Soil nutrients and heavy metals jointly shape spontaneous plant functional groups in abandoned mining areas

Ecological recovery of abandoned mining areas requires developing and implementing effective nature-based solutions. However, ecological processes that underlie the establishment, development, and long-term persistence of plant functional groups within natural plant communities remain poorly understood. Here, we hypothesized that local plant species in abandoned mining areas respond to the harsh environmental conditions of contaminated soils by adjusting their functional traits and survival strategies, thereby enhancing the stability of spontaneous plant communities through the development of distinct plant functional groups. To test this hypothesis, we assessed the responses of plant functional groups to heavy metal contamination and identified both environmental factors and functional traits that influence these plant functional groups. We found that heavy metal pollution induced shifts in plant functional groups and overall community composition. Specifically, stress-tolerant plant abundance fluctuated and declined; ruderal plant abundance initially decreased before increasing; and competitor plant abundance increased. The environmental factors that influenced plant functional group abundance include soil pH, heavy metal concentrations, and nutrient content. Overall, our results specifically indicate that the successional replacement of plant functional groups and the ecological recovery of plant communities in abandoned mining areas depend on soil total nitrogen levels.