Research on the composition and properties of soil substrates for ecological restoration of rocky slopes

[Objective]With the rapid development of the economy in China, the exploration of mineral resources, construction of roads, electricity and other infrastructure have produced a massive number of rocky slopes, which have a serious impact on the regional ecosystem. Because of the simple process, economy and high efficiency, the external-soil spray seeding is widely used in the ecological restoration of rocky slopes. However, the poor adhesion and stability of traditional spraying soil substrates lead to unsustainable restoration of rocky slopes. Therefore, there is an urgent need to develop targeted ecological restoration soil substrates. [Methods]In this study, we analyzed the properties of soil substrates with different compositional components, including substrate water retention, horizontal shrinkage, weight capacity, plant germination number, and plant height through pot experiments and orthogonal experiments, and screened the soil substrate with excellent performance. On the basis of the above study, the erosion resistance of the screened soil substrates was analyzed through the erosion resistance test, and the optimal soil substrate suitable for ecological restoration of high steep rocky slopes was further screened. [Results]The results showed that moderate content of water retaining agent increased the germination rate and height of plants, while slightly higher content of binder (greater than 0.15%) not only decreased the height of plants, but also reduced its growth rate. The properties of the soil substrates with different compositions differed significantly, but almost all indicators were better than those of the natural soil in the blank control group. After screening, the soil substrates in groups P6, P10, P16, P1 and P15 showed good plant growth, physical structure and water retention. Substrate loss increased significantly with increasing slope and rainfall intensity, and soil substrates in groups P15 had superior erosion resistance. [Conclusions]Therefore, the soil substrate can be directly applied to the ecological restoration of rocky slopes when the slope gradient is small (up to 60°) or when there are occasional heavy rainfalls. When the slope gradient is large (60° or more) or when there are frequent heavy rainfalls, the soil substrate should be paired with engineering applications such as protective netting.