| The effect of mine ecological restoration mainly depends on the success of the reconstruction of the vegetation community in waste sites.Most domestic researches currently focus on species selection and plant growth environment improvement,and the research on the mechanism of plant rhizosphere effect on soil improvement in waste sites is not systematic and in-depth.In this paper,the rhizosphere soil biochemical factors,heavy metal content and microbial diversity of dominant plants(Robinia pseudoacacia and Indigofera pseudotinctoria)at different restoration ages in Jiujiang copper mine dump in Jiangxi were determined using space instead of time.In order to provide ideas for ecological restoration of waste mine sites in this area,the change rule and correlation of each index were analyzed.The main conclusions are as follows:(1)The analysis of soil factors in the rhizosphere of dominant plants through laboratory experiments showed that: soil biochemical factors fluctuated seasonally,soil enzyme activities were related to vegetation coverage and plant species.The total and available content of Cu was significantly different between restoration years,and the Cu content of the remediation plots in 2018 was the highest.This trend does not represent the effectiveness of the ecological remediation and should be related to the high background of the sample sites.Therefore,when evaluating the ecological remediation effectiveness of metal mines,the analysis of trends in total heavy metals and effective state content alone cannot indicate the effectiveness of ecological remediation,but should focus more on soil biochemical processes.(2)The high-throughput sequencing was used to analyze the diversity of bacterial communities in the rhizosphere soil of dominant plants.The results showed that the dominant bacteria were Proteobacteria,Acidobacteria,and Actinobacteria and so on.With seasonal changes,the magnitude of the α diversity indices were in the following order: Ace and Chao1 indices: December > September > April > June;Shannon index:December ≥ September ≥ April > June.The order of magnitude of the α diversity indices under different restoration years was: Restoration site in 2016≥ Restoration site in 2015 ≥ Restoration site in 2018 > Natural restoration site > Unrestored site in2020(Ace index and Chao1 index).With the increase of restoration years,the soil bacterial community richness generally tended to increase under the action of surface vegetation,and the bacterial communities became more convergent.In addition,the bacterial community diversity showed some fluctuation with seasonal changes among the sample sites.(3)The data of the restoration site in 2016 and 2018 were selected to analyze the influence of restoration years and plant species on soil factors.The results showed that there were highly significant positive correlations among soil p H,DOC,TC,IC,invertase and urease(P < 0.001).There were highly significant positive correlations among the total and available state content and bioavailability of heavy metals Cu and Zn(P<0.001).There was a significant positive correlation(P < 0.001)between the indicators of soil biochemical factors(p H,DOC,TC,IC,invertase and urease)and the indicators of soil heavy metals(total,effective state content and bioavailability of Cu and Zn)(P < 0.01).With the increase of remediation years,soil p H value increased,DOC,TC,IC contents increased,while heavy metal contents decreased.Seasonal changes and plant species had little effect on soil nutrients and heavy metal content.(4)The data of the restoration plots in 2016 and 2018 were selected to analyze the influence of restoration years and plant species on the soil microbial community.The results showed that: the Chao1,Ace,and Shannon indices first decreased and then increased with the seasonal changes,and the values of each index were minimum in June.There was a significant positive correlation between Chao1,Ace and Shannon indices(P<0.001).There was no significant correlation between restoration years,plant species and soil microbial α diversity.With increasing seasons,at the pre-mid and late stages of plant growth,the α diversity of the rhizosphere soil bacterial community increased.Soil microorganisms improved soil nutrients by secreting enzymes and extracellular substances.(5)RDA analysis showed that: Proteobacteria,Firmicutes,Nitrospirae,Patescibacteria,etc.were positively correlated with heavy metal,while negatively correlated with soil p H,DOC and urease activity.Acidobacteria,Gemmatimonadetes,Planctomycetes and Verrucomicrobia were negatively correlated with heavy metal,and positively correlated with soil p H,DOC,TC,and urease activity.As the remediation time increased,soil heavy metal content decreased,soil nutrient levels increased,soil microbial α diversity increased,and the relative abundance of bacteria with low resistance to heavy metals such as Gemmatimonadetes,Planctomycetes and Acidobacteria increased. |
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