有在这个山区集水区的渠道网络发达，河岸侵蚀产沙的贡献几乎可以忽略不计。小河水库地形较缓，沉积物主要来源于表土侵蚀。在这里，侵蚀集中在表土，并优先输送相对较细的磁性颗粒进入水库时，侵蚀力弱。然而，即使在这个相对平坦的集水区，侵蚀力增加，侵蚀仍然局限于表土。因此，相对较粗的铁磁性颗粒从表土被运到水库，但底土保持原状，并有反铁磁性矿物的沉积物中的比例没有显着变化。因此，即使在这个丘陵平原集水区的侵蚀加剧时，也只会发生片状冲刷。总体而言，石板桥流域更有效的侵蚀可能是由于其比小河流域更陡峭的地形，尽管更高、更多的季节性植被和更低的林地比例也可能导致对侵蚀力敏感性的差异。
Shibanqiao Reservoir (0.24 km2) and Xiaohe Reservoir (0.28 km2) have catchments of 6.00 km2and 22.69 km2, respectively. They essentially represent “strongly eroded” (Shibanqiao) and “mildly eroded” (Xiaohe) regions in Guizhou Plateau, southwestern China. Sediment cores were retrieved from the two reservoirs and soils were also sampled from their catchments. Mineral magnetic measurements were performed on the sediments and soils, and the particle-size analysis of selected sediment cores and soil profiles were also made. SIRM versus χlfwas used to compare sediment and soil samples. In addition, correlations between percentages of different particle-size fractions and magnetic parameters/ratios of sediment samples were also checked. These results revealed differences in sediment sources and soil erosion in these two representative catchments. The sediments in Shibanqiao Reservoir are derived from both the topsoil and subsoil. When erosion is relatively weak, it is limited to the topsoil and preferentially transports the relatively finer magnetic grains into the reservoir, which may imply rain splash and/or sheet erosion. In this relatively steep catchment, stronger erosional forces are capable of not only moving relatively coarser ferrimagnetic grains from the topsoil, but also incising the subsoil and moving anti-ferromagnetic minerals into the reservoir, which seems to hint at not only sheet-wash but also rill and gully erosion. As there are no stable streams nor channel networks developed in this mountainous catchment, contributions from river-bank erosion to sediment yield are almost negligible. The sediments in Xiaohe Reservoir, which has a lower relief, are predominately derived from topsoil erosion. Here, erosion is concentrated to the topsoil and preferentially transports the relatively fine magnetic grains into the reservoir when erosional forces are weak. However, even when erosional forces increase in this relatively flat catchment, erosion is still restricted to the topsoil. Thus, relatively coarser ferrimagnetic grains from the topsoil are transported to the reservoir, but the subsoil remains undisturbed and there are no significant changes in the proportion of anti-ferromagnetic minerals in the sediments. Consequently, only sheet-washing occurs even when erosion is intensifying in this hilly plain catchment. In general, the more effective erosion in the Shibanqiao Catchment is probably due to its steeper topography than Xiaohe Catchment, although higher and more seasonal rainfalls and lower percentages of woodlands may also contribute to the differences in susceptibility to erosional forces.