Interactions between methanotrophs and ammonia oxidizers modulate the response of in situ methane emissions to simulated climate change and its legacy in an acidic soil

Abstract

Methane (CH₄) is one of the most important greenhouse gases which can be formed by methanogens and oxidized by methanotrophs, as well as ammonia oxidizers. Agricultural soils can be both a source and sink for atmospheric CH₄. However, it is unclear how climate change, will affect CH₄ emissions and the underlying functional guilds. In this field study, we determined the impact of simulated climate change (a warmer and drier condition) and its legacy effect on CH₄ emissions and the methanogenic and methanotrophic communities, as well as their relationships with ammonia oxidizers in an acidic soil with urea application. The climate change conditions were simulated in a greenhouse, and the legacy effect was simulated by removing the greenhouse after twelve months. Simulated climate change significantly decreased the in situ CH₄ emissions in the urea-treated soils while the legacy effect significantly decreased the in situ CH₄ emissions in the control plots, but had very little effect in the urea-treated soils. This indicates that the impact of simulated climate change and its legacy on CH₄ emissions was significantly modified by nitrogen fertilization. Methanotrophs were more sensitive than methanogens in response to simulated climate change and its legacy effect, especially in the urea treated soil. Significant negative correlations were observed between the abundances of ammonia oxidizers and methanotrophs. Additionally, results of partial least path modeling (PLS-PM) indicated that the interactions of methanogens and methanotrophs with ammonia oxidizing archaea (AOA) had significant positive relationships with in situ CH₄ emissions under the simulated climate change condition. Our work highlights the important role of AOA for CH₄ emissions under climate change conditions. Further research is needed to better understand this effect in other ecosystems.