## 4 Discussion
In contrast, the survival of _Robinia pseudoacacia_ seedlings was positively correlated with the number of heterospecific seedlings and mature trees but negatively correlated with the number of heterospecific mature trees. This indicates that _Robinia pseudoacacia_ seedlings may benefit from facilitation by certain species while being suppressed by competition from others. These findings highlight the importance of species interactions in shaping community dynamics, supporting the theory of density-dependent regulation in plant populations [40,41]. While biotic factors were dominant, certain abiotic factors, such as elevation and slope, also had significant negative correlations with sapling survival. These findings suggest that topographic conditions impose substantial constraints on tree regeneration in the region. Steeper slopes may be associated with lower soil moisture retention and increased erosion, reducing the establishment success of young trees [42,43]. Future studies should incorporate additional abiotic variables--such as soil properties (e.g., nutrient availability, pH, and moisture content) and microtopography--to provide a more comprehensive understanding of seedling and sapling dynamics in reclaimed mining areas. By analyzing seedling and sapling abundance, spatial distribution, and survival drivers, this study contributes valuable data for understanding vegetation dynamics in reclaimed mining areas. The findings provide a scientific basis for optimizing species selection and community reconstruction in similar mining reclamation sites. Specifically, the observed competitive dominance of _Ulmus pumila_ suggests that it may be a key species for future restoration efforts. However, its potential impact on biodiversity and community structure should be carefully evaluated. This study also underscores the importance of long-term ecological monitoring in assessing restoration success. While the four-year interval (2019-2024) provides valuable insights, a longer study period is necessary to capture broader successful trends and interactions among species. The positive correlation between _Robinia pseudoacacia_ and certain species may originate from mutually beneficial allelopathic effects. For instance, flavonoids released by leguminous plants can enhance nitrogen fixation by symbiotic bacteria. Allelopathic effects, through suppressing competitors or modifying microbial communities, may explain the interplant interaction patterns observed in _Robinia pseudoacacia_ seedlings. Additionally, future research should expand the scope of analysis to include a more comprehensive set of environmental factors, such as soil characteristics (e.g., organic matter content, microbial diversity, and soil content), hydrological conditions (e.g., groundwater availability, precipitation variability, and water availability), and microclimatic influences (e.g., temperature fluctuations and wind exposure) [44,45]. The Digital Hemisphere Photography method adopted in this study is widely used in light measurement but its assumption that the canopy openings are evenly distributed within the quadratic is controversial. Although statistical methods were used in this study for statistical error correction, some studies have shown that the light intensity can significantly change due to differences in canopy structure within 1 m, and the central point measurement of the 10 m \(\times\) 10 m quadrate may ignore the influence of local shadows or light-transmitting patches [46]. Therefore, in future studies, multi-scale illumination measurement can be added to supplement the illumination data of small-scale plots (such as a 1 m \(\times\) 1 m sub-quadrangle, or the mobile hemispheric photography system can be used to shoot multiple points along the diagonal of the quadrangle to capture the spatiotemporal heterogeneity of illumination.