| Since the construction of the nationwide economic development,the increasing exploitation of coal resources has led to a series of ecological problems such as the reduction of biodiversity,topsoil sand erosion and a vicious cycle of soil erosion in typical grasslands,which were already in an ecologically fragile state.As the producers of the ecosystem,plants play a decisive role in the ecological restoration of the above-mentioned degraded mining areas,and in the restoration process,they interact with the ecosystem to fundamentally improve the ecological environment of the mine dumps.In this thesis,the vegetation and soils of the Baiyinhua open-pit mine,located in the hinterland of the Xilinguole grasslands,were studied for different restoration years,and the dynamics of the plant community,soil physicochemical properties and heavy metal content in the restored areas were investigated for 3-5 years.Analysis of the correlation between plant community composition and soil physicochemical properties,plant community succession patterns and heavy metal contamination of mine dumps in the remediation area.It aims to provide theoretical support and reference for the ecological restoration of other alpine typical grassland open-pit mines.The results of the study are as follows:(1)Compared with grasslands,the number of plant species in the ecologically restored areas of drainage sites with 3-5 years of restoration is significantly lower than in the former,and the main plant species in the restored areas are more leguminous than in the former.The flora of both grassland and restoration areas is dominated by the coexistence of dominant,subdominant and associated species,with few occasional species.Both plant communities have become dominated by perennial herbaceous plants,and the ratio of perennial herbs to the total number of species in the restored area tends to increase with the number of years of restoration.(2)The organic matter content,total phosphorus and organic matter of the soil in the restored area all show a tendency to increase with the number of years of restoration,but the organic matter content increases more slowly;the opposite trend exists for the total potassium content of the soil.(3)The six heavy metals of arsenic,cadmium,copper,lead,mercury and nickel in the three major ecological restoration areas of the North,South and East drainage sites are all in a non-contaminated state.Anthropogenic coal mining activities can increase soil heavy metal levels.(4)Plant community cover and various biomass were significantly negatively correlated with soil bulk,positively correlated with other soil physical and chemical properties,and highly correlated with soil organic matter content,total phosphorus,total nitrogen and effective phosphorus content.(5)Soil total nitrogen,total potassium,effective phosphorus content and field water holding capacity have a major impact on the ecological restoration of drainage sites.Overall the effectiveness of restoration of drainage sites is increasing year on year,and there is a general preference for platform restoration over slope restoration.At 3-5 years of restoration of the Xilingol grassland opencast mine drainage site,the physical and chemical properties of the soil have not been improved to a level suitable for plant growth and establishment.Among these,soil capacity,field water holding capacity,total nitrogen,total potassium and fast-acting potassium content play a limiting role in plant rooting growth,alpine tolerance and other factors affecting vegetation establishment at the beginning of succession.Therefore,the initial stage of ecological restoration should consider cutting slopes,establishing a certain degree of soil and water conservation engineering measures and increasing the proportion of leguminous plants planting.The mitigation of soil water and nutrient losses should be accompanied by a particular increase in total soil nitrogen content to promote a synergistic evolution of the ecological restoration system. |
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