Herbaceous Plant Community Structure In A Typical Lead And Zinc Waste Site In Hezhang County And Soil Environment Interpretation

Northwest Guizhou is arenowned gathering and distributing place of earth-process zinc smelting in our country.Many artificial lead and zinc smelting activities are distributed in northwest Guizhou Hezhang and Weining areas.Due to the extensive and simple earth-process smelting process and low recovery rate of metal elements,a large number of other heavy metal elements（Pb,Cu,Cd,etc.）with ore companions are retained in smelting waste slag.The residual heavy metals in the waste slag are easy to migrate to the surrounding aquatic and agricultural ecosystems through surface runoff and wind diffusion,thus causing serious threat and harm to the agricultural ecosystems and human health in the smelting area.Phytoremediation is an important technology for the restoration of local ecological environment.However,there is a lack of systematic and comprehensive research on the relationship between plant community structure and soil nutrient and heavy metal content in lead-zinc waste site.Understanding the relationship between plant community structure and soil environment in lead-zinc mine waste site is the key basis of phytoremediation technology.In this study,the typical lead-zinc waste site in Hezhang County of Guizhou Province was taken as the research area.Through field investigation and indoor analysis,the community structure and species composition of herbaceous plants in lead-zinc waste site and its surrounding areas were systematically studied,and the distribution of soil nutrients and heavy metals content was quantitatively analyzed by multivariate statistical methods.The key soil factors affecting the plant community structure and species composition in the study area were identified in order to provide theoretical basis for vegetation restoration and ecological reconstruction in the typical lead-zinc waste site in northwest Guizhou.The main conclusions are as follows:（1）The quantitative characteristics,species diversity and community structure of dominant herb communities in lead-zinc mine waste site in northwest Guizhou were investigated.A total of 98 samples were investigated in slag heap,and 12,535 herbs were found,belonging to 14 families,18 genera and 36 species.Eragrostis ferruginea,Setaria viridis,Panicum psilopodium,Sporobolus fertilis,Eleusine indica,Cynodon dactylon,Axonopus compressus,Imperata cylindrica,Oplismenus undulatifolius and other Gramineae are the dominant species.A total of 98 quadrat squares were investigated in the surrounding area,with 13642 herb plants belonging to 90 species and 52 genera of 41 families,Artemisia argyi of Compositae,Polygonum nepalense and Polygonum capitatum of Polygonaceae are dominant species in surrounding areas.In addition,the species diversity of herbaceous plants in the surrounding area was much higher than that in slag heap,and the species composition was significantly different.（2）Common species niche and interspecific association of the top 16 dominant herbaceous species in slag heap and its surrounding areas.Make a comparative analysis.The niche widths of the top 16 dominant herbaceous plants ranged from 1.85 to 30.40.Eragrostis ferruginea,Setaria viridis,Panicum psilopodium,Sporobolus fertilis,Eleusine indica has relatively high important values and Niche width.The niche width of 16 dominant herbaceous plants in the surrounding area ranged from 1.39 to 20.03,Artemisia argyi,Eleusine indica,Selaginella pulvinat,Oplismenus undulatifolius,Imperata cylindrica has relatively high important values and Niche width.In general,the important value and niche width of the gramineae such as Eragrostis ferruginea,Setaria viridis,Panicum psilopodium,Sporobolus fertilis,Eleusine indica and Artemisia argyi were higher.In the slag heap and the surrounding area,there were 120pairs of gramineous plants,such as pterygium,setaria,lepidophora,rat tail millet and cowweed,and the ecological niche overlap was high.There were 80 pairs of negative correlation species,accounting for 66.67%of the total logarithm.There were 84 pairs of negative correlated species in the surrounding area,accounting for 70.00%of the total logarithm.The common species of dominant herbaceous plants in slag heap and surrounding areas showed significant positive association,but the species pairs were mainly negative association,indicating that the plant community in slag heap showed progressive succession on the whole,but the succession process was slow and still in the early stage of succession.（3）Based on the classical power function law,the distribution of herbaceous vegetation species and the overall spatial distribution of the community in slag heap and surrounding area were studied.The results showed that the community in slag heap and surrounding area had strong spatial heterogeneity,and the distribution of community species was consistent with the power function law.The spatial heterogeneity index（δc）of slag heap（0.342）was higher than that of the surrounding area（0.323）,and the overall spatial heterogeneity of the herb community of slag heap was higher than that of the surrounding area.（4）The average contents of Zn,Cu,Cr and Pd in the whole waste slag field are relatively high,which are 272.555 mg·kg^-1,207.693 mg·kg^-1,174.076 mg·kg^-1and 74.569mg·kg^-1,respectively,and the contents of these metals far exceed the soil background values of Guizhou Province,indicating that the mining area is seriously polluted by heavy metals.The gramineous plants,such as Eragrostis ferruginea,Setaria viridis,Panicum psilopodium,Sporobolus fertilis,Eleusine indica,are widely distributed,indicating that gramineous plants have strong adaptability in lead-zinc mining areas.In general,heavy metals and nutrients in lead-zinc waste slag field jointly affect the distribution of herbaceous plants.Among them,heavy metals Cu,Zn and Pd in soil have a greater influence,while nutrients TN,p H and OM have a greater influence.In this study,although the lead-zinc slag heap has been deposited for more than100 years,there are still problems such as high heavy metal content,poor soil fertility,low species diversity,slow vegetation succession and still in the early stage of succession.In the process of ecological management,it is recommended to consider the ecologically adaptable and widely distributed gramineous plants,such as Artemisia argyi,Eleusine indica,Selaginella pulvinat,Oplismenus undulatifolius,Imperata cylindrica,etc.as the pioneer plants.When the ecological environment is improved,it can be supplemented with Artemisia argyi,Polygonum capitatum and Polygonum nepalense Meisn.And plants adapted to acidic environment to accelerate vegetation restoration.In the middle stage of succession,the vegetation restoration model can be built by planting Buddleja davidii and Viburnum dilatatum to promote vegetation restoration in lead-zinc mining areas,increase species composition and diversity,accelerate the succession process,and improve the stability of vegetation community.