Vegetation And Soil Properties Of Ecological Restoration In Typical Open-pit Mines Of Inner Mongolia Grassland Areas

The dump of mining area and sandstone mining area in Inner Mongolia grassland have great impacts on grassland ecological environment.For example,the vegetation is destroyed seriously,and the phenomenon of soil wind erosion and water erosion is quite commom with the coal mining activites.To solve those problems,vegetation as well as soil physical and chemical properties of artificial restoration areas,natural restoration areas and native grassland of five coal mining area were chosen in Inner Mongolia grassland(Jalainur Linglu coal mine,Huolinhe mine,Xilinhaote Shengli West No.3 open-pit mine,Heidaigou open-pit mine in Ordos City and Camel Mountain mine in Wuhai)to investigate the effects of different restoration measures on the ecological restoration of grassland mining areas.During the 2012 to 2018,the plant community and soil physical and chemical properties of Chilechuan grassland sand filed were monitored every year in August.In 2018,the plant community and soil physical and chemical properties of artificial restoration area,natural restoration area and native grassland in five coal mining areas were investigated,and the ecological restoration effect of different restoration measures on the grassland mining area was compared and analyzed.Based on the comprehensive analysis and discussion of the ecological restoration effect and the changes of plant community and soil physical and chemical properties of two different mining areas,the conclusions are shown as follows:(1)In the case of good natural basement conditions,the plant community and soil physical and chemical properties of grassland open-pit coal mine dump after natural restoration for more than 20 years are closer to the original grassland.the dominant species of the plant community under 5 years of artificial restoration were mostly artificial restoration species,and the high coverage and aboveground biomass of the plant community were higher than or close to that of the original grassland.(2)In general,the soil bulk density in the artificial restoration area was higher than that in the original grassland and natural restoration area,and the available nitrogen,available potassium and organic matter in the original grassland were higher than that in the artificial restoration area and natural restoration area.The organic matter in grassland was higher than that in native grassland in 2-3 years of artificial restoration and 20 years of natural restoration.(3)During the process of grassland ecological restoration,the ecosystem resilience and stability are closely related to the restoration years and species diversity.Especially,the ecosystem resilience is positively correlated with the plant community species diversity,and the resilience is positively correlated with the recovery time.The longer the recovery time,the stronger the stability,and the closer to the original natural community,and the stronger the correlation between the soil-vegetation indexes.(4)In the sandstone mining area,the number of species,density,diversity and resilience of the plant community increased first,then decreased and then increased with the recovery time.The community stability was positively correlated with the recovery time.The longer the recovery time was,the more stable the community was and the more native species were colonized.(5)In the sandstone mining area,soil available nitrogen,available phosphorus,available potassium and organic matter showed a trend of increasing.From 2012 to 2018,the soil organic carbon reserves in the sandstone mining area accounted for over 92.92%of the total organic carbon reserves.The soil organic carbon reserves played a dominant role in the recovery process,making it the largest carbon reservoir in the ecological recovery process.(6)The correlation analysis of the ecological restoration effect of sandstone mining area from 2012 to 2018 shows that the ecological restoration effect was ranked as 2014>2013>2012>2015>2018>2016.With the increase of the recovery time,the restoration area shows the recovery process from artificial restoration to natural succession.Overall,artificial restoration can promote the rapid improvement of grassland plant community and soil physical and chemical properties,so as to meet the requirements of ecological restoration in grassland mining areas.However,the duration of grassland plant community and soil physical and chemical properties to the original grassland will not shorten.Furthermore,the process of artificial restoration mainly includes:artificial plant community--native species invasion--native plant community;the natural recovery process mainly includes:annual and biennial plants--perennial species invasion--native plant community.However,the changing process of soil physical and chemical properties is complicated during the process of restoration.