Figure 11 Relative abundance, relative height, relative coverage, and importance value of dominant species in the vegetation quadrats.
Remote sensing provides basic variables for assessing and monitoring diversity, and establishing relationships between plant diversity and spectral data has been proposed as a potential solution (Chapungu et al., 2020; Gholizadeh et al., 2020). NDVI is frequently used to assess vegetation health, greenness, and estimate vegetation species diversity. NDVI is known for its sensitivity to primary productivity, which defines spatial variations in plant diversity (Stoms & Estes, 1993; Gillespie, 2005). Numerous studies have demonstrated significant correlations between NDVI and species diversity in various regions, such as savannah biomes (Madonsela et al., 2018) and wetlands (Zhu et al., 2022). However, our study reveals that NDVI may not always be a reliable proxy for measuring diversity, DVI can be used to establish a mathematical model for monitoring vegetation diversity at our study site. The correlation between NDVI and diversity index is comparatively low compared to DVI. Furthermore, no significant correlation between NDVI and diversity index has been observed at a 30-meter scale. This may be the heightened sensitivity of NDVI to seasonal variations, rainfall, vegetation phenology, and other environmental factors that impact biodiversity (Pau, et al., 2012; Madonsela et al., 2018). Consequently, using vegetation cover or NDVI as the primary criterion for evaluating restoration effectiveness may require further evaluation regarding validity as a tool for regulatory monitoring standards (Madonsela et al., 2018; Han et al., 2021; Mi et al., 2021; Hoffmann, 2022).

4.3 Suggestions for Monitoring of Ecological Restoration in Mining Areas

In mining areas, the restoration of vegetation diversity is of fundamental importance for establishing the biotic framework for the ecosystem to commence functioning (Huang et al., 2019; Yan et al., 2019). However, current large-scale rehabilitation operations tend to prioritize simplistic mono or poly-cultures often with a preference for fast-growing species over slower growing but more biodiverse ecosystems (Liu et al., 2018; Yang et al., 2022). It is imperative to acknowledge that natural vegetation succession, particularly in areas disturbed by mining activities, is a time-consuming process that requires meticulous planning to ensure the right species are restored that enhance successional processes (Fukami and Nakajima, 2013).
Our study findings reveal a prevalence of shrub-dominated areas, particularly in the western region, where Artemisia and Salix are the primary species. Despite providing high coverage, these areas exhibit limited species diversity (Figures 5 and 7) compared with the native reference sites (Young et al., 2022). The low diversity observed in the shrub-dominated areas may indicate a shrub encroachment phenomenon, characterized by a decrease in species richness, and landscape homogenization. Although some studies argue that this shrub encroachment represents a new equilibrium state (Peng et al., 2013), with vegetation transitioning from herbaceous to shrub-dominated, others suggest that it may lead to negative consequences such as decreased plant diversity and compromised or skewed ecological functions, including water and biodiversity conservation (Liu et al., 2021; Ding and Eldridge, 2023).
Sound monitoring that is time and cost effective is crucial to inform ecological restoration, so that timely corrective actions can be implemented and adaptive management is operationalized (Young et al., 2022). This includes thoughtful vegetation configuration, species selection, seed optimization, and planting density. Integrating vegetation diversity monitoring into the assessment criteria for evaluating the effectiveness of ecological restoration projects is essential to accurately monitor post-mining restoration success and ensure local communities are supported by robust data and validated science (Hughes et al., 2018).