Long-term nitrogen and phosphorus fertilization modulates methane uptake and microbial community dynamics in subtropical forest soils

Subtropical forests play a crucial role in reducing atmospheric methane (CH₄) levels; however, how long-term nitrogen and phosphorus enrichment regulates CH₄ uptake at low CH₄ levels remains poorly understood. This study combined laboratory microcosms, CH₄ uptake potential measurements, DNA-stable isotope probing, quantitative polymerase chain reaction, and Illumina sequencing of 16S rRNA gene to assess atmospheric CH₄ uptake at low levels of CH₄ and the dynamics of CH₄-consuming communities in subtropical forest soils under long-term nitrogen and phosphorus fertilization. While three-month microcosm incubation did not reveal consistent patterns in CH₄ uptake with nitrogen fertilization, the increase in phosphate (PO₄3-) availability stimulated CH₄ uptake, suggesting alleviation of phosphorus limitation. The abundance of upland soil cluster α methanotrophs, crucial for atmospheric CH₄ uptake, exhibited sensitivity to high nitrogen levels, potentially influencing CH₄ dynamics in the forest ecosystems. Furthermore, the genus Methylocystis was identified as the predominant active methanotroph in the plots with high nitrogen and phosphorus levels, suggesting its adaptation to metabolize atmospheric CH₄ under nutrient-rich conditions. These findings underscore the complex interplay between nutrient availability, microbial communities, and atmospheric CH₄ dynamics in subtropical forest soils under ongoing nutrient deposition. Further studies are needed to investigate the underlying mechanisms and their implications for ecosystem functions.