Reduction of soil methane emissions from croplands with 20–40 years of cultivation mediated by methane-metabolizing microorganisms

Reducing carbon emissions from cropland ecosystems is an important measure to achieve early carbon neutrality. However, how methane-metabolizing microorganisms affect methane emissions from cropland soils of different planting years is not known. In this study, we determined methane emissions from cropland soils of different tobacco-rice rotation years after rice harvesting. By mean of functional gene sequencing, we analyzed the relationship between methane-metabolizing microorganisms and methane emissions, and revealed the microbial mechanism of action for methane emissions from cropland soils. The results showed that the soil organic carbon content was higher (P < 0.05) and methane emissions were lower (P < 0.05) in cropland cultivated for 20–40 years (PY20). Soil methane emissions from PY20 cropland were reduced by 30.11% and 14.58% (P < 0.05) compared to cropland planted for 10–20 years and more than 40 years. The alpha diversity of methanogens communities was significantly lower in PY20 cropland soils, whereas the methanotrophs communities alpha diversity did not differ significantly between planting years. The methanogenic genus Methanocorpusculum was significantly and positively correlated with methane emissions. The relative abundance of Methanocorpusculum in PY20 cropland soil was lower (P < 0.05), and the relative abundance of Methycystis, a type II methanotrophs with greater oxidizing capacity for methane, was higher (P < 0.05). Reducing PY20 cropland soil methane emissions by reducing methane production and enhancing methane oxidation. At the same time, more methanotrophs in PY20 cropland soil formed a molecular interactions network with methanogens. Planting years altered the diversity and composition of methane-metabolizing microbial communities and the interactions of different taxa, which in turn affected methane emissions. Cropland soils that have been cultivated for 20–40 years have lower methane production capacity and higher methane oxidation capacity, resulting in lower methane emissions. This study provides a scientific reference for the microbial action mechanism of soil methane emission from cropland under different planting years, with a view to contributing to carbon neutralization in cropland ecosystems.