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Effect Of Different Saline-alkali Stress On Soil Nitrogen Transformation And Ammonia-oxidizing Microorganisms

Posted on:2019-06-14Degree:MasterType:Thesis
Country:ChinaCandidate:H M ZhangFull Text:PDF
GTID:2370330596955565Subject:Soil science
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[Object]Soil salinity is an important problem faced by agricultural soils in arid and semi-arid areas.Salt and alkali can lead to microbial communities changed significantly.Ammonia-oxidizing bacteria?AOB?and ammonia-oxidizing archaea?AOA?play an important role in the nitrification process,nitrification is the central link in the process of nitrogen transformation,microbial changes will inevitably affect soil nitrogen transformation.We studied the effects of different salinity types and salinity on soil nitrogen transformation and soil microbial community,to discusse the changes of ammoxidation microbial communities under different saline-alkali types,and revealed the relationship between ammonia-oxidizing microorganisms and saline-alkali stress.In order to provides a scientific basis in traditional application of nitrogen fertilizer.[Method]This study is divided into two parts:a pot experiment and a culture experiment.The pot experiment was carried out in 2016.The two-factor experiment design was adopted.According to the classification of saline-alkali types and classification standards stipulated by the second national soil census,three saline-alkali types,chloride,sulfate and alkali stress were set by adding NaCl,Na2SO4 and NaHCO3.The salinity and alkalinity were set at three levels,non saline?alkali?stress,mild saline?alkali?stress and moderate saline?alkali?stress.The pot experiment was conducted to study the effects of saline-alkali stress on the diversity of soil bacterial and fungal community.The culture experiment was conducted in 2017.The two-factor experiment design was adopted.The type of salt-alkali stress was the same as the pot experiment.There were three levels of salinity:non-saline-alkali stress,moderate saline?alkali?stress and severe saline?alkali?stress.The culture experiment was conducted to investigate the effects of different saline-alkali stress on nitrogen transformation and ammonia-oxidizing microorganisms.[Result]?1?Moderate NaCl stress increased soil inorganic nitrogen content significantly and promoted soil mineralization,while moderate Na2SO4 and NaHCO3 stress had no significant effect on inorganic nitrogen content.Moderate NaCl stress reduced nitrogen nitrification significantly,and the inhibition was significantly higher than moderate Na2SO4 stress and moderate NaHCO3 alkali stress.?2?Na2SO4 and NaHCO3 stress reduced the Chao1 and Ace richness indices of soil bacteria communities significantly.Bacteroidetes,Planctomycetes and Thaumarchaeota increased,while Actinobacteria and Nitrospira decreased.The difference species of bacterial community in moderate salinized NaCl soil were Proteobacteria.Acidobacteriales and Acinetobacter of Proteobacteria were slightly salinized by Na2SO4 soil,and Actinomycetes were unclassified in moderately salinized soil.And in mild alkalized soil by NaHCO3 were Pseudomonas aeruginosa?Acinetobacter?,in moderate alkalized soil were Acidobacteria,Sphingomonas of Proteobacteria.?3?Soil fungal communities under NaCl and Na2SO4 stress were highly similar?97%?to those under NaHCO3 stress.Mild NaCl and Na2SO4 stress increased soil fungal community richness significantly,mild NaHCO3stress reduced soil fungal community Chao1 and Ace richness index significantly,moderate NaHCO3 stress increased it significantly.Saline-alkali stress increased the relative abundance of ascomycota significantly,and the effect of saline stress was higher than that of alkali stress.?4?NaCl stress increased AOA abundance significantly,while Na2SO4 and NaHCO3 stress decreased AOA abundance significantly.Severe salinization of NaCl,Na2SO4 and NaHCO3 reduced AOB abundance significantly,but the effect of saline stress on AOB was higher than that of alkali stress under severe saline-alkali stress treatment.?5?Severe NaCl and Na2SO4stress reduced the AOB diversity index significantly.Moderate NaHCO3 alkali treatment increased Chao1 and Ace index significantly.RDA analysis showed that the main environmental factors are pH,electrical conductivity and organic matter of AOA community,while the main environmental factors affecting AOB community were ammonium nitrogen,nitrate nitrogen,electrical conductivity and pH.[Conclusion]Saline-alkali stress?NaCl,Na2SO4,NaHCO3?increased the content of inorganic nitrogen in soil significantly,promote soil nitrogen mineralization.The change appears because of some microbial that can degrad organics such as Proteobacteria and unclassified Actinomycetes changes.Saline-alkali stress can inhibit nitrification and correlation with the abundance and the structure of AOB community changed.
Keywords/Search Tags:Saline-alkali stress, Bacteria, Fungi, Ammonia-oxidizing bacteria, Ammonia oxidation archaea
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