Potential mechanistic shifts in carbonaceous greenhouse gas dynamics and mitigