Study On Diversity Of Vegetation And Soil Microorganisms Of Steppes In Central Mongolia

Mongolia has complex landforms and rich and diverse grassland types.The zonal vegetation distribution belt displays a diverse and differential changes of plant and soil microbial(AM fungi)communities created by hydrothermal gradient changes.It has unique geographical,climatic,and relatively primitive landscape characteristics,making it an ideal model for studying the composition and diversity of grassland ecosystem vegetation and soil microbial communities.In this study,four types of steppe vegetation(Desert Steppe,Typical Steppe,Meadow Steppe and Upland Steppe)and desert vegetation(Gobi Desert)and its transition areas(transition zone between Gobi Desert and Desert Steppe,transition zone between Typical Steppe and Meadow Steppe)in Central Mongolia were selected,and the structure,differential characteristics and ecological environment influencing factors of biological communities in different vegetation types were compared through interdisciplinary analysis methods.This study explored the plant-soil microbial-AM fungal interaction network and compared and evaluated the stability of different vegetation types of ecosystems.The main results and conclusions of this study are as follows:1)In the study area,a total of 108 major plant species belonging to 79 genera of27 families were investigated.Among them,the dominant plants in the Gobi Desert,Desert Steppe,and its transitional zone were mainly Caragana(Drought tolerant),Stipa(small forage grass),and Salsola(Chenopodiacea).In the Typical Steppe,the dominant plants were mainly xerophyte,including Stipa,Leymus,Festuca,and Artemisia.The dominant plants in Meadow Steppe were mainly mesophyte(Androsace,Draba and Achillea)and xerophyte(Festuca,Carex and Artemisia).The plant compositions in the transition zone and the Upland Steppe were similar to that in the Meadow Steppe and Typical Steppe.The plant community diversity was highest in the Upland Steppe,followed by Meadow Steppe,Typical Steppe and its transition zone,the Gobi Desert,Desert Steppe and its transition zone were lower.The plant diversity was influenced by temperature and precipitation,and significantly correlated with soil C/N ratio,p H,and phosphatase activity(p<0.005).The AM mycorrhizal structure type of common plants in Mongolian Plateau grassland was mainly Arum-type,not directly related to plant life cycle and root type,and colonization rates in Paris-type plants were relatively low.2)The correlation between aboveground vegetation and soil fungi was closer than that of soil bacteria.There were differences in the composition and relative abundance of dominant microbial flora across different vegetation types.In the transition from the Gobi Desert to the Desert Steppe,the dominant soil microbial flora changed from Acremonium(high salinity and alkalinity-adapted)and Monosporascus(halophyte-associated)to RB41 and Darksidea(possess organic matter decomposition and transformation functions).Bradyrhizobium,which has the functions of nitrogen fixation and hydrolysis of organic phosphorus,was a potential indicator for Meadow Steppe.Soil bacteria with characteristics such as heat resistance,cold resistance and acid resistance had significant differences indirectly caused by local climate characteristics differences in the different spatial distribution of Upland Steppe.The soil microbial community was mainly driven by soil moisture content,C/N ratio,longitude,total sulfur and nitrate nitrogen.The ecological and environmental factors affecting soil microbial communities increased with increasing vegetation coverage,the C/H ratio and soil enzyme activities(UE,CAT,SC,ACP,AKP,and NP)had impact on soil microbial communities in the Typical Steppe,Meadow Steppe and Upland Steppe.3)In the study area,the common genera of soil AM fungi were Acaulospora,Glomus,and Septoglomus,and the common species were A.sp1,C.etunicatum,G.reticulatum,G.versiforme,G.sp2,Sept.constrictum and Sept.turnauae.The distribution of AM fungal communities exhibited low heterogeneity,all genera were worldwide distribution and 17 species were worldwide distribution accounting for 80%of the clearly identified species.The Altitude,soil p H,moisture content,C/N ratio,NN,TP,and AP were the main influencing factors in different vegetation types.Among them,soil p H was the driving factor for AM fungal communities in Typical Steppe,and had an extremely significant correlation with Glomus-viscosum-VTX00063(R=0.4412,p<0.001).The ecosystem stability of Typical Steppe,Meadow Steppe and Upland Steppe were higher than that of Gobi Desert and Desert Steppe,and the transitional zone had an unstable ecosystem and lower network complexity as an intersection of two vegetation types.In summary,there were significant differences in the composition and diversity of vegetation and soil microbial(AM fungi)communities among different types of steppes in central Mongolia,which were comprehensively influenced by various ecological and environmental factors.This study had theoretical and practical significance for understanding the interaction and influence of vegetation and soil microorganisms,functional composition,stability and maintenance mechanisms of grassland communities in grassland ecosystems.