Effect of Dissolved Organic Matter (DOM) on Greenhouse Gas Emissions in Rice Varieties

Abstract

Rice paddy fields are importan t sources of atmospheric methane (CH 4 ), and nitrous oxide (N 2 O) . In our previous study, we found that greenhouse gas emissions varied among rice varieties. Dissolved organic matter (DOM) is one of the most reactive organic matter fractions in an ecosystem. However, the relation between greenhouse gas emissions and DOM propertie s among rice varieties in paddy fields remains unclear. Here, a two-year field experiment was conducted to investigate the dynamic changes in DOM characteristics in seven rice varieties and their relation to the CH 4 and N 2 O emissions. Among the seven rice varieties studied, those with lower DOC, NH 4 -N and NO 3 -N concentrations and higher dissolved phenol (DP) concentrations in DOM had lower CH 4 and N 2 O emissions. Structural equation modeling revealed that DOC and DP can indirectly regulate CH 4 emissions by influencing mcrA and pmoA gene abundance, and DOC also can indirect regulate N 2 O emissions by influencing AOB , nirS and nosZ gene abundance. Fourier transform infrared (FTIR) and t hree-dimensional fluorescence (EEM) spectroscopy analysis further indicated that DOM includes more O-H and C=O phenol and protein content. Tryptophan-like and tyrosine-like protein material could regulate CH 4 and N 2 O emissions, respectively, by influencing the abundance of microbial functional genes ( mcrA , pmoA , AOB , nirS and nosZ ). These results demonstrated that the differences in greenhouse gas emissions among different rice varieties were dependent on DOM properties and microbial abundance , providing a theoretical basis for mitigating greenhouse gas emissions in rice paddy fields.