Dong-sheng Bai’s research while affiliated with Southwest University of Science and Technology and other places

To investigate the characteristics of soil bacterial communities and ecosystem functions of different reclaimed vegetation types in reclaimed mine sites, we selected the surface soils of vegetation areas with no vegetation cover (CK), herbaceous plants (GL), poplar (GPL), and mixed forests (ML) as the research objects in this paper, and analyzed the characteristics of soil bacterial community diversity and composition and potential functions of soil bacterial communities in different vegetation types through high-throughput sequencing of 16S rRNA genes, and fitted a comprehensive fertility index through principal component analysis (PCA) to comprehensively evaluate the quality of soil fertility in various aspects. The results showed that: (1) There were significant differences ( p < 0.05) in soil physicochemical characteristics among different vegetation types, with ML mixed forests having the highest organic carbon and total nitrogen contents and the lowest electrical conductivity. Soil effective phosphorus and effective potassium were highest in the GL herbaceous area, with significantly higher soil sucrase and urease activities. (2) Soil bacterial community characteristics differed significantly ( p < 0.05) among vegetation types, with higher soil bacterial community diversity in GL herbaceous plants and lower diversity but highest co-occurrence network complexity in ML mixed forests; (3) KEGG enrichment analysis showed that the abundance of pathways related to carbon, nitrogen and sulphur metabolism were all higher in the soil of GL herbaceous plants, and lowest in GPL poplar; (4) The results of the integrated fertility index fitting showed that the integrated fertility index of soil ponds was highest in the soil of GL herbaceous plants, and lower in the other types of soils. In summary, different vegetation restoration types were able to improve soil quality and soil bacterial community diversity, and the herbaceous-restored surface soil had higher levels of fertility and bacterial community function, providing empirical data for subsequent vegetation restoration in the area.

To elucidate the effects of long-term (20 years) afforestation with different woody plant species on the soil microenvironment in coal gangue polymetallic contaminated areas. This study analyzed the soil physicochemical properties, soil enzyme activities, soil ionophore, bacterial community structure, soil metabolite, and their interaction relationships at different vertical depths. Urease, sucrase, and acid phosphatase activities in the shallow soil layers increased by 4.70–7.45, 3.83–7.64, and 3.27–4.85 times, respectively, after the restoration by the four arboreal plant species compared to the plant-free control soil. Additionally, it reduced the content of available elements in the soil and alleviated the toxicity stress for Cd, Ni, Co, Cr, As, Fe, Cu, U, and Pb. After the long-term restoration of arboreal plants, the richness and Shannon indices of soil bacteria significantly increased by 4.77–23.81% and 2.93–7.93%, respectively, broadening the bacterial ecological niche. The bacterial community structure shaped by different arboreal plants exhibited high similarity, but the community similarity decreased with increasing vertical depth. Soils Zn, U, Sr, S, P, Mg, K, Fe, Cu, Ca, Ba, and pH were identified as important influencing factors for the community structure of Sphingomonas, Pseudarthrobacter, Nocardioides, and Thiobacillus. The metabolites such as sucrose, raffinose, L-valine, D-fructose 2, 6-bisphosphate, and oxoglutaric acid were found to have the greatest effect on the bacterial community in the rhizosphere soils for arboreal plants. The results of the study demonstrated that long-term planting for woody plants in gangue dumps could regulate microbial abundance and symbiotic patterns through the accumulation of rhizosphere metabolites in the soil, increase soil enzyme activity, reduce heavy metal levels, and improve the soil environment in coal gangue dumps. Graphical abstract

Aims To elucidate the dominant effects of long-term restoration of different woody plants on the reconstitution of multiple environmental and biological factors in vertical soils of coal mining areas. Methods Soil physicochemical properties, soil enzyme activities, soil ionophore, microbial community structure, and soil metabolite distribution characteristics and interaction networks were analyzed at different vertical depths after long-term restoration (20 years) of four woody plant species in the coal mine area. Results (1) Phytoremediation increased the soil urease, sucrase, and acid phosphatase activities by 4.23–8.82, 4.52–8.29, and 3.28–5.26 times at 10 cm depth. It also reduced the active element content in the soil, and alleviated the mine toxicity stress of S, Fe, As, Pb, and U in the soil. (2) The Richness index and Shannon index of soil microorganisms increased by 4.77–23.81% and 2.93–7.93% after long-term restoration of woody plants, and the bacterial ecological niche was broadened. The microbial community structure shaped by different woody plants was highly similar, but the community similarity decreased with the increase in relative distance at vertical depth. Soil Cu, Fe, Mo, Na, and pH were important influencing factors of community structure for Sphingomonas, Pseudarthrobacter, Nocardioides, and Thiobacillus. (3) Woody plant restoration increased the abundance of soil metabolites (10 cm depth), and induced metabolites such as Organooxygen compounds, Carboxylic acids and derivatives, and Fatty Acyls as the main microbial regulators. Conclusions Woody plants have different patterns of environmental and biometabolic factor configurations for different depths of soil during mine restoration.

