Topographic aspect affects the vegetation restoration and artificial soil quality of rock-cut slopes restored by external-soil spray seeding

External-soil spray seeding (ESSS), a technique of spraying artificial soil materials onto bare slopes for vegetation cover construction, has been widely used to restore rock-cut slopes. However, studies on the effect of the practical application of this technique on different topographic aspects have been rarely performed. In this study, two topographic aspects, namely, north-facing versus south-facing, were investigated under two railway lines, and two local natural slopes (north-facing versus south-facing) were selected as references. Vegetation and soil conditions, which are paramount aspects of ecological restoration assessment, were characterized in terms of the richness and diversity indices, vegetation canopy cover, basic soil physico-chemical properties, and structural characteristics of these slopes. Results showed that (1) the topographic aspect significantly affected the vegetation restoration and artificial soil quality of rock-cut slopes restored by ESSS; (2) the ecological restoration effect of north-facing slopes were better than that of south-facing slopes; and (3) the vegetation and soil conditions of natural slopes were better than those of rock-cut slopes. Therefore, additional scientific management measures should be implemented to promote the ecological restoration of rock-cut slopes, especially for south-facing slopes.