| The Shanxi-Shaanxi-Inner Mongolia region is an energy base in China,super-large in scale and rich in coal reserve.Massive opencast mining activities in the region do promote development of its economy,nevertheless they bring about a series of environmental and ecological problems,such as destruction of surface landscape,damage of vegetation,pollution of the environment,etc.In this study,soil nutrients,soil bacterial community structure and diversity of 22 kinds of treatment samples in Heidaigou eastern dump and Yongli coal mine were studied.Soil nutrients of Yongli reconstructed plots,the original landform and the new structured soils were studied.Comparison was made for differences in nutrient status and the weighted synthesis method was used to evaluate the nutrient quality of several soil types.Soil nutrients under different plant measures were compared to explore different degree of recovery and ameliorating effect among different artificial vegetation restoration measures,natural vegetation restoration measures and blank control in Heidaigou eastern dump.This study also investigated the changing rules of soil bacterial diversity and community structure as well as correlation among the samples,species and environmental factors in each sample of all treatments and different groups to evaluate the effects of different vegetation measures in Shanxi-Shaanxi-Inner Mongolia mine dump region,which can provide theoretical direction and reference for later screening of reclamation vegetation and soil restoration.The results are as follows: 1)After 19 years of ecological restoration for Heidaigou eastern dump,comparing with the soil nutrient in new dump,different types of artificial vegetation and natural vegetation had different degrees of ameliorating effect on soil nutrients,except for the soil total nitrogen content in natural grassland and ammonium-nitrogen content in mixed grass in the 10~20 cm soil layer.Soil nutrient in all six kinds of artificial vegetation did not recover to the level of the soil nutrient in the natural sea-buckthorn forest.The nutrient content of natural grassland was not high,and other artificial vegetation types were superior to the soil nutrient level in natural grassland,except for the scotch pine forest and seabuckthorn forest.The soil nutrient level of artificial seabuckthorn forest was far below the nutrient level of the natural seabuckthorn forest,indicating that the duration of restoration of vegetation in the mining area had a significant impact on the ecological restoration.2)Among several kinds of artificial vegetation,shrubs and grass mixtures had the most significant ameliorating effect,soil nutrients in black locust forest were increased significantly.Various grasses mixtures and amorpha fruticosa linn forest had higher soil nutrient recovery degree,and scotch pine forest had poorer nutrient recovery effect on mining dump.3)Soils under three different amelioration modes were obviously higher than original landform soil in content of soil organic carbon,available phosphorus and nitrate-nitrogen,and almost as high as original landform soil in content of soil ammonium-nitrogen,but still lower in content of soil total nitrogen.Soil amelioration mode of mixing weathered coal has the highest soil nutrient quality,followed by the mode of mixing fieldspathic sandstone,and the soil nutrient quality of sandy loess soil is higher than the original landform soil,while the quality of the blank control is the worst,showing three amelioration modes all have some positive effects on soil nutrients.4)The community diversity of Heidaigou eastern dump was higher than that in the Yongli coal mine dump,and Yongli's six reconstructed plots had different community diversity.Yongli artificial vegetation group respectively had significant variation with Heidaigou artificial vegetation group and Yongli reconstructed group in the community diversity.The dominant bacteria in two mining dump was Acidobacteria,Chloroflexi,Bacteroidetes,Actinobacteria,Proteobacteria,among all species,Cyanobacteria's abundance was the lowest.Microbes were mostly suitable for lower nutrient content environment,and they participated in the cycle of carbon,nitrogen,phosphorus and other materials and had nutrients fixation effect.Microbial biomass carbon had maximum correlation with soil microbial community and species distribution among seven environmental factors in the test,followed by soil organic carbon,ammonium-nitrogen,available phosphorus,total nitrogen and microbial biomass nitrogen,nitrate-nitrogen.The Yongli control was quite different from other samples,and it was least affected by environmental factors.Therefore,with the increase of reclamation time,the mining area has a significant improvement effect on nutrient condition and microbial community.In the construction of vegetation and ecological restoration of the mining area,black locust is a very suitable tree species,so we can give preference to leguminous deciduous shrubs dominated by Amorpha fruticosa Linn and seabuckthorn,as well as leguminous herbaceous plants,such as astragalus adsurgens pall and alfalfa,and appropriate mixed-vegetation configuration patterns should be added under the trees and shrubs,some grasses such as Stipa bracteata should be planted.We can give full play to local resource advantages and use weathered coal widely for soil texture improvement,which can as well improve the ecological environment as achieve certain economic benefits. |
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