Study On Ecological Restoration Of Limestone Open Pit Mine In Northwest Sichuan

Limestone is widely distributed in Northwest Sichuan.Affected by open-pit mining activities,surface soil stripping,vegetation damage,soil wind erosion and water erosion have occurred in the limestone mining area,seriously affecting the landscape and ecological environment of the mining area.Firstly,through literature research and case analysis,this paper systematically analyzes the characteristics of limestone mines and the impact of mining activities on ecology.Based on the investigation and analysis of the basic data,the research direction and content are determined.Then,the field investigation of wulongdong limestone open pit mine in Jiangyou City was carried out.According to the soil conditions,the study area was divided into excavation slope area,mine transportation road area and original vegetation growth area.Sampling investigation and experimental analysis（p H,SOM,TN,AP,AK）were carried out for each type of regional soil.Based on the experimental results,the soil quality of each region was evaluated.Combined with the experimental analysis results of soil indicators,soil quality evaluation results and the special habitat of limestone mining area,the grass shrub arbor rattan plants suitable for planting in limestone mining area were optimized.The vegetation restoration project of typical limestone open-pit mine was selected to investigate the restoration effect,and the scientificity of the corresponding research was tested.The main results are as follows:（1）Soil samples were collected from 11 areas in Wulongdong mining area,including the excavation slope area（s1-1-s2-3）affected by mining activities,the guest soil area（R1,R2,R3）of the mining road,and the original vegetation growth area（O1,O2）not affected by mining activities,and the p H,SOM,TN,AP,AK and other indicators of the soil samples were measured.The results show that the soil in the road guest soil area（R）and excavated slope area（s）is neutral（7.0-7.5）and alkaline（7.5-8.0）,and the original vegetation growth area is acidic to slightly acidic（5.0-5.8）.The content of soil organic matter in all areas is lower than 20g/kg.The contents of TN,AP and AK in the soil of zone R and o are within the range of grade 4,and that of zone s is within the range of grade 5.（2）Based on the experimental results,the fuzzy mathematics principle is used to comprehensively evaluate the soil in the whole region,and the membership degree and weight analysis of each index are carried out.The comprehensive index results show that the soil quality in the whole region is at a low level（0.27-0.383）.Combined with the evaluation results and the ecological characteristics of limestone area,the AHP analytic hierarchy process is used to construct the vegetation optimization model of limestone mining area.After analysis,the priority of various types of plants is as follows:Herbs: tall fescue > White Clover > corolla > alfalfa > bermudagrass;Shrubs: Amorpha fruticosa > Euonymus japonicus > Ligustrum lucidum > Jasmine >Robinia pseudoacacia.（3）The vegetation reconstruction project of Hanjiagou open pit mine within the visual range of Wulongdong open pit mine is investigated.The investigation results show that tall fescue,Ligustrum lucidum and other plants in the optimization results have a high survival rate and good growth.However,the mortality rate of arbor,Cinnamomum camphora,Michelia and other plants bred in the mine is higher.The results showed that the content of organic matter in the soil of shrub Ligustrum lucidum was higher（grade 3）than that of other vegetation（grade 4）.Infrared analysis shows that all soils contain clay minerals and quartz in varying degrees.