The Effects Of Simulated Nitrogen Deposition On The Soil Microbial Community Structure And Diversity Of The Coastal Wetlands In The Yellow River Delta

The soil microorganism has the function of regulating ecosystem function,as a medium of the internal and external environment of the ecosystem.Currently,with the increase of fertilizer application and fossil fuel combustion,the global nitrogen deposition is increasing year by year.The nitrogen content in the soil increases rapidly,which will have a significant influence on the diversity and structure of soil microbial community,which will affect the growth of vegetation and change the cycle of carbon and nitrogen.In the present study,high-throughput sequencing was used to study the effects of simulated nitrogen deposition on the soil microbial community structure and diversity of the coastal wetlands in the Yellow River delta.Three different concentrations and kinds of nitrogen deposition were designed in this study.Briefly,the three kinds of nitrogen deposition was KNO₃?NH₄Cl?NH₄NO₃ and the concentration gradient was 5 g m^-22 yr^-1,10 g m^-22 yr^-11 and 20 g m^-22 yr^-11 with the control group(0g m^-22 yr^-1)set.The nitrogen had been added at the end of each month.The nitrogen deposition experiment was lasted 5 years?from 2012 to 2017?.The soil samples were collected in May 2017.The main results showed that:?1?The soil ammonium and nitrate content were rapidly increased after the different concentration of nitrogen treatment.Additionally,the plant growth was significantly increased under the NH₄NO₃ deposition treatment.The soil salinity decreased significantly,however,there was no significant change on other physicochemical properties and enzyme activity under the KNO₃?NH₄Cl deposition treatments.Generally,the above results showed that the nitrogen deposition could promote the growth of vegetation,the soil urease activity,and decrease the soil salt content.?2?The diversity and OTUs number indicated that nitrogen deposition reduced soil bacterial diversity,especially with the KNO₃ treatment.The redundant analysis between soil physical and chemical properties and soil diversity showed that the total nitrogen content was possibly the main factor that could influence the bacterial diversity in the studied region?p<0.05?.In addition,the nitrate,p H and salt content could possibly promote the diversity of microbial community in the soil.?3?The species annotation of representative sequence of OTUs indicated that the relatively distribution of dominant bacterial at the level of phylum,class and genus accounted for approximately 64%,32-38%and 7.5%of the entire bacterial community,respectively.No significant differences were observed on the dominant population at the level of phylum and class,however,the dominant population at the genus level has changed significantly,which indicated that the nitrogen deposition could mainly change the composition of the bacteria community at the genus level in the soil.?4?The analysis results of NMDS and MRPP showed that there was no significant change in bacterial community structure under the addition of potassium nitrate,however,it would change significantly under the LNH,MNN and HNN.This presented that the ammonium chloride and ammonium nitrate could possibly significantly change the composition of soil bacterial community.?5?The analysis results of effects of soil physical and chemical indexes on soil bacteria dominance genus after three kinds of nitrogen treatments illustrated that the effect of soil physical and chemical indexes on soil bacteria dominant genus was not significant after KNO₃ and NH₄Cl treatments.Additionally,the content of available phosphorus and ammonium nitrogen in soil was possibly the main factor that could influence the relative abundance of soil bacteria dominant genus?p<0.05?.The relative richness of Zeaxanthinibacter genus decreased but the Thiobacillus genus increased with the content of ammonium nitrogen increased.The relative richness of Marinicella genus increased,whereas the Thiobacillus,Hoppeia and Thioalkalispira decreased as the rapid available phosphorus concentration increased.