Study On The Adaptability Of Six Oak Species To Copper Mine Soil And The Potential Of Vegetation Restoration

Land is the material basis for human survival,and it is a non renewable resource.As a big country of mineral resources consumption,heavy metal pollution in mining area and its surrounding soil is serious.Heavy metals can enter the food chain through plants and accumulate in organisms,posing a serious threat to the natural ecosystem and human health.Phytoremediation is a novel,efficient,economic,environmentally and ecologically friendly remediation strategy,which is very suitable for remediation of large areas of contaminated land.Quercus spp.is an evergreen or deciduous tree and a rare shrub.It has the characteristics of large biomass,developed root system and strong adaptability to adversity,so it has important ecological significance.In addition,oak trees are tall and luxuriant.Some of them are bright green in summer and turn golden yellow or crimson in autumn,which are of great ornamental value in landscape configuration.Many countries regard them as ornamental trees for landscaping.In view of the potential of Quercus spp.in the remediation of heavy metal contaminated soil,and to enrich the plant materials for remediation of contaminated soil in mining area.In this study,through pot experiment,Quercus fabri,Quercus pagoda,Quercus phellos,Quercus nuttallii,Quercus acutissima and Quercus virginiana,which are commonly used in urban green space,were selected as the research objects,three treatments,control,T1 and T2,were set to explore their growth,physiological response and heavy metal accumulation and transport capacity in the heavily polluted soil(heavy pollution of Cd and Cu).By analyzing and evaluating the tolerance and remediation potential of these six Quercus species to the contaminated soil in the mining area,the tolerant Quercus species that can be used for vegetation restoration of the contaminated soil in the copper mine area were selected,which can provide reference for the selection of landscape tree species in the mining area.The main results are as follows:(1)The results showed that the six Quercus species had no toxic death phenomenon in the high level of heavy metal pollution soil,and could maintain normal growth.High concentration of heavy metal pollution significantly reduced the biomass of Quercus fabri and Quercus phellos,but had no significant effect on the biomass of Quercus acutissima and Quercus virginiana.The biomass of Quercus nuttallii increased compared with the control.Six Quercus species showed different tolerance levels to contaminated soil in mining area.Quercus nuttallii had the highest tolerance index,and Quercus fabri had the lowest tolerance index.(2)Heavy metal pollution(T2 treatment)significantly reduced the photosynthetic parameters of six Quercus species,and the variation trend of leaf stomatal conductance and intercellular CO2 concentration was similar,indicating that the decline of photosynthetic capacity was the stomatal limitation.The cat activity in leaves of Quercus fabri,Quercus nuttallii and Quercus virginiana was higher than that of other Quercus species,which indicated that these three Quercus species had good resistance to heavy metal pollution and could well resist the damage caused by heavy metal.(3)In the heavy metal contaminated soil,there was no significant difference in the carbon concentrations in the leaves,stems and roots of the six species,indicating that heavy metals had no effect on the carbon accumulation capacity of the oak trees;the utilization efficiency of mineral nutrients and the synthesis ability of dry matter of the six Quercus species were strong,and their growth was mainly limited by nitrogen.High concentrations of heavy metals increased Ca content in leaves of Q.fabri,Q.nuttallii and Q.acutissima;heavy metals increased Fe content in stems and roots of Q.fabri,Q.phyllos,Q.nuttallii and Q.virginiana;heavy metals increased K content in aboveground parts of Q.pagoda,Q.phyllos and Q.virginiana,indicating that Quercus may reduce the toxicity of toxic heavy metal ions by adjusting the content of mineral elements.(4)The bioaccumulation and transport coefficients of Cd and Cu in T1 and T2 treatments were less than 1,while the bioaccumulation and transport coefficients of Zn were less than 1 and 1.6～4.08,respectively.The order of fuzzy membership function values of phytoremediation potential from high to low was Quercus virginiana>Quercus nuttallii>Quercus phellos>Quercus pagoda>Quercus acutissima>Quercus fabri.(5)According to the results of biomass,tolerance index and membership degree,Quercus nuttallii and Quercus virginiana have great potential for phytoremediation,which can be used as reference materials for afforestation and ecological restoration in mining area,and enrich the ecological landscape structure.