Combined Effects of Drying-Rewetting and Ammonium Addition on Methanotrophs in Agricultural Soil: A Microcosm Study

Oxidation of methane by soil microorganisms is an important mechanism controlling the content of this potent greenhouse gas in the atmosphere. Agricultural soils operate under stressful conditions, and ammonium (N-fertilization) and drying (global warming) may have a significant impact on the methane oxidation. In order to investigate how soil methanotrophs respond to drying-rewetting (DW), ammonium addition (100 mg/g) (A) and their combined action (MS), agricultural soil microcosms were incubated over the three months and methane oxidation was measured before and after perturbations, while community composition was monitoring using the 16S rRNA gene sequencing. A significant decline in the methane-oxidation activity after perturbations was found, with subsequent restoration, and the combined treatment was more effective than the sum of individual treatments, indicating a synergistic effect. After rewetting the structure of the bacterial community returned to pre-dry-down levels, but the application of ammoni