Soil Methanogen and Methanotroph Communities of Four Land Use Types in Dongting Lake Area: Linkages with Potential Methane Production

Methane (CH4) emissions are regulated by the balance between CH4 production and oxidation, which are mediated by methanogens and methanotrophs. Little is known about the key drivers of potential methane production (PMP) under different land use types in the Dongting Lake area. This study investigated four land use types (natural wetland, poplar plantation, rice cropland, and vegetable field) in the Dongting Lake area. The effects of land use types on (a) the abundances and community compositions of soil methanogens and methanotrophs and (b) soil potential methane production were investigated. The results showed that the soil potential methane production of the rice cropland (0.26 ± 0.02 µg g−1 h−1) and vegetable field (0.26 ± 0.01 µg g−1 h−1) was higher than that of the poplar plantation (0.16 ± 0.01 µg g−1 h−1). The compositions of methanogenic and methanotrophic communities varied in response to different land uses. The mcrA gene abundance in the rice cropland (0.84 ± 0.05 × 108 copies/g) and vegetable fields (1.23 ± 0.15 × 108 copies g−1) was higher than that in the natural wetland (0.09 ± 0.01 × 108 copies g−1) and poplar plantation (0.08 ± 0.03 × 108 copies g−1). The pmoA gene abundances in the rice cropland (1.65 ± 0.08 × 108 copies g−1) and vegetable fields (1.88 ± 0.32 × 108 copies g−1) were higher than those in the natural wetland (0.16 ± 0.02 × 108 copies g−1) and poplar plantation (0.11 ± 0.03 × 108 copies g−1). In addition, both pmoA and mcrA gene abundances were positively correlated with potential methane production. However, the regression line between pmoA gene abundance and potential methane production showed a shallower slope than that between mcrA gene abundance and potential methane production. These results suggest that soil potential methane production was primarily driven by increased methanogenesis rather than reduced methane oxidation. In addition, soil organic carbon, total nitrogen, water content, and pH were key abiotic factors regulating potential methane production and the abundance and community compositions of methanogens and methanotrophs in the Dongting Lake area.