| The environmental governance of metal mine wasteland has always been an important environmental problem faced by China and even the world,especially how to develop a comprehensive solution of low cost and no maintenance for a large number of mine wasteland left over from history,which has always been an important scientific and technological problem in related fields.From the perspective of restoration ecology,plant community reconstruction is considered to be an effective means to reduce soil heavy metal pollution in mining areas and comprehensively restore the mine environment.However,how to follow the law of natural succession according to the succession process of plant communities in wastelands in mining areas,and find an entry point for artificially promoting vegetation renewal to drive and accelerate the succession process of plant communities,there is still a lack of systematic and comprehensive research.To this end,this study took the wasteland of Huize in Northeast Yunnan as the survey and research object,comprehensively studied the environmental characteristics of different vegetation succession stages in the wasteland of the mining area,explained the changes of community and its plant species diversity and soil physicochemical properties,compared soil environmental factors with plant characteristic values using redundancy analysis,preliminarily revealed the characteristic changes of the environment during the succession of plant communities in the wasteland of the mining area,and accumulated data for further exploring the key factors driving the succession of plant communities in the mining area.The findings are as follows:(1)The level of biodiversity of wasteland in mining areas has improved significantly with the succession of plant communities.At the beginning of the natural succession of mine wasteland,the plant species composition was single,mainly annual herbaceous plants,and the vegetation coverage was low,a large area of land was exposed;with the occurrence of the natural succession process of vegetation,the number of plant species on the wasteland in the mining area and the nutrient content in the plant body increased significantly,and the species composition of the plant community gradually became more complex and diverse.A total of 66 plants from 34 families and 58 genera were found in the sample site,of which 42 species of plants in Asteraceae,Rosaceae and Lamiaceae,accounting for about 59% of the total number of plants in the mine,showed high adaptability in the abandoned habitat of the mining area,and were pioneer plants in the ecological succession of heavy metal composite pollution areas;compared with the early stage of community succession,the species richness index increased by about 3 times,and the species diversity index increased by nearly 2times.The uniformity index increased by about 1.5 times.(2)The soil trophic conditions of the wasteland in the mining area have been significantly improved with the succession of plant communities.At the beginning of the succession of wasteland in the mining area,the soil moisture content and porosity were only 4.40% and 33.96%,respectively,which affected the soil moisture,air and fertility conditions,which were not conducive to the colonization and growth of plants;with the succession of plant communities,compared with the early stage of succession,the soil moisture content increased to 8.60%,the porosity increased by 21%,the soil organic matter,nitrogen,phosphorus and potassium nutrient content were 9,13,18 and3 times of the initial content of the wasteland,respectively,and the physical and chemical properties and nutritional status of the soil were significantly changed;in the later stage of vegetation succession,Soil quality is close to the level of the reference area of natural forest.(3)The pollution of heavy metals in the wasteland of the mining area has decreased significantly with the succession of plant communities.In the early stage of the succession of wasteland in mining areas,soil pollution was serious,of which heavy metal Pb and Zn pollution were the most prominent,and the content and effectiveness of heavy metals in the soil were reduced in the process of vegetation succession,the comprehensive soil pollution index was reduced from 36.49 to 5.43,and the soil environmental quality was restored to a higher level;correlation analysis showed that heavy metals Zn and Pb on the wasteland belonged to homologous or composite pollutants,which appeared together in metal mining areas.(4)The redundant analysis of plant community characteristics and soil properties showed that the two soil physical indicators of porosity and bulk density,the three soil chemical indicators of p H,total phosphorus and available phosphorus,total potassium and available potassium content,and the content levels of lead and zinc and its available component of two types of heavy metal pollutants played a key driving role in the succession of plant communities.The discussion concluded that it is feasible to restore the damaged mine environment by using the natural succession of mine wasteland,and that grasping the main drivers affecting succession at different stages,supplemented by active intervention by humans,can promote the rate of succession of plant communities and optimize the succession process. |
