Effects And Differences Of Different Dominant Shrubs On Soil Microorganisms And Nematode Communities In Alpine Meadow Of Southeast Qinghai-Tibet Plateau

As main vegetation type of Qinghai-Tibet Plateau,alpine meadow had been frequently affected by climate warming in recent years,and then shrubs in alpine meadow had obvious expansion trends,which had significant impacts on diversity and community composition of soil biome.Soil microbes and nematodes are important parts of soil biome,they are essential in maintaining stability of soil ecosystems.Previous studies have found expansion of dominant shrubs can change structure and diversity of soil biome,but most of these studies have focused on effects of single dominant shrub on soil bacterial,soil fungal and soil nematode community,while fewer studies have examined the effects of different dominant shrubs on soil bacterial,soil fungal and soil nematode communities,so as to difficult to accurately reveal the difference and mechanism in impacts of different dominant shrubs on soil biological community.We chose bacteria,fungi,and nematode in soil of dominant shrubs,such as Dasiphora Fruticosa,Salix oritrepha,and Rhododendron capitatum in alpine meadow of southeast Qinghai-Tibet Plateau as our experimental objects.We used One-way ANOVA to explore different effects of dominant shrubs on edaphic properties,and on diversity,community composition of soil bacterial,fungal and nematode community.Rrelationships between soil bacteria,fungal,nematode community and edaphic properties were analyzed through Spearman correlation analysis.Different effects of dominant shrubs on community composition of soil bacteria,fungi and nematode and the key edaphic properties of dominant shrubs affecting soil bacterial,fungal and nematode communities were analyzed by nonmetric multidimensional scaling and redundancy analysis.Our study found that:(1)Dasiphora fruticose significantly promoted soil nitrate content by 58.25 %compared with Salix oritreph(P < 0.01).Rhododendron capitatum significantly promoted total nitrogen content by 20.49% compared with Salix oritreph(P < 0.05).Salix oritreph significantly promoted soil ammonium content by 31.17 % compared with Dasiphora fruticose(P < 0.1).Other edaphic properties had no significant difference in different dominant shrub soil.(2)The richness and Shannon diversity of soil bacterial community had no significant difference in different shrub soil,Rhododendron capitatum significantly promoted bacterial biomass by 202.29 % compared with Salix oritreph(P < 0.001).Results of Spearman correlation showed soil bacterial biomass was significantly positive correlated with soil total nitrogen content.Dominant shrubs had significant impacts on soil bacterial community composition.Rhododendron capitatum significantly promoted the relative abundance of Proteobacteria compared with Dasiphora fruticosa.Dasiphora fruticosa significantly promoted the relative abundance of Nitrospirae compared with Rhododendron capitatum.Results of RDA showed the most critical edaphic property of dominant shrubs affecting soil bacterial community composition was soil ammonium content.Results of Spearman correlation showed the relative abundance of Proteobacteria was significantly negative correlated with soil nitrate content;the relative abundance of Nitrospirae was significantly negative correlated with soil ammonium content,significantly positive correlated with soil nitrate content.(3)Dasiphora fruticosa significantly promoted soil fungal community richness by 22.89 % compared with Rhododendron capitatum(P < 0.05),Shannon diversity and biomass had not significant difference.Results of Spearman correlation showed soil fungal community richness was significantly negative correlated with total nitrogen content and significantly positive correlated with soil nitrate nitrogen content.Different dominant shrubs had significant impacts on soil fungal community composition.Dasiphora fruticosa significantly promoted the relative abundance of Mortierellomycota and Glomeromycota compared with Salix oritreph.Results of RDA showed the most critical edaphic property of dominant shrubs affecting soil fungal community composition was soil ammonium content.Results of Spearman correlation showed the relative abundance of Mortierellomycota was significantly negative correlated with soil ammonium content,significantly positive correlated with soil nitrate content;the relative abundance of Glomeromycota was significantly positive correlated with soil nitrate content.(4)The richness and Shannon diversity of soil nematode community had no significant difference in different dominant shrub soil,but abundance and biomass had marginally significant difference(P < 0.1).Salix oritreph marginally significant promoted plant feeder nematode richness(P < 0.1),significantly promoted Shannon diversity(P < 0.01),marginally significant promoted predator-omnivorous feeder nematode abundance and biomass(P < 0.1)compared with Rhododendron capitatum.Results of Spearman correlation showed soil nematode abundance was negatively correlated with soil water content and total phosphorus content;soil nematode biomass was negatively correlated with soil total phosphorus content.Dominant shrubs had significant impacts on nematode community composition,Salix oritreph significantly promoted abundance of Prodorylaimium compared with Rhododendron capitatum.Results of RDA showed most critical edaphic properties of dominant shrubs affecting nematode community composition were soil total nitrogen content and water content.Results of Spearman correlation showed abundance of Prodorylaimium was significantly negative correlated with soil tatal nitrogen content.Basal index(BI)of soil nematode community in soil of Rhododendron capitatum was marginally higher than Salix oritreph(P < 0.1).In conclusion,dominant shrubs had significant effects on diversity and community composition of soil bacteria,fungi and nematode,and these impacts were closely related to edaphic properties.Dominant shrubs had greater impacts on biomass of soil bacteria,bacterial biomass was higher in soil of Rhododendron capitatum,these impacts may be caused by positive relationship between soil total nitrogen content and bacterial biomass.Dominant shrubs had greater impacts on richness of soil fungal community,and fungal community richness was higher in soil of Dasiphora fruticose,these impacts may be caused by positive relationship between soil total nitrate content and fungal richness.Dominant shrubs had greater impacts on abundance and biomass of soil nematode,these impacts may be related to soil water content and phosphorus content.Our results are of great importance for mechanism exploration of effects of different dominant shrubs on soil biome diversity and community composition,this also can deepen our understanding of the mechanisms by which shrub expansion affect belowground biome diversity,and also provide theoretical support for soil biodiversity conservation and maintenance of soil ecological functions in alpine meadow of Qinghai-Tibet Plateau.