Mineral-solubilizing microbial inoculant positively affects the multifunctionality of anthropogenic soils in abandoned mining areas

Abstract

The mining industry has a significant negative impact on ecosystems, and the remediation of abandoned mining sites requires effective strategies. One promising approach is the incorporation of mineral-solubilizing microorganisms into current external soil spray seeding technologies. These microorganisms possess the ability to decrease mineral particle sizes, promote plant growth, and enhance the release of vital soil nutrients. However, most previous studies on mineral-solubilizing microorganisms have been conducted in controlled greenhouse environments, and their practical application in field settings remains uncertain. To address this knowledge gap, we conducted a four-year field experiment at an abandoned mining site to investigate the efficacy of mineral-solubilizing microbial inoculants in restoring derelict mine ecosystems. We assessed soil nutrients, enzyme activities, functional genes, and soil multifunctionality. We also examined microbial compositions, co-occurrence networks, and community assembly processes. Our results demonstrated that the application of mineral-solubilizing microbial inoculants significantly enhanced soil multifunctionality. Interestingly, certain bacterial phyla or class taxa with low relative abundances were found to be key drivers of multifunctionality. Surprisingly, we observed no significant correlation between microbial alpha diversity and soil multifunctionality, but we did identify positive associations between the relative abundance and biodiversity of keystone ecological clusters (Module #1 and #2) and soil multifunctionality. Co-occurrence network analysis revealed that microbial inoculants reduced network complexity while increasing stability. Additionally, we found that stochastic processes played a predominant role in shaping bacterial and fungal communities, and the inoculants increased the stochastic ratio of microbial communities, particularly bacteria. Moreover, microbial inoculants significantly decreased the relative importance of dispersal limitations and increased the relative importance of drift. High relative abundances of certain bacterial and fungal phyla were identified as major drivers of the microbial community assembly process. In conclusion, our findings highlight the crucial role of mineral-solubilizing microorganisms in soil restoration at abandoned mining sites, shedding light on their significance in future research endeavors focused on optimizing the effectiveness of external soil spray seeding techniques.