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Study On The Coupling Process Of Methane Oxidation And Biological Nitrogen Fixation In Typical Paddy Soils In China

Posted on:2021-08-23Degree:MasterType:Thesis
Country:ChinaCandidate:J ZhangFull Text:PDF
GTID:2480306452976169Subject:Applied Meteorology
Abstract/Summary:PDF Full Text Request
The methane aerobic oxidation mediated by methane oxidation bacteria is an important process of methane reduction in paddy soil.nitrogen is one of elements necessary in the process of crop growth,and it is one of the main limiting factors for increase of grain yield of rice.Biological nitrogen fixation is one of the important sources of active nitrogen input in paddy soil.It has been found that some methane oxidationbacteria have nitrogen fixation nifH genes,which may be indicator of biological nitrogen fixation,but the underlying mechanism of coupling processes of methane aerobic oxidation and biological nitrogen fixation,as well as its influencing factors,is not clear.it is generally believed that soil microorganisms initiate nitrogen fixation under nitrogen-free or nitrogen extreme deficiency conditions.Therefore,by measuring methane oxidation rate and nitrogen mineralization rate,paddy soils were divided into strong and weak nitrogen mineralization potential to further evaluate the nitrogen fixation potentialof soils with different methane oxidation characteristics.The physicochemical properties of 24 typical paddy soils from different regions of China were collected and the quantitative characteristics of pmoA and nifH genes in the soil were determined.There was positive correlation between the methane oxidation rate and the net nitrogen mineralization rate.On this basis,the stable isotope13C and15N tracer technique were used to study the typical methane oxidation potential.Soil nitrogen fixation ability,as well as response to different concentrations of CH4substrate,revealed the coupling process between methane oxidation and nitrogen fixation,explored the nitrogen fixationpotential and environmental microbial driving mechanism of typical paddy soil methane oxidation process in china.The findings are as follows:(1)There was a significant positive correlation between methane monooxygenase genes(pmoA)and nitrogen-fixing genes(nifH)in 24 typical paddy soils,indicating that methane-oxidizing bacteria had functional genes associated with methane oxidation and nitrogen fixation.The results of high-throughput sequencing of pmoA genes showed that,fourteen samples of paddy soils were dominated by Ia methane-oxidizing bacteria,one soil sample from Sichuan Ziyang was dominated by Ib methane-oxidizing bacteria.Nine samples of paddy soils were dominated by II methane-oxidizing bacteria.(2)Undisturded paddy soils were incubated with high concentration of methane to measure methane oxidation rate.The results showed that the methane oxidation rate ranges from 2.97to 12.57mmolg-1d-1,the average value was 5.98mmolg-1d-1,fluctuated mainly from 3.99 to5.28?molg-1d-1.The group with the highest methane oxidation rates of paddy soils were from Jiangjian Yangzhou(12.57mmolg-1d-1),Jiangjian Sanjiang(12.55mmolg-1d-1)Hubei Jingmen(8.38mmolg-1d-1)and Jiangsu Binhai(8.38mmolg-1d-1).The group with the lowest oxidation rate were soil from Hulan Gushi(4.47mmolg-1d-1),Hulan Taoyuan(3.99mmolg-1d-1)?Hainan(3.30mmolg-1d-1)and Sichuan Pengzhou(2.96mmolg-1d-1).(3)The results showed that the range of net nitrogen mineralization rate was 0.34-4.30?gg-1d-1,the average value was 1.23?gg-1d-1,fluctuated mainly 0.34-1.97?gg-1d-1.The group with the lower net nitrogen mineralization rate was 4.40?gg-1d-1in Ziyang,Sichuan,1.97?gg-1d-1in Yangzhou,Jiangsu and 1.97?gg-1d-1in Jiaxing,Zhejiang.The paddy soil in 4 cases was from Sichuan Yuanyang(0.44?gg-1d-1),Sichuan Dazhou(0.43?gg-1d-1),Heilongjiang Hailun(0.35?gg-1d-1)and Jiangsu Binhai(0.34?gg-1d-1).The change of soil respiration rate in24 typical paddy fields was consistent with the change of mineralization rate.(4)Twenty-four typical paddy soils were washed to remove inorganic nitrogen,and then incubation experiments were carried out to study nitrogen fixation using13C and15N isotope tracer conditions.It was found that the soil consumption of13CH4was accompanied by a significant increase in the abundance of15N2indicating that methane oxidation and biological nitrogen fixation were coupled.Paddy soil with low nitrogen mineralization rate showed high nitrogen fixation activity.By evaluating13CH4concentration,15N abundance,methane oxidation rate and net nitrogen mineralization rate,seven out of twenty-four paddy soils were selected,and they were Jingmen soil from Hubei Province,Leizhou soil from Guangdong Province,Hailun soil from Heilongjiang Province,Jiansanjiang soil from Heilongjiang province,Yingtan soil from Jiangxi province,Taoyuan soil from Hunan province and Yubei soil from Chongqing city.(5)After removing the background inorganic nitrogen from the selected 7 cases of rice soil,the potential characteristics of nitrogen fixation under different methane substrate concentrations were studied by using13C and15N isotope tracers.The results showed that the rice soils of Jingmen in Hubei province,Jiansanjiang and Hailun in Heilongjiang province started the biological nitrogen fixation process under the condition of 15%methane concentration,and the rice soils of Leizhou in Guangdong province,Yingtan in Jiangxi province,Taoyuan in Hunan province and Yubei in Chongqing provincewere able to perform the biological nitrogen fixation under the condition of 30%methane concentration.The results showed that the high concentration of methane substrate was beneficial to the biological nitrogen fixation process of aerobic methane oxidation in rice soil,and the coupling of methane oxidation with biological nitrogen fixation had a certain concentration limit of methane substrate.In summary,this experiment shows that methane aerobic oxidation in rice soil can drive the biological nitrogen fixation process,and the rice soil with low nitrogen mineralization rate is advantageous to biological nitrogen fixation,while the high concentration of methane substrate is advantageous to the biological nitrogen fixation process.These results are of great significance for methane emission reduction in rice fields.
Keywords/Search Tags:paddy soil, methane oxidation, biological nitrogen fixation, net nitrogen mineralization, coupling mechanism
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