Abstract Riparian vegetation directly and indirectly affects many fluvial processes. In particular, the root system of riparian trees and shrubs may greatly influence river morphodynamics by imparting higher shear strength to riverbanks compared to unvegetated channel margins. Therefore, the bank-stabilizing role of riparian vegetation should be quantitatively considered in river restoration projects. This work aims to quantify the additional strength due to the root systems of naturally established riparian vegetation after two river restoration projects carried out in the Italian Alps (Ahr and Mareit rivers, South Tyrol). These projects represent the largest restoration interventions carried out so far in Italian rivers, and the two sites feature contrasting channel patterns along with varying river-floodplain dynamics. The mechanical properties of roots and their distribution in the floodplain soils in the two sites have been measured to estimate root cohesion distribution associated to gray alder (Alnus incana) and pioneering willows (Salix spp.). Results show that roots of plants colonizing the gravelly substrate of building islands in the Mareit River have less tensile strength than those belonging to trees growing in the floodplain of the Ahr River, rich in fine sediments. However, the higher root contribution to the overall soil strength occurs in the island site, due its lack of fine sediments.

中文翻译：

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修复河流中河岸树木的根系加固

摘要 河岸植被直接和间接影响许多河流过程。特别是，与未植被的河道边缘相比，河岸树木和灌木的根系可以通过赋予河岸更高的剪切强度来极大地影响河流形态动力学。因此，河道修复工程应定量考虑河岸植被的稳岸作用。这项工作旨在量化在意大利阿尔卑斯山（南蒂罗尔的阿尔河和马雷特河）实施的两个河流修复项目后，自然形成的河岸植被的根系所产生的额外强度。这些项目代表了迄今为止在意大利河流中进行的最大的恢复干预措施，这两个地点具有对比鲜明的河道模式以及不同的河流泛滥平原动态。测量了两个地点的根系的机械特性及其在漫滩土壤中的分布，以估计与灰桤木 (Alnus incana) 和先锋柳 (Salix spp.) 相关的根系凝聚力分布。结果表明，与生长在富含细粒沉积物的阿尔河漫滩中的树木相比，在马雷特河建造岛屿的砾石基质上定居的植物根部的抗拉强度较低。然而，由于缺乏细小的沉积物，岛屿对整体土壤强度的贡献较高。结果表明，与生长在富含细粒沉积物的阿尔河漫滩中的树木相比，在马雷特河建造岛屿的砾石基质上定居的植物根部的抗拉强度较低。然而，由于缺乏细小的沉积物，岛屿对整体土壤强度的贡献较高。结果表明，与生长在富含细粒沉积物的阿尔河漫滩中的树木相比，在马雷特河建造岛屿的砾石基质上定植的植物根部的抗拉强度较低。然而，由于缺乏细小的沉积物，岛屿对整体土壤强度的贡献较高。