Key Takeaways & Executive Findings
- •• • Medium MBG ratio (1:2 v/v) significantly increased fungal Shannon index and evenness (p<0.05), while high ratio (1:1) suppressed bacterial diversity, indicating a non-linear dose-response and optimal application threshold. • • MBG addition enriched Cyanobacteria and beneficial functional groups (e.g., nitrogen-fixing bacteria, Bacillus), enhancing nutrient cycling potential in degraded mine soil. • • Co-occurrence network analysis showed that the medium ratio (1:2) maximized network complexity, modularity, and average degree for both bacteria and fungi, suggesting improved microbial community stability and resilience. • • Functional prediction revealed significant enrichment of pathways for lipopolysaccharide biosynthesis, nitrotoluene degradation, and plant-pathogen interactions under medium MBG, alongside increased saprotrophic and ectomycorrhizal fungi, indicating enhanced organic matter decomposition and plant-microbe symbiosis.
Abstract
Mining activities cause severe soil degradation and microbial diversity loss, impeding ecological restoration. This study evaluated the effects of a novel soil amendment, microporous bio-gravel (MBG), on bacterial and fungal community structure and function in degraded soil from the Baiyinhua open-pit mine, Inner Mongolia. A pot experiment with four MBG-to-soil volume ratios (CK, L=1:3, M=1:2, H=1:1) was conducted, with a simplified plant community and uniform fertilization. After 180 days, soil samples were analyzed via high-throughput sequencing and bioinformatics. Results showed that the medium ratio (M) significantly increased fungal Shannon index and evenness, while the high ratio (H) negatively affected bacterial communities. At phylum and genus levels, MBG promoted enrichment of Cyanobacteria and specific functional groups (e.g., nitrogen-fixing bacteria, Bacillus). Co-occurrence network analysis revealed peak complexity, modularity, and average degree in bacterial and fungal networks under the M treatment. Functional prediction indicated significant enrichment of pathways related to lipopolysaccharide biosynthesis, nitrotoluene degradation, and plant-pathogen interactions, alongside increased abundance of saprotrophic and ectomycorrhizal fungi. Mantel and VPA analyses showed that MBG indirectly regulated microbial community structure by improving soil physicochemical properties and plant traits, with stronger effects on fungi than bacteria. In conclusion, MBG optimizes the soil microhabitat and plant-soil-microbe interactions, modulating microbial diversity, network complexity, and functional potential. The medium ratio (1:2) was most effective, demonstrating potential for ecological restoration of degraded mine soils.
1. Introduction
Mining operations have left vast areas of degraded land, with China alone reporting over 2.88 million hectares of damaged mine sites. These soils suffer from compaction, nutrient depletion, and heavy metal contamination, severely limiting natural ecosystem recovery. Conventional remediation strategies—physical, chemical, and biological—are often costly, slow, and may introduce secondary pollution, hindering large-scale application. There is a pressing need for cost-effective, eco-friendly soil amendments that can restore soil function and promote microbial recolonization.
Microporous bio-gravel (MBG), a composite material with high specific surface area and porous structure, has shown promise in water treatment but its application in soil remediation remains underexplored. This study addresses this gap by systematically evaluating MBG's impact on soil microbial communities in degraded mine soil. By testing different application ratios, we identify an optimal dose that enhances microbial diversity and network complexity, offering a practical solution for mine soil restoration.
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WANG Jingwen, HU Hao, LIU Yongjie, LI Jingguo, QU Laiye, ZHANG Naili, TAO Siqi (2026). Application of Microporous Bio-Gravel for Microecological Remediation of Degraded Mine Soils. Chinese Journal of Environmental Engineering. https://doi.org/10.12030/j.cjee.202512014
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Frequently Asked Questions
What is the optimal application ratio of microporous bio-gravel for enhancing microbial diversity in degraded mine soils?
The medium ratio (1:2 v/v MBG-to-soil) was optimal, significantly increasing fungal Shannon index and evenness while maintaining bacterial diversity. Higher ratios (1:1) negatively impacted bacterial communities, indicating a threshold effect.
How does microporous bio-gravel influence soil microbial community structure and function?
MBG promotes enrichment of Cyanobacteria and beneficial functional groups (e.g., nitrogen-fixing bacteria, Bacillus). It also enhances network complexity and modularity, and enriches pathways related to nutrient cycling and pollutant degradation, as shown by functional prediction.
What are the mechanisms by which microporous bio-gravel affects microbial communities?
MBG improves soil physicochemical properties (e.g., aeration, water retention) and plant growth, indirectly shaping microbial communities. Mantel and VPA analyses indicated that MBG's effects on fungi were stronger than on bacteria, likely due to improved plant-soil-microbe interactions.
Are there any potential risks or negative effects associated with high application rates of microporous bio-gravel?
High application rates (1:1) led to a negative response in bacterial communities, possibly due to excessive alteration of soil porosity or nutrient imbalances. This underscores the need for dose optimization to avoid unintended ecological consequences.
What is the practical significance of this study for large-scale mine soil remediation?
The study demonstrates that MBG at a 1:2 ratio can effectively enhance microbial diversity and functional potential, offering a cost-effective and eco-friendly amendment. These findings support its application in field-scale restoration projects, though further validation under field conditions is needed.
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