Effects Of Baiyinhua Coal Mine On Mosses And Microbial Community Structure In Biological Soil Crusts Under Typical Steppe Vegetation

The arid and semi-arid steppe vegetation in Inner Mongolia is characterized by perennial grasses and small shrubs are inlaid with biological soil crust（BSCs）patches.BSCs are the most important surface biological mulch in typical steppe,and play an important role in stabilizing the surface environment,preventing in-situ sand generation to cut off sandstorm sources,promoting the reproduction and survival of soil microorganisms and microfauna to improve soil material transformation.Their existence is one of the important indicators of soil and ecosystem health in this region.In recent years,the pollution of dust and heavy metals caused by open-pit mining of coal mines in grassland areas has destroyed the natural balance between soil nutrients and vegetation growth,resulting in serious wind erosion and desertification and low vegetation coverage.Based on the diversity of the importance and functions of BSCs in soil desertification management and ecological restoration in arid grassland,this study focused on the mosses crusts around Baiyinhua mining area and North dump in typical steppe area were taken as research objects,investigation of crust of moss plant community structure and crust soil bacteria,fungi,arbuscular mycorrhizal fungi（AM fungi）community structure characteristics,the correlation between the physicochemical properties and enzyme activity of crusted soil and the coverage of mosses and microbial composition was analyzed,and the influence of mining area on the structure of mosses and microbial community under different distance gradient was discussed.The main research results are as follows:1.A total of 5 species,4 genera and 2 families of mosses on the crust were found in the study area,they were Phascum cuspidatum var.schreberianum,Bryum argenteum,Bryum dichotomum,Pterygoneurum kozlovii and Weissia controversa.With the increase of the distance from the main mine,the coverage of mosses decreased gradually（34%-13%）,which was negatively correlated with the coverage of vascular plants.The coverage of mosses around the north dump was not affected by the distance gradient and remained at 5-6%,which was close to the coverage under the natural vegetation of typical steppe（5.33%）.2.There were significant differences in Beta diversity of bacteria,fungi and AM fungi in moss crusts at different distances gradient around the main mine.The dominant bacterial groups were acidobacteria,Proteobacteria,Bacteroidetes and verrucomicrophyla.With the increase of distance,the relative abundance of acidobacteria in grazing area gradually increased,while the relative abundance of Verrucomicrobia in enclosure area gradually decreased.The dominant fungal groups were Ascomycota,Basidiomycota and Glomeromycota.With the increase of distance gradient,the relative abundance of Ascomycota increased and Basidiomycota decreased in grazing areas.The community composition of fungi（including AM fungi）was significantly different at genus and species level.3.There were significant differences in community structure Alpha diversity of bacteria and AM fungi,and community structure Beta diversity of bacteria and fungi（including AM fungi）in mosses at different distances gradient around the north dump.The community composition of bacteria and fungi at phylum level was the same as that in the sampling points around the main mine.With the increase of distance,the richness and diversity of bacterial and fungal communities gradually decreased,and the relative abundance of Acidobacteria in bacteria increased gradually,while the relative abundance of Bacteroidetes and Planctomycetes decreased gradually.The relative abundance of Basidiomycota in fungi increased gradually,while Ascomycota decreased gradually.At the genus level,AM fungi were dominated by Glomus.4.Coal mining resulted in significant changes of some nutrient contents and enzyme activities in soils with moss crusts around the main mine and north dump.With the increase of distance,the contents of pH,total nitrogen,nitrate nitrogen,available potassium and the activities of alkaline phosphatase,urease and dehydrogenase in the moss crusts soil of the main mine enclosure area increased significantly,while the content of available phosphorus decreased significantly.PH and the content of ammonium nitrogen in moss crusts soil of the main mine grazing area decreased significantly.PH,content of ammonium nitrogen and available phosphorus,activities of polyphenol oxidase,alkaline phosphatase and sucrase in moss crusts soil around the north dump were significantly increased.The content of available potassium was significantly reduced.5.The coverage of mosses on the crusts was extremely significant positively correlated with nitrate nitrogen,significant negatively correlated with total potassium,available potassium and sucrase,and extremely significant negatively correlated with pH and urease.Correlation analysis results showed that pH,total nitrogen,ammonium nitrogen,available phosphorus and alkaline phosphatase significantly affected the bacterial community composition in moss crusts of the study area.PH,ammonium nitrogen,total phosphorus and urease significantly affected the fungal community composition in moss crusts of the study area.Total P significantly affected the AM fungal community composition in moss crusts around the main mine,while available phosphorus,polyphenol oxidase,sucrase,alkaline phosphatase and catalase significantly affected the AM fungal community composition in moss crusts around north dump.6.Seven bacterial strains with strong tolerance to heavy metals ions were screened from moss crusts soil.Pseudomonas kmineensis strain Cu1 was resistant to1500 mg/L Cu²⁺,Agrobacterium rubi strain CB1,Ornithinimicrobium sp.strain CB2and Kocuria dechangensis strain CH1 were resistant to 700 mg/L Cr⁶⁺,Peribacillus frigoritolerans strain MB2,Stenotrophomonas rhizophila strain MH2 and Staphylococcus epidermidis strain MH3 were resistant to 5000 mg/L Mn²⁺.In conclusion,open-pit coal mining has a great influence on the coverage and distribution of mosses on the crusts,and the influence on the community composition of fungi（including AM fungi）is greater than that of bacteria,leading to significant changes in some nutrient contents and enzyme activities in moss crusts soil.With the increase of distance gradient,the influence decreases.Soil nutrient content and enzyme activity in mosses crusts soil were significantly correlated with microbial community composition.