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).