The roles of rare and abundant microbial species in the primary succession of biological soil crusts are differentiated in metal tailings ponds with different states

Tailings ponds formed by long-term accumulation of mineral processing waste have become a global environmental problem. Even worse, tailings ponds are often simply abandoned or landfilled after they cease to be used. This allows pollution to persist and continue to spread in the environment. The significance of primary succession mediated by biological soil crusts for tailings pond remediation has been illustrated by previous studies. However, the process of primary succession may not be the same at different stages during the lifetime of tailings ponds. Therefore, we investigated the environmental differences and the successional characteristics of microbial communities in the primary successional stage of tailings ponds at three different states. The results showed that the primary succession process positively changed the environment of tailings ponds in any state of tailings ponds. The primary successional stage determined the environmental quality more than the state of the tailings pond. In the recently abandoned tailings ponds, abundant species were more subjected to heavy metal stress, while rare species were mainly limited by nutrient content. We found that as the succession progressed, rare species gradually acquired their own community space and became more responsive to environmental stresses. Rare species played an important role in microbial keystone species groups. Tailings ponds from mining are distributed globally and cause many environmental hazards. The spontaneous primary succession within the tailings ponds is crucial for the ecological restoration of the area. Tailings ponds in different states (in operation or stopped using for different times) have different environmental characteristics. This determines that the primary successional processes may also be different. This has never been studied before. We explored the environmental characteristics of tailings ponds in different states. Differences in microbial community succession processes were also illustrated. This study contributes to the development of pollution control and remediation programs for tailings ponds under different operating states.