Study On Diversity Of Grassland Vegetation And Microorganism Of Chahar Volcanic Group In Inner Mongolia

The Chahar volcanic group(including Huanghuagou volcanic group and Wulanhada volcanic group)is the only volcanic group that has erupted in the Holocene at the southern margin of the Mongolian Plateau.Because of its diverse volcanic types,clear geomorphological marks,well-preserved cones,and basically complete craters,it is known as the "museum" of natural volcanoes for studying the deep structure of the Quaternary crust.It is also an ideal model to explore the succession of biotic communities,biodiversity and their interaction with environment in volcanic areas.In this study,the Chahar volcanic group in Inner Mongolia was selected as the research area.Based on the advantage of interdisciplinary,the data of above-ground plant communities and the physicochemical information of underground soil were extensively collected.Subsequently,amplicon sequencing technology,using multivariate analysis to combine it with microbial community data.This study characterized the community composition and structural characteristics of vegetation and microbes in the area,clarified the response characteristics of soil microbes to multi-factor environments under volcanic disturbances.The main results and conclusions of this study are as follows:1)The species of Polygonum,Taraxaeum and Potentilla were the dominant plants in the Maar-type volcanic region,while some species of Gramineae and Leguminosae as dominant plants in montane meadow steppe.The richness and diversity of microbial communities in montane meadow steppe were significantly higher than that of Maar volcanoes(P < 0.05),and there were more nodes(114 vs.74),edges(349 vs.291)and modules(10 vs.8).Under the turbulent environment of the Maar-type volcanoes,the metabolic activities related to the reabsorption of sodium and calcium of microorganisms were improved,and the lichen saprophytes were enriched.Principal coordinate analysis(PCo A)showed that the total variation of bacterial community was significantly greater than the total variation of fungal community(77.19% vs.46.07%).The core microbiome of these bacteria and fungi cooperated with each other,and the combined contribution of the interaction of soil factors and vegetation factors was greater than the individual contribution of a single type of factor.2)The diversity and species abundance of plant community in Stromolian-type were lower than those in typical steppe area.And some specific species such as Caragana microphylla,Astragalus melilotoides and Scutellaria baicalensis were adapted to the volcanic environment.Compared with the Strombolian-type volcanic area,the typical steppe area had a higher effective enrichment ratio of the core microorganisms of bacteria and fungi(66% vs.34% and 59% vs.41%,respectively),and had a higher degree of modularity network(M: 0.626 vs.0.296),simpler network connection(avg K: 4.374 vs.8.795;avg CC: 0.337 vs.0.467)and stronger inter-species competition(P/N: 1.89 vs.3.06).Compared with the typical steppe area,the bacterial metabolic activity in the Strombolian-type volcanic area was significantly improved,and many arbuscular mycorrhizal fungi were significantly enriched.In the entire community structure and function,a total of 7 keystone taxa(including 6 bacteria and 1 fungus)were detected,that is,soil bacteria may play a more important role than fungi.Soil phosphorus(S?AP)and soil carbon-nitrogen ratio(S?C/N)were the key potential driving factors of microbial community diversity in Strombolian-type volcanic area and typical steppe area,respectively.Structural equation modeling(SEM)showed that the same keystone taxa can perform different functions in different ecological environments,and the causal relationships between them and different environmental variables were not the same.3)Late Pleistocene volcanoes were dominated by some species of Poaceae,Allium and Salsola,etc.But the dominated plants in Holocene volcanoes are belong to Allium,Artemisia and Leonurus,etc.The plant species abundance,vegetation richness and diversity of Holocene volcanoes were significantly lower than those of Late Pleistocene volcanoes(P < 0.05).Although the microbial community ? diversity(richness,diversity,and evenness)of the Late Pleistocene volcanic soil was significantly higher than that of the Holocene volcanic soil(P < 0.05);the Holocene volcanic soil held more complex microbial community network structure than the Late Pleistocene volcanic soil.Quaternary volcanic soil was rich in some microbial groups with special functions(i.e.,biomarkers and keystone taxa),such as Nitrososphaera,Microvirga,and Cladosporium,which were closely related to the metabolism of soil carbon,nitrogen,and phosphorus.In addition,the soil bacterial community was more sensitive to the Quaternary volcanic soil environment than the fungal community,and that includes more biomarkers(17 vs.16).Quaternary volcanic soils first influenced soil carbon,nitrogen,and phosphorus,and then guided vegetation diversity,thereby regulated the microbial multifunctionality.4)There was no obvious difference in vegetation diversity between cinder cones and spatter cones(P > 0.05).The endemic plant species in the cinder cones were Allium tenuissimum,Thalictrum squarrosum,and Amaranthus retroflexus.The endemic plant species in the spatter cones were Taraxaeum mongolium,Erodium stephanianum,Lepidium apetalum and Stellaria media.The plant height,crown breadth,wet weight per plant and above-ground biomass of the main plants in cinder cones were significantly higher than those of spatter cones(P < 0.05).The microbial abundance in the cinder cones was significantly higher than that in the spatter cones(P < 0.05),and there were enriched in many arbuscular mycorrhizal fungi,which have been detected as keystone taxa and play a key role in the network relationship of soil fungal communities.Spatter cones significantly improved the microbial carbohydrate and amino acid metabolism,and held a more complicated interspecies relationship than cinder cones.12 fungal core microbiomes were the keystone taxa(including 10 in cinder cones,2 in spatter cones)in the microbial co-occurrence network.Above-ground biomass and soil moisture had significant influences on the soil microbial communities in the two types of volcanic cone ecosystems,and ?diversity was the largest positive contributor to microbial multifunctionality(? =0.786,P < 0.001).In conclusion,there were significant differences in the diversity of plant community and soil microial community and their interaction between the volcanoes of different types and chronological sequences of the Chahar volcanic group and the surrounding grassland area.Volcanic activity changed the diversity of plant community driven by soil substrate and the versatility of microbial regulation.This study laid a foundation for further exploring the evolution law of Quaternary volcanic community and the mechanism of volcanic activity on grassland ecosystem.