Effects Of Simulated Nitrogen Deposition And Precipitation On Plant Community, Soil And Soil Fungal Community In A Stipa Baicalensis Grassland

Nitrogen deposition and precipitation pattern change has a profound impact onterrestrial ecosystems. There are predictions that nitrogen deposition and precipitationshow a increasing trend of northern China in the future. To explore the changes ofgrassland vegetation, soil and soil fungi community in grassland under increasednitrogen deposition and precipitation, We designed the experiment with the nitrogenaddition and increased precipitation in a Stipa baicalensis grassland of eastern InnerMongolia, we set up different gradients of nitrogen and precipitation and observedchanges in plant communities, soil and soil fungi community. We combineddenaturing gradient gel electrophoresis(DGGE) and phospholipids fatty acid (PLFA)methods with soil microbial ecology, We attempted to answer the three scientificquestions:(1) How the features of plant community change under the condition ofnitrogen addition and increased precipitation?(2) What were the main changes of soilphysical and chemical properties under the condition of nitrogen addition andincreased precipitation?(3) What were the rules of fungal community structure anddiversity change and the relationships between plant community and soil factorsunder the condition of nitrogen addition and increased precipitation?The main conclusions and results were as follows:(1) Increased nitrogen increased plant community coverage significantly, butreduced the plants richness and diversity. Increased precipitation had no significanteffect on plant community, the interaction of nitrogen addition and increasedprecipitation had no significant effect on plant community.(2) Nitrogen addition significantly increased the inorganic nitrogen in the soil.Increased precipitation had a significantly effect on total phospholipids fatty acid andC/N. It had a significant impact on pH, increased first then decreased.The interactionof nitrogen addition and increased precipitation had a significant effect on inorganicnitrogen.(3) Inorganic nitrogen had a significant effect on fungal community. Fungalcommunity had a significant positive correlation with the C/N, This suggested thatincreasing nitrogen improved the soil environment. However, that the effect on fungalcommunity diversity was not fixed, reflected that the effect of increased nitrogen onfungal community were complex and diverse.(4) Increased nitrogen decreased total microbial phospholipid fatty acid content, but significantly increased the the ratio of fungi:bacteria. This suggested thatincreased nitrogen may change the composition of microbial community.Precipitation significantly changed the content of bacteria PLFA, but did notsignificantly affect fungal communities; Fungal communities had a significantlynegative correlation with moisture in the soil; This suggested that increasedprecipitation had a negative effect on the growth of fungal communities in the Stipabaicalensis grassland; Fungal communities may be more adaptive to grow in dryenvironment.(5) The interaction of nitrogen addition and increased precipitation had nosignificant effect on soil fungal community structure and diversity. The evennessbetween plant community and soil fungal community had significantly positivecorrelation, other diversity index had no significantly effect on fungi.