Evaluation On Soil Resilience Of Dumping Site In Arid And Semi-arid Open-pit Mine

The restoration of mine soil structure and function is a key factor controlling the status of most terrestrial ecosystems.Soil resilience provides an indicator of ecosystem stability and can be used as a measure of soil management sustainability.In this study,Heidaigou open-pit mine in Inner Mongolia was selected as the research area,and the soil restoration of the dump site was taken as the research object.Combining field investigation and field data analysis,the characteristics of the soil restoration of the dump site and the key factors that caused the degradation of the soil ecosystem were analyzed.Quantitative evaluation system of soil resilience of open-pit mine dump with principal component analysis method and structural equation model method.The main findings are as follows:(1)Dump as a degraded soil ecosystem,the soil structure and function of the dump are directly degraded due to the displacement of the soil material.Compared with the original landform soil,the reclamation soil bulk density of the dump is larger.The soil nutrients are degraded,the soil fertility level is low,the soil alkaline nitrogen content and organic matter content are superficial,and the roots of the plant use nutrients to a low degree.Soil biodiversity decreased and activity decreased.The chemical and biological properties of the soil are significantly different in the dumps of different years,that is,their nature changes are more sensitive at different recovery stages.The vegetation restoration and soil restoration of the waste dump are synergistic changes.Through the artificial soil improvement technology,the physical structure of the soil is improved,the chemical indicators such as cation exchange capacity and electrical conductivity are improved,and the biological activity of the soil is also significantly improved.(2)The quantitative assessment of soil resilience is divided into four dimensions: soil structural stability,soil water retention capacity,soil fertilizer retention capacity,and soil biological activity.The structural path model was used to calculate the influencing path coefficients.The results showed that the factors of fertilizer retention,water retention and soil biological activity had a positive impact on the soil resilience.The impact coefficients were 0.66,0.54 and 0.37,respectively.The force has a positive effect,the coefficient of influence is-0.33,and the structural equation model has a good fit to explain the soil resilience.(3)The soil resilience index(RI)is between-0.2858 and 0.0433,with an average value of-0.629.The RI value of the reclamation dump was the largest in 1995,and the RI value of the reclamation dump was significantly lower in 2015 than in other years.As the recovery time is longer,the recovery ability of soil structure and function is stronger.The whole research area is divided into 5 different levels of resilience,the North Dump with a reclamation time of 24 years,and the East Dump with a reclamation time of 11 years have higher levels of resilience,and the shortest reclamation time is 4 years.The bay dump site has the lowest grade.The plots of several reclamation vegetation allocation models of Hippophae rhamnoides Linn.,Robinia pseudoacacia Linn.,Armeniaca sibirica(Linn.)Lam + Pinus tabuliformis Carr.,Populus Linn.+ Hippophae rhamnoides Linn.were evaluated as the highest resilience grades.(5)Soil fertility retention capacity,soil biological activity are associated with reclamation time and vegetation type.By improving the stability of the soil structure,selecting artificial control methods for planting Hippophae rhamnoides Linn.,Robinia pseudoacacia Linn.,Armeniaca sibirica(Linn.)Lam + Pinus tabuliformis Carr.and other plant types,the direction and speed of the succession of the dumping ecosystem can be changed to a certain extent,and the recovery period can be shortened to achieve the purpose of improving soil resilience.There are 37 figures,29 tables and 109 reference in the thesis.