Changes in the soil ecological microenvironment of coal gangue contaminated areas were evaluated after 10 years of in situ restoration with Artemisia sacrorum, Imperata cylindrica, and Populus spp. The changes in soil enzyme activity, ion spectrum, bacterial community structure and function, and metabolic spectrum were analyzed in an unrestored coal gangue pollution area (Control), an Artemisia sacrorum + Imperata cylindrica remediation area (T1), and a Populus remediation area (T2). Phytoremediation significantly increased the soil acid phosphatase activity by 4.62–7.36 times, and decreased the electrical conductivity by 6.2–85.5%. The overall reduction trend for heavy metals in the soil was shallow layer > middle layer > deep layer, with significant reductions seen for Cs, As, Co, Pb, Ni, U, and Cr. The number and diversity of shallow soil microbial communities increased significantly, with Actinobacteria, which participate in the carbon and nitrogen cycles, and Proteobacteria, which can tolerate/metabolize multiple heavy metals, becoming the dominant species in the restoration area. Microbial genes for glycosyltransferase, transcriptional regulators, and toluene degradation changed significantly. Phytoremediation by both remediation strategies significantly changed the metabolic level of lipids and lipid-like molecules in the soil, while significantly enriching the pathways of ABC transporters and galactose metabolism, which are essential for soil detoxification, ion transport, and carbon cycling. Bacteria such as Thiobacillus and Pseudarthrobacter were important drivers of soil metabolism. In general, the in situ phytoremediation of soil contaminated by coal gangue improved the overall soil ecological microenvironment.

Phytoremediation is a means of remediation of coal gangue pollution. However, the molecular mechanism of the effect of long-term plant restoration on soil microecology has not been elucidated. This study explored the mechanism of soil-microbe-metabolite interaction after long-term recovery of Caragana korshinskii Kom. We analyzed the physical and chemical properties, enzyme activities, microbial community structure, metabolome and ionomics of the shallow (10 cm), middle (50 cm) and deep (100 cm) rhizosphere and bulk soils after C. korshinskii restoration for 10 years. The activities of soil urease, sucrase, and acid phosphatase mainly increased in the rhizosphere area of C. korshinskii. The microbial abundance increased by 8.5%, 25.0%, and 15.2% in the shallow, middle, and deep levels, respectively. The ionomics results showed that the total Sr, Mn, Fe, Th, Rb, Bi, S, Se, Pb, U, Ni, Ba content in the rhizosphere soil decreased by 0.10–1.06 times (Log2 FC), and the effective state elements increased by 0.21–2.24 times (Log2 FC), there is still a risk of metal pollution in the gangue area. Metabolomics shows that lipids and lipid molecules, organic acids, phenylpropane and polyketides are the main differential metabolites; C. korshinskii repair stimulates the circulation pathways of terpenoids, lipids, amino acids, and carbohydrates. S, Fe, Mn and lipids, organic acids, and organic oxygen compound metabolites drive Acidthiobacillus, Sulfurifustis, Deferrobacterium, Pseudomonas and Sphingomonas to become dominant strains, regulates element metabolism and accelerates the process of environmental restoration.

The soil ecological health risks and toxic effects of coal gangue accumulation were examined after 10 years of elm/poplar phytoremediation. The changes in soil enzyme activities, ionome metabolism, and microbial community structure were analyzed at shallow (5–15 cm), intermediate (25–35 cm), and deep (45–55 cm) soil depths. Soil acid phosphatase activity in the restoration area increased significantly by 4.36–7.18 fold (p < 0.05). Soil concentrations of the metal ions Cu, Pb, Ni, Co, Bi, U, and Th were significantly reduced, as were concentrations of the non-metallic element S. The repair effect was shallow > middle > deep. The soil community structure, determined by 16S diversity results, was changed significantly in the restoration area, and the abundance of microorganisms increased at shallow soil depths. Altererythrobacter and Sphingomonas species were at the center of the microbial weight network in the restoration area. Redundancy analysis (RDA) showed that S and Na are important driving forces for the microbial community distributions at shallow soil depths. The KEGG function prediction indicated enhancement of the microbial function of the middle depth soil layers in the restoration area. Overall, phytoremediation enhanced the biotransformation of soil phosphorus in the coal gangue restoration area, reduced the soil content of several harmful metal elements, significantly changed the structure and function of the microbial community, and improved the overall soil ecological environment.