| Shenfu-Dongsheng coal mining area located in arid or semi-arid region, the large-scale and intensive exploitation of coal contributied to huge social and economy development, meanwhile brought a series of ecological and environmental problems, appears ground subsidence and surface crack, deteriorates soil structure destroyed, soil moisture and nutrients, plant roots and vegetation, microbial diversity, which urgently needed to be solved. In order to discuss the self-repair capability of microenvironment in plant rhizosphere by coal mining subsidence and different factors in ground subsidence areas, this paper studied the effect of the rhizosphere ecological variables in the coal mining progress; in order to understand the diversity of AM fungi in plant roots after two years self-healing, 454 Pyrosequencing technology was applicated. those two studies showed that the plant rhizosphere microecological could be self-healing, but the speed was slow. In order to accelerate ecological restoration, this paper studied the effect of different microbial combination on ecological restoration on coal mining subsidence. For the reason of ecological self-healing and microbial reclamation of coal mining areas restricted by water and nutrients, this paper studied the effects of AM fungi combined with straw mulch under drought stress from simulation experiments. The experiment carried out above provided a scientific theoretical basis and technical support for the ecological reclamation and ecological reconstruction in the western mining area. The main conclusions are as follows:1. Microorganisms and enzyme activities in the rhizosphere of plant were affected significantly by the ground subsidence, surface crack, slope direction, slope position, plant species and specifications, but the microbial community structure were retatively stable, in terms of quality, bacteria > actinomycetes > fungi. After one year of coal mining self-healing, the quantity of microbe in the rhizosphere of Salix psammophila in ground subsidence were decreased, the numbers of microbe in the rhizosphere of Artemisia sphaerocephala passed by the surface crack increased significantly; the number of actinomycetes in rhizosphere of Artemisia sphaerocephala planted in windward slope and leeward slope increased significantly, but the number of bacteria and fungi was reduced, all kinds of microbe in leeward slope showed much more than windward slope; among different plants, the largest number of bacteria and fungi appeared in the rhizosphere of Populus, the largest number of actinomycetes appeared in the rhizosphere of Poa pratensis; among different specifications of Populus, the large Populus had the largest number of all kinds of microorganisms. the phosphatase activity in the subsidence area was significantly higher than the non-subsidence area, Artemisia sphaerocephala passed by cracks was higher than not passed by the crack, the phosphatase in the rhizosphere of midum Populus and Artemisia sphaerocephala in windward slope significantly decreased,phosphatase activity in the rhizosphere of Poa pratensis increased significantly; the phosphatase activity and urease activity in the rhizosphere of Artemisia sphaerocephala in leeward slope, top and bottom of windward slope in coal mining increased significantly; in terms of specifications of Populus, phosphatase activity and urease activity of the large Populus significantly increased.2. After one year ecological self-healing, soil pH and electrical conductivity in the rhizosphere of plant significant reduced when compared with before coal mining, in terms of reducing the effect of soil alkaline, leeward slope got well effect than windward slope. In terms of phosphorus, phosphorus content after one year in rhizosphere of Artemisia sphaerocephala passed through by cracks was higher than mining process; available phosphorus content in rhizosphere of Salix psammophila and Artemisia sphaerocephala in windward slope of ground subsidence significantly reduced, the content of one year later far back to before coal mining levels, among them, the windward slope recovered faster than the leeward slope; phosphorus content of Populus and Poa pratensis increased by ground subsidence, the self-healing effect of Populus are as follows: large Populus > medium Populus > small Populus. One year of coal mining later, the mycorrhizal infection rate of Salix psammophila in subsidence area and Artemisia sphaerocephala passed by cracks was significantly higher than before coal mining, infection rate of leeward slope was higher than the top of windward slope, the least value appeared in medium of windward slope, the infection rate of large Populus and Poa pratensis significantly increased and medium Populus and small Populus significantly decreased by coal mining. The hyphal density increased by coal mining, the spore density reduced by ground subsidence.3. AM fungal diversity and community composition in plant roots were impacted by coal mining subsidence, topography and host plants. In the research area, the number of OTU in the root of Salix psammophila was 19, which accounted for 51.4% of the number of AM fungi in the of rhizosphere Salix psammophila; the number of OTU in the root of Artemisia sphaerocephala was 25, which accounted for 89.3% of AM fungi numbers in the of rhizosphere Artemisia sphaerocephala; the number of OTU in the root of Caragana korshinskii was 21, which accounted for 87.5% of the number of AM fungi in the rhizosphere Caragana korshinskii. Chao abundance index reduced and Shannon diversity increased of AM fungal within the root of Salix psammophila in the ground subsidence when compared with non-subsidence region. These two areas occupied 12 OTU together, advantage family is Glomeraceae. In different slope position and slope aspect, the highest Chao abundance index and Shannon diversity appeared in the bottom of the windward slope, the similarity of community composition of AM fungi in the Artemisia sphaerocephala root from different position was much higher, and the advantage OTU of AM fungi in root of Salix psammophila from all locations was OTU6; AM fungi in the root of Artemisia sphaerocephala from all locations 100% distributed in the Glomeraceae. When copared with Artemisia sphaerocephala, Caragana korshinskii root and Salix psammophila, the highest Chao abundance index and Shannon diversity appeared in Artemisia sphaerocephala, the community composition similarity is extremely high among these three kinds of plants, among them, dominant families of AM fungi was Glomeraceae.4. The speed of ecological restoration can be accelerate after the application of microbial reclamation technology in coal mining areas. Microbial reclamation technology could improve the survival rate and increased the height and crown of Amorpha fruticosa significantly, and the average survival rate was more than 90%, the single inoculation of G.i could improved the plant survival rate best, single inoculation of G.m could promoted plant growth best. Phosphatase activity in the rhizosphere of Amorpha fruticosa in different treatment rised with the extension of reclamation time. Glomalin is an important component of soil organic carbon, which give sensitive response to soil quality change. Meanwhile, the number or bacteria, fungi, actinomycetes and total microbial, the content of phosphatase, glomalin, organic carbon, available phosphorus and nitrogen were increased by microbial reclamation technology, so the microbial reclamation technology could effectively curbed the restriction poor soil nutrient to vegetation ecological restoration in coal mining area in a certain extent. The difference of phosphatase activity in different treatments was the most obvious After 14 months, the phosphatase activity sequence was G.i > G.m > G.m+CA >G.m+G.i > CA > CK, which increased by 64%~110%. Soil pH value could reduce 0.91~1.29 unit for the reason of Amorpha fruticosa planted in coal mining areas, the inoculation treatment could obvously improved the environmental impact of alkaline stress in the short term when compared with the control. Mycorrhizal infection rate, mycorrhizal infection rate, hyphae and spores density of Amorpha fruticosa could improved significantly with the microbial reclamation technology than the control treatment, which were affected by different reclamation time and different microorganisms. As an important organ of plant, the roots play an important role in the process of absorbing moisture and nutrients. The study found that, total root length, the total projected area, total surface area, total volume and the total number of tips of Amorpha fruticosa in the inoculation treatment significantly increased compared with the control treatment. After 2 months to 11 months inoculation, the average diameter of root in inoculation treatment was bigger than the control treatment; after inoculation 14 months, the average diameter of the root inoculation treatment was lower than the control treatment.5. After two years of microbial reclamation technology applied, 76006 optimum sequences were got from 17 root samples of Amorpha fruticosa, the average sequence length was 447 bp, optimization rate of sequence was 78%, which distributed in 34 OTU. OTU number in treatment of G.m+G.i、G.i、G.m、G.m+CA、CA、CK was 13, 13, 26, 27,17 and 21 respectively, G.m+CA and G.m inoculation could increased AM fungi species diversity, promoted stability of mining ecosystem. the same OTU number among five kinds of inoculation treatment was eight, the community composition similarity was extremely high among these 5 kinds inoculation treatment. OTU6、OTU21、OTU10 and OTU28 widely distributed in more than 80% of the samples dominant families of AM fungi in each treatment was Glomeraceae, among different treatments, AM fungi of Gi, Gm, CA and CK treatment 100% distributed in Glomeraceae, AM fungi of G.m+CA、G.m+G.i treatment distributed in Glomeraceae and Diversisporaceae.6. Three kinds of water conservation measures, such as AM fungi inoculation, straw mulching and AM fungi inoculation combined with straw mulching could efficient alleviate the drought stress on plant growth. Under drought stress, the water requirement was least in treatment of AM fungi and straw mulching coordinated, 14% decreased in water than normal water supply, while increased available P. Compared with the normal water supply treatment, the biomass of maize significantly reduced by drought stress, the effect in treatment of AM fungi and straw mulching combined was better than it was in single AM fungi inoculation and straw mulching treatment. The content of available P could increased effectively in treatment of inoculation of AM fungi and straw mulching, meanwhile, the treatment of straw mulching was better than treatment of AM fungi combined with straw mulching. The inoculation of AM fungi had contribution to the mutual integration of AM fungi and plant roots, the mycorrhizal infection rate increased under drought stress condition, the treatment of AM fungi inoculation had the highest infection rate. The hyphae density reduced under drought stress, the hyphae density value reached to 3.11 m ? g-1 under normal water supply The content of leaf proline significantly increased by drought stress, the lowest value of proline in plant leaf under normal water supply. Drought stress increased the leaves and roots total nitrogen contention, drought stress increased plant leaves phosphorus concentration and decreased roots phosphorus concentration with inoculated AM fungi and straw mulching. |
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