Nitrogen addition decreases methane uptake caused by methanotroph and methanogen imbalances in a Moso bamboo forest

Forest soils play an important role in controlling global warming by reducing atmospheric methane (CH₄) concentrations. However, little attention has been paid to how nitrogen (N) deposition may alter microorganism communities that are related to the CH₄ cycle or CH₄ oxidation in subtropical forest soils. We investigated the effects of N addition (0, 30, 60, or 90 kg N ha^-1 yr^-1) on soil CH₄ flux and methanotroph and methanogen abundance, diversity, and community structure in a Moso bamboo (Phyllostachys edulis) forest in subtropical China. N addition significantly increased methanogen abundance but reduced both methanotroph and methanogen diversity. Methanotroph and methanogen community structures under the N deposition treatments were significantly different from those of the control. In N deposition treatments, the relative abundance of Methanoculleus was significantly lower than that in the control. Soil pH was the key factor regulating the changes in methanotroph and methanogen diversity and community structure. The CH₄ emission rate increased with N addition and was negatively correlated with both methanotroph and methanogen diversity but positively correlated with methanogen abundance. Overall, our results suggested that N deposition can suppress CH₄ uptake by altering methanotroph and methanogen abundance, diversity, and community structure in subtropical Moso bamboo forest soils.