Three-dimensional canopy structure dynamics of plant communities under different planting configurations in an open-pit coal mine

Canopy three-dimensional (3D) structure is a key indicator of the spatial organization and ecological functions of vegetation communities. However, accurate monitoring and quantitative assessments of canopy 3D structure under different planting configurations in mining areas remain limited. Taking the spoil dump of the Heidaigou open-pit coal mine as the study area,this study integrated UAV-based LiDAR and hyperspectral data to establish a 3D canopy structural index system,aiming to reveal the differences and successional dynamics of canopy structure under various planting patterns. The results showed that: (1) UAV LiDAR effectively extracted vegetation height information (R² = 0. 99) and enabled fine-scale individual tree crown segmentation. (2) Significant differences in canopy structure were observed among planting configurations. Poplar communities exhibited the highest structural heterogeneity;their canopy height increased progressively with restoration age and stabilized after 16 years. Pine and pine-apricot mixed communities showed relatively higher canopy cover and leaf area index,indicating stronger canopy closure,while sea-buckthorn communities had the loosest structure with the highest porosity. (3) Planting configuration significantly influenced vegetation recovery within canopy gaps. The poplar-pine mixed community supported higher gap-understory canopy cover and structural heterogeneity,which were more conducive to understory vegetation development. (4) In the early stages of ecological restoration,vertical growth of vegetation was positively coordinated with horizontal crown expansion and physiological health at the individual-tree level. Canopy height, porosity, and canopy cover were key factors affecting structural heterogeneity,with canopy height having the strongest explanatory power (ΔR² = 0. 183). Overall,the LiDAR-based 3D structural index system effectively captured the successional patterns of plant communities. Future research should further investigate the effects of three-dimensional planting arrangements on community succession.