| In this thesis,the vegetation-soil system on a reclaimed tailings dam of Jianshan Iron Mine in Shanxi was taken as the research object.Based on the field plant plot and soil sampling,the plant community composition,the relationship between dominant species,plant species diversity,soil physicochemical properties and enzyme activity changes in different revegetated periods on the reclaimed tailings dam were studied by quantitative ecology and soil biochemical analysis.The vegetation-soil system coupling relationship and ecological restoration quality of the reclaimed tailings dam were evaluated using the the vegetation-soil coupling model,and the pioneer plant species and the optimal plant combinations suitable were screened for revegetation on tailings dam.This research results will provide scientific basis and technical guidance for improving the restoration quality of vegetation-soil system on the tailings dam.The main research findings are as follows:1)The 72 quadrats of plant communities in different revegetated periods in the study area were divided into 8 communites(associations),that is,Medicago sativa + Vicia amoena,Caragana korshinskii-Phragmites communis-Artemisia capillaris,Hippophae rhamnoides-Calamagrostis gmelinii,Caragana korshinskii-Elymus dahuricus,Lespedeza daurica-Cleistogenes Squarrosa + Bothriochloa ischaemum,Agropyron desertorum + Cleistogenes squarrosa,Caragana korshinskii-Artemisia capillaris-Calamagrostis epigeios,Caragana korshinskii-Eleusine indica,which were in the initial and middle stages of ecological restoration succession by using the two-way indicator species analysis(TWINSPAN).The DCA and CCA ordination respectively reflected the gradient change of reclamation time,soil moisture matter of the reclaimed tailings dam.2)The plant species of Compositae,Leguminosae and Gramineae were dominant in vegetation communities on the reclaimed tailings dam of Jianshan iron mine.With the increase of revegetated year,the plant species diversity and evenness of different plant communities on the reclaimed tailings dam gradually increased,and the community tended to be stable.Plant species diversity index of associations dominated by Caragana korshinskii in associations IV(Caragana korshinskii-Elymus dahuricus),II(Caragana korshinskii-Phragmites communis+Artemisia capillaris)and ?(Caragana korshinskii-Eleusine indica)changed obviously.The relationship between dominant plant species indicated that there was a strong positive correlation between legumes and grasses,such as the planted Caragana korshinskii and the naturally colonized plant specie of Elymus dahuricus,the naturally colonized plant specie of Bothriochloa ischaemum and the planted Lespedeza daurica.It was suggested that the mixed plant combinations of leguminous and gramineous plants should be adopted in the process of vegetation restoration on iron tailings dam.3)With the increase of revegetated years,the soil biochemical properties have been significantly improved,and soil fertility has been gradually improved.Especially,the restoration of soil quality was particularly evident when the vegetation association was recoveried for more than 12 years.The restoration succession of plants could be roughly divided into two stages.The initial stage of restoration(?10a)was mainly affected by plant community characteristics.With the increase of revegetated years,the middle and later stage of restoration(>10a),the change of soil environment changed the characteristics of plant communities.The distribution of plant communities was greatly affected by soil properties.4)The association I(Medicago sativa + Vicia amoena)with the leguminous plants as the dominant plant species has remarkable effect on improving soil total nitrogen,available nitrogen and organic matter contents,and has the highest comprehensive vegetation evaluation index P(y)(0.6062).The ecological restoration quality of vegetation-soil system was optimal during the restoration process on the reclaimed tailings dam.It is recommended to use the mixed plant combinaions of leguminosae(such as Medicago sativa and Caragana korshinskii)and gramineae(Elymus dahuricus,Agropyron desertorum,Bothriochloa ischaemum)for future ecological restoration of iron tailings dam.5)From the long-term effect of soil quality improvement,the soil quality improvement of mixed combitions of shrub and herbaceous plants is better than that of the herbaceous plant pattern.Revegetation using this mixed combition is therefore recommended for future reclamation of abandoned iron tailings dam.6)From the results of the coupling degree Dp of soil-vegetation system,the coordination degree of vegetation-soil system was getting better with the increase of revegetated years.In the middle and later stages of vegetation restoration,the coordination degree of vegetation-soil system was in the basic coordination state.The vegetation-soil system for association IV(Caragana korshinskii-Elymus dahuricus)had the best coordination state,and their combinations could provide reference for future's ecological restoration on iron tailings dam.Our field survey found that the planted grassland in the middle and late stages of restoration showed obvious degradation.It is suggested that the scientific management of revegetation should be strengthened in the process of ecological restoration,in order to improve the ecological restoration quality and effect,and to promote the stable and self-sustaining development of vegetation-soil system on tailings dam.This study found that shrub pattern is better than that of the herbaceous plant pattern in the process of vegetation restoration on iron tailings dam,and the role of the legume(Caragana korshinskii,Medicago sativa)and grass(Elymus dahuricus,Agropyron desertorum,Bothriochloa ischaemum)plant configuration patterns is obvious.The vegetation-soil system for Caragana korshinskii-Elymus dahuricus had the best coordination state,and their combinations could provide theoretical basis and reference for future's ecological restoration on iron tailings dam. |
PDF Full Text Request