Micro-topography has been proved to be beneficial for plant colonization in severe environments. There are numerous micro-topographies caused by erosion of gangue dumps in the Northeast China, which can make plant colonization difficult. To determine how these micro-topographies affect plant colonization, the environment conditions, regeneration characteristics, vegetation characteristics of different erosion micro-topographies, such as bare slope, rill, ephemeral gully and deposit body were studied, and their relationships analyzed. The results showed that the content of particles with a size < 2 mm in the deposit body and bare slope was 33.7% and 7.8% higher than that in the ephemeral gully, respectively (p < 0.05), while the content of particles with a size > 20 mm in the ephemeral gully was 2.24 times higher than that in the deposit body. Except for the substrate water content, the substrate temperature and the surface humidity and temperature of the ephemeral gully were significantly different from those of the deposit body (p < 0.05); the surface temperature was the highest (54.6 °C) while the surface humidity and the substrate water content were the lowest among the erosion micro-topographies. The vegetation coverage, the plant and seedling density of the deposit body were significantly higher than those of the ephemeral gully (p < 0.05), with differences of 5.26, 35.9 and 16.8 times, respectively. The vegetation characteristics (Vdc) were more affected by the regeneration characteristics (Rc) as well as surface humidity and temperature (Sht), while Rc was significantly affected by Sht, which was extremely significantly affected by the soil physical properties and substrate water and temperature (p < 0.01). Different plant species had different responses to the environmental conditions of the erosion micro-topographies. In conclusion, the deposit body and rill are likely to promote plant colonization, which is driven mainly by the seed supply and comfortable growing conditions. The ephemeral gully is not suited to plant colonization because of its unhealthy mechanical composition and strong runoff scouring, and because it is prone to drought, high temperature, and a lack of seeds.

Restoring vegetation on waste dumps is imperative because soil erosion heavily impacts these areas and creates erosion micro-topographies, including bare slopes, rills, ephemeral gullies, and deposit bodies. These micro-topographies may affect seedling emergence by forming special micro-habitats, although the mechanism is vague. This study determined the substrate chemical (i.e., pH and electrical conductivity) and physical (i.e., capillary porosity, capillary water content, and mechanical composition) properties of different micro-topographies. In addition, the temporal dynamics of micro-climates (i.e., air temperature and air humidity), substrate hydrothermal conditions (i.e., substrate temperature and water content), and seedling emergence were investigated. Redundancy analysis (RDA), random forest (RF), and receiver operating characteristic (ROC) curve analysis were then used to identify the main factors affecting seedling emergence and clarify the relationships among the environmental conditions. Our results demonstrate that seedling densities in the rill, ephemeral gully, and deposit body were 1.78 times, 3.42 times, and 3.97 times higher than those on the bare slope, respectively. More species were found in the rill, ephemeral gully, and deposit body (Artemisia annua, Salsola collina, Setaria viridis, and Tribulus terrestris) than on the bare slope (Salsola collina). The main factors affecting seedling emergence were air humidity, substrate temperature, and substrate water content. The mechanical composition may have affected substrate water content during the initial stage of seedling emergence and substrate temperature during the entire period. We demonstrate that the ephemeral gully and deposit body may provide micro-habitats with a lower substrate temperature and higher substrate water content, which are favorable to seedling emergence, thus guiding vegetation restoration on waste dumps or other disturbed areas.