Effects Of Increased Nitrogen Deposition And Changing Rainfall Patterns On Soil Microbial Communities In Stipa Breviflora Desert Steppe

Increased atmospheric nitrogen deposition and precipitation change are important phenomenon in global climate change,and their impact on grassland ecosystems has become a hot issue in the field of ecology,The desert grassland is restricted by both water and nitrogen,and it has the leading indicator of global change.Studying the effects of nitrogen deposition and precipitation change on soil microbial communities in desert grassland ecosystems can provide a theoretical basis for comprehensive analysis and assessment of the impact of global changes on grassland ecosystems,the rational use of grasslands,biodiversity conservation,and the restoration of degraded grasslands.The water and nitrogen manipulation experiment in Stipa breviflora desert steppe is based on the field control experiment platform using split-plot design,with water as the whole-plot factor and nitrogen as the sub-plot factor,including twelve treatments.Water treatment includes CK(natural rainfall),W(30%rainfall addition),R(30%rainfall reduction),and nitrogen treatment includes 0(N0),30(N30),50(N50),100(N100)kg N·hm^-2·a^-1.We used high-throughput sequencing technology to study the effects of nitrogen deposition and precipitation change on soil bacterial and fungal community structure and its diversity in the Stipa breviflora desert steppe in Inner Mongolia.Our results show that:(1)Community structure and diversity of soil bacterial differently responded to nitrogen addition and precipitation change are in the Stipa breviflora desert steppe.The dominant bacteria in the soil bacterial community are Actinobacteria(34.61%?49.13%),Proteobacteria(13.09%?22.07%),Chloroflexi(11.99%?20.22%),Acidobacteria(7.88%?20.15%),Gemmatimonadetes(1.82%?4.28%).Among them,the relative abundances of Actinomycetes,Actinobacteria,Chloroflexi and Acidobacteria have significant changes,which can be used as indicator species for changes in soil bacterial community structure in Stipa breviflora desert steppe.Nitrogen addition and water change altered the structure of soil bacterial communities,water change affected the diversity of soil bacteria significantly.Compared with other water treatments at the same nitrogen level,water enhancement treatment increases the diversity of the bacterial community significantly.The effects of different water and nitrogen treatments on the diversity of soil bacterial community metabolic function genes and the relative abundance of genes are not obvious.(2)Community structure and diversity of soil fungus differently responded to nitrogen addition and precipitation change are in the Stipa breviflora desert steppe.The dominant phylum in the soil fungal community is Ascomycota(36%?76%),Mortierellomycota(3.2%?43.6%),Basidiomycota(5.85%?31.22%),Glomeromycota(1.32%?7.14%),Chytridiomycota(0.24%?6.12%),Olpidiomycota(0.13%?1.34%).Among them,Curvularia of Ascomycota and Claroideoglomeraceae of Coccus have the most obvious changes in relative abundance,which can be used as indicator species for changes in soil fungal community structure in Stipa breviflora desert steppe.Nitrogen addition and water change altered the soil fungal community structure,and water change had significant impact on the richness of soil fungal communities.The effects of different water and nitrogen treatments on the diversity of fungal community metabolic functional genes are similar,but the changes in the relative abundance of functional genes are different.(3)Different nitrogen addition and water change have different effects on plant characteristics,soil physical and chemical properties and enzyme activities.Water change affected the aboveground biomass and diversity index of plants significantly.Nitrogen addition promoted the accumulation of aboveground biomass of plants and had significant impact on plant diversity index.Water addition amplified the positive effects of nitrogen addition on plant diversity and above-ground biomass.Under the same water condition,nitrogen addition decreased soil p H and increased the available nitrogen content.Different nitrogen addition and water change had no significant effects on soil organic carbon and total nitrogen content.Water change had significant impact on soil water content.Water change and nitrogen addition had significant impact on soil p H.Water,nitrogen,water and nitrogen all had significant impact on soil available nitrogen content.Water change significantly affected the activities of soil catalase and sucrase.Nitrogen treatment significantly affects the activities of soil catalase,sucrase and urease.The interaction of water and nitrogen has a significant impact on soil catalase activity.Soil catalase,sucrase,urease activities and soil nitrate-nitrogen content showed significant negative correlation.(4)Under different water change and nitrogen addition,the main factors affected the change of soil bacterial communities are plant biomass,soil water content,p H value,NO₃^--N content,sucrase and urease activity.The main factors that change soil fungal communities are soil p H,NH₄⁺-N content and catalase activity.Different organisms and their diversity have different responses to nitrogen addition and water changes.To reveal the impact of nitrogen addition and water change on grassland ecosystems,more in-depth,long-term,and comprehensive networking research on multiple organisms will be needed.