Mechanisms Of Influence Of Long-term Nitrogen Deposition On Soil Microbiomes In Stipa Baicalensis Steppe

Carbon and nitrogen cycles of grassland ecosystem,as the basic ecological processes,regulate and maintain ecosystem productivity and stability.Soil microbe is the main driving force of soil carbon and nitrogen cycling process.Enhanced atmospheric nitrogen deposition is one of the most important phenomena of global change,but its effect on the carbon and nitrogen cycles and their feedback in grassland ecosystem remains uncertain.Studying the coupling relationship between soil carbon/nitrogen transformation and microbial community succession is essential to reveal these uncertainties,and would provide scientific basis for improving the soil carbon accumulation and reducing the nitrogen losses.A field control experiment to simulate nitrogen deposition would be implemented in Inner Mongolia Stipa baicalensis steppe.Using molecular biology technologies,we would reveal the mechanisms of influence of nitrogen deposition on soil microbial community structure and diversity.Meanwhile,the changes of soil microbial community and the main related functional groups responding to carbon and nitrogen transformation and their succession regulation would be explored in this research.The results showed that:(1)N addition led to significant increases in the concentrations of SOC.Structural equation modeling further revealed that soil pH and bacterial community structure(Proteobacteria and Planctomycetes)have an impact with SOC under N deposition.(2)N addition led to significant alter cbbL gene community composition,decreases in cbbL gene abundance and genetic diversity and.N addition indirectly reduced cbbL gene abundance,possibly by increasing the soil N/phosphorus(P)ratio and decreasing the soil pH.N addition primarily reduced cbbL genetic diversity by increasing the soil NO3-N content and decreasing the soil pH.(3)N addition primarily reduced the abundance and diversity of nifH-containing microbes by altering soil NO3-N content and soil pH.This study would reveal the response regulation of soil physical and chemical factors and the mechanism of microbial community under enhanced nitrogen deposition,and then provide a theoretical basis for the analysis and evaluation of nitrogen deposition effects on grassland ecosystem,and provide theory basis for the reasonable utilization of grassland,the biodiversity conservation,and the restoration of degraded grassland.