Effect Of Water Status On Nitrogen Transformation And Microbial Properties Of Northeastern Mollisols

In recent years,atmospheric problems caused by greenhouse gas emission are obvious.N₂O is the second greenhouse gas which needed to be controlled after CO₂and CH₄.N₂O which emitted from soil is the main source of N₂O production.There are many factors that affect the emission of N₂O in the soil.Among them,water status may affect the activity of nitrifying and denitrifying microorganisms in the soil and affect the conversion of nitrogen in the soil and the production and emission of N₂O.In this paper,the black soil of northeast China is taken as the research object.The culture method is combined with molecular biological techniques including DNA extraction,real-time PCR,high-throughput sequencing,and other molecular biological techniques,including nessler's reagents spectrophotometer,ultraviolet spectrophotometry and gas chromatography as well.The effects of different water status and different gas filling conditions on the functional gene copy number,population and nitrogen transformation.Microorganisms in the soil provides a scientific basis for the practice of N₂O production and discharge in northeast black soil and the study of N₂O production and discharge pathways.The paper concludes as follows:(1)Under the condition of 40%WHC moisture status,the nitrification mainly occurs in the soil.The dominant classes of microorganisms are Actinobacteria and Thermoleophilia,and the dominant genera are Paenibacillus and Sporosarcina.At 80%WHC moisture status,the nitrification and the nitrification is carried out at the same time,but the denitrification intensity is greater than the nitrification.The nir S gene and the nos Z gene are the main functional genes to promote the denitrification.The nos Z gene is the key gene to promote the conversion of N₂O to N₂.The dominant classes of microorganisms are Betaproteobacteria and Alphaproteobacteria,and the dominant genera are Methylobacterium and Coprococcus.(2)The nitrification mainly occurs in low-moisture soils,the copy number of the ammonia oxidation function gene increases,the nitrification produces less N₂O,and the high-moisture status soil nitrification and denitrification function gene copy numbers are many,and complete denitrification.The converts N₂O to N₂,and the N₂O emission status is relatively small;under 10%acetylene conditions,acetylene inhibits the nitrification and the activity of the nos Z gene.With the increase of the moisture status,the nir S gene copy number increases,which further promotes denitrification.Accordingly,the emission of N₂O increased,but the conversion process of N₂O to N₂was inhibited,resulting in a large amount of accumulation of N₂O;under aerobic conditions,the number of copies of the ammonia oxidation function gene is more.With the increase of water status,some soil samples appear the anaerobic zone,the denitrification is slightly enhanced,and the emission of N₂O is converted to N₂,and a small amount of N₂O accumulation occurs.Under anaerobic conditions,the nitrification is suppressed,which promotes the denitrification and is accompanied by a large amount of N₂O.As the number of gene copies increases,N₂O is further reduced to N₂.