The Soil Microbial Diversity And Spatial Variation Of Degraded Alpine Meadow In Sanjiangyuan Region

The alpine meadow ecosystem is the main ecosystem of the Qinghai-Tibet Plateau.In recent decades,climate change and overgrazing has caused serious degradation of the alpine meadow,which has been affected on the production and life of the local people,and also affected the soil microbial ecosystem.The soil microorganisms play key roles in the stability and succession of grassland ecosystems,their response to grassland degradation has not been investigated at spatial scale.Therefore,this paper from the vegetation and soil characteristics,soil microbial diversity and construct the mechanism of system analysis of degraded alpine meadow,which aims to understand the formation of soil microbial community structure in the process of grassland degradation mechanism,and also provides a theoretical basis for grassland degradation control.In this study,we contrasted and analyzed the vegetation,soil and soil mocrobial communities of undegraded alpine meadow and degraded alpine meadow,we mainly studied the changes in soil microbial community diversity and the mechanism of microbial community construction.The main research results are as follows:(1)Meadow degradation has significantly changed the vegetation community and soil physical and chemical characteristics.The composition of vegetation community in the undegraded alpine meadow was more complex and diverse,and the species diversity index and vegetation productivity were higher than in the degraded alpine meadow.In addition,the soil organic matter content,water content and electrical conductivity of the undegraded meadow were higher than of the degraded alpine meadow,while the soil p H was lower than that of the degraded meadow.(2)Soil microbial?-diversity and composition differed significantly between the two sample plots.Specifically,compared to undegraded alpine meadow,the?-diversity of soil prokaryotes was significantly lower in the degraded alpine meadow,but the fungal is opposite.At the phylum level,compare to the undegraded meadow,the degradation significantly increased relative abundance of Actinobacteria,Bacteroidetes,by 3.21%,22.14%,and decreased relative abundance of Verrucomicrobia by approximately 31.85%.Soil fungi,the degradation significantly increased relative abundance of Ascomycota,while the relative abundance of Basidiomycota decreases.Environmental factors have a certain impact on the soil microbial community.Soil p H,OM,TN and vegetation coverage have significant effects on prokaryotes,while soil p H,OM,NO3~--N and the number of vegetation species affect fungi stronger.Prediction analysis of microbial function results found the relative abundance of nitrifying bacteria in the soil after the degradation of meadows by prokaryotes will increase significantly,and the relative abundance of pathogenic fungi in the soil after the degradation of meadows in fungi.This result indicates that meadow degradation will increase the leaching loss of inorganic nitrogen in the soil and increase the risk of vegetation disease.(3)The spatial scale distribution pattern of soil microbes explains the relationship between distance decay relationship and species area relationship of soil microbial communities in undegraded meadows and degraded meadows,and with the degradation of meadow,the spatial turnover rate of prokaryotic(Degraded meadow?=0.0035,P<0.001\z=0.0294,P<0.05,Undegraded meadow?=0.0030,P<0.001\z=0.0254,P<0.05)and fungal(Degraded meadow?=0.0142,P<0.001\z=0.0690,P<0.010,Undegraded meadow?=0.0077,P<0.001\z=0.0620,P<0.010)species increase.s,this is mainly due to soil heterogeneity and dispersal limitation of the microbial.The impact of deterministic and stochastic processes on soil microbial?diversity and the main environmental driving factors representing the deterministic process are different,and there are significant differences between microbial species.Specifically,the prokaryotic communities of undegraded meadows and degraded meadows are mainly affected by stochastic processes(stochastic ratio>80%v.s.deterministic ratio<20%),the fungal communities of undegraded meadows are also affected by stochastic processes(58%v.s.42%),and the fungal communities of degraded meadows are mainly affected by deterministic process(34%v.s.66%).(4)The method of variable decomposition further proves that geographic distance and environmental factors have an impact on community turnover,but geographic distance is the main influencing factor,and environmental factors only affect fungal communities in degraded meadows.Therefore,by accurately measuring each assembly process in geographical distance,it is found that the proportion of the diffusion restriction of the fungal community is increasing with the increase of geographical distance,and the proportion of homogeneous selection is decreasing.There is no obvious difference between the two assembly processes in the undegraded meadow.Prokaryotic communities in undegraded meadows and degraded meadows have no obvious changes in dispersal limitation and homogeneous selection with the increase of geographic distance.These results indicate that with the increase of geographical distance,the influence of dispersal limitation on prokaryotes and fungal communities is intensified,and at the same time,the assembly of fungal communities in degraded meadows plays an increasingly important role.Our results suggest that meadow degradation had a significant impact on soil microorganisms.Meadow degradation resulted in a decrease in prokaryotic?-diversity,while an increase in fungi,and also resulted in a significant change in microbial?diversity.In addition,our system analyzed the?diversity of soil microbial communities in degraded meadow,emphasized the importance of different?diversity,geographic distances,and environmental variables to the construction process of soil microbial communities,and analyzed the main reasons that led to the increase in the spatial turnover rate of microbial communities.We found that the increase in the spatial turnover rate of prokaryotes in the degraded meadow system is mainly due to dispersal limitation,while in the fungal community it is the simultaneous effect of niche selection and dispersal limitation.Therefore,our research reveals the mechanism of soil microbial community construction in degraded meadows on a spatial scale,and provides new information for us to better predict grassland degradation and evaluate grassland health.