Effects Of Silicon Application On Aerobic / Anaerobic Oxidation Of Methane In Paddy Fields Under Nighttime Warming Conditions

Paddy fields are an important source of methane emissions,and methane oxidation is an important methane reduction process.According to whether oxygen is used as an electron acceptor,methane oxidation is divided into aerobic methane oxidation（AMO）and anaerobic methane oxidation（ANMO）.At present,researchers mainly focus on NO₂^-/NO₃^-,SO₄^2--dependent anaerobic methane oxidation.In this paper,stable isotope labeling and molecular biology methods were used to analyze the changes in aerobic/anaerobic methane oxidation potential of rice fields under nighttime warming and silicon application conditions.In addition,the number,community composition and diversity of aerobic and anaerobic methane oxidizing bacteria in rice fields were studied.DNA-SIP technology was further used to reveal the correlation between the aerobic oxidation rate of methane and functional microorganisms.The main conclusions are as follows:1.Through stable isotope labeling and quantitative PCR,the aerobic methane oxidation rate and the number of aerobic methane oxidizing bacteria in non-rhizosphere soil were generally higher than those in rhizosphere soil.And by the PCo A analysis of functional gene pmo A,it can be found that the diversity of microbial composition in rhizosphere soil and non-rhizosphere soil is significantly different.According to the relative abundance of aerobic methane oxidizing bacteria in situ soil,Type I Methylobacter is the dominant methane oxidizing bacteria in the rhizosphere soil,and Type II Methylocystis is the dominant methane oxidizing bacteria in the non-rhizosphere soil.Both silicon application and nighttime warming promote the growth of dominant aerobic methane oxidizing bacteria in rhizosphere soil and non-rhizosphere soil.According to DNA-SIP and illumina sequencing,after the high-concentration CH₄+O₂ incubation,the number of aerobic methane oxidizing bacteria reduced significantly;Methylobacter in Type Ia methane oxidizing bacteria increased significantly in rhizosphere soil,whereas the Type II Methylocystis increased significantly in non-rhizosphere soil.Aerobic methane oxidation rate was significantly positively correlated with the relative abundance of Type I methane oxidizing bacteria.In rhizosphere soil,type I methane oxidizing bacteria maintained an advantage,In non-rhizosphere soil,type I methane oxidizing bacteria grew rapidly and became dominant methane oxidizing bacteria.2.Stable isotope incubation experiments showed that NO₂^--dependent anaerobic methane oxidation potential was the highestunder nighttime warming treatment,and the lowest under silicon treatment.Quantitative PCR showed that number of M.oxyfera 16S r RNA gene is the highest in the nighttime warming plots,and the lowest in the silicon treatment plots.The average anaerobic methane oxidation rate displayed a significant positive correlation with the gene copy abundance of N-DAMO.This suggested that nighttime warming is beneficial to the growth of N-DAMO bacteria,and silicon application inhibits the growth of N-DAMO bacteria.3.Stable isotope incubation experiments showed that NO₃^--dependent anaerobic methane oxidation potential was the highest in the nighttime warming soil,and the lowest in the silicon treatment soil.Quantitative PCR showed that M.nitroreducens 16S r RNA gene copy number is the highest in the nighttime warming soil,and is the lowest in the silicon soil.The average anaerobic methane oxidation rate had a significant positive correlation with the16S r RNA abundance of Nr-DAMO bacteria.Nighttime warming is beneficial to the growth of Nr-DAMO bacteria,while silicon application inhibits the growth of Nr-DAMO bacteria.