Characteristics of effective content of medium and trace elements in Amorpha fruticosa root soil for slope protection

During highway slope ecological restoration, selecting restoration plants is important to maintain the soil medium and trace element content, as well as to improve the slope ecological environment. In this study, Amorpha fruticosa, a typical slope protection species on expressways, was examined. Root soil was collected as the research object, and the effective content of major medium and trace elements in the rhizosphere and non-rhizosphere soils of A. fruticosa at different soil depths, and their root enrichment effects, were analyzed. The results showed that the content of trace elements such as Fe and Cu and that of medium elements such as Mg in the rhizosphere was significantly higher than that in the non-rhizosphere, while the content of Mn and Zn in the rhizosphere was significantly lower than that in the non-rhizosphere. There was no significant difference in Ca content between the rhizosphere and non-rhizosphere. With increasing soil depth, the content of Fe, Mn, Cu, and Mg decreased gradually, while that of Zn and Ca showed no obvious trend. A correlation between A. fruticosa rhizosphere and non-rhizosphere soil elements was confirmed, and Fe, Cu, Ca, and Mg were enriched to different degrees in the roots. The results showed that planting A. fruticosa on the slope of the expressway had potential effects in terms of maintaining and improving medium and trace element content in the soil and resisting slope soil erosion.