Integrated impacts of land use intensification on greenhouse gas emissions and soil microbial communities in the Taihu Lake Region: patterns, mechanisms, and implications

ABSTRACT The Taihu Lake region has experienced rapid land use intensification, characterized by conversions from natural wetlands (NW) to conventional rice-wheat rotation fields (RW) and further to greenhouse vegetable fields (GH), driven by economic interests. While such transformations are widespread, their combined effects on greenhouse gas (GHG) emissions and underlying soil microbial mechanisms remain poorly understood. This integrated study addresses these gaps through multi-faceted analyses of GHG fluxes, soil microbial communities, and nitrogen (N)-cycling functional genes across NW, RW, and GH sites. Two-year in-situ field experiments revealed significant GHG emission shifts: land use intensification reduced methane (CH₄) emissions (NW: 970.66 ± 100.09 kg C ha⁻¹; RW: 896.71 ± 300.44 kg C ha⁻¹; GH: 71.23 ± 63.62 kg C ha⁻¹) but markedly increased nitrous oxide (N₂O) emissions (NW: 3.35 ± 0.44 kg N ha⁻¹; RW: 14.38 ± 4.09 kg N ha⁻¹; GH: 81.62 ± 4.89 kg N ha⁻¹). Global warming potential followed the order RW > NW > GH, indicating intensified comprehensive greenhouse effects during NW→RW conversion and mitigation during RW→GH conversion. Microbial community analyses showed land use intensification directly altered bacterial and fungal compositions, with stronger impacts on bacteria. Bacterial communities correlated closely with soil NO₃⁻-N, pH, and electrical conductivity, exhibiting decreased deterministic processes (opposite to fungi). Arable lands (RW/GH) displayed more complex microbial networks, and seasonal variations (notably summer) influenced microbial diversity and function, though less strongly than land use effects. Integrating quantitative PCR and metagenomics uncovered microbial mechanisms driving N₂O emissions: intensification reshaped N-cycling microbial communities, depleting nitrogen fixation, dissimilatory nitrate reduction to ammonium, and anammox marker genes in GH soils. Denitrifying communities segregated similarly to total N-cycling assemblages, with increased network complexity but divergent stability. Critically, intensification amplified N₂O emission potential by elevating Pseudomonadota harboring nirK/norB genes (and associated communities) while reducing nosZ (encoding N₂O reductase) abundance—directly linking microbial functional imbalance to emission increases. Collectively, this study demonstrates that land use intensification in the Taihu Lake region drives GHG emission trade-offs (reduced CH₄ but amplified N₂O) and restructures soil microbial communities and N-cycling functions. These findings highlight the need to prioritize microbial functional balance (e.g., restoring nosZ-carrying taxa) in mitigation strategies, providing critical insights for sustainable land management in wetland-agricultural transition zones. Acknowledgment This study was funded by the National Key Research and Development Program of China (2023YFF0805403, 2025YFD1700403) and National Natural Science Foundation of China (42377311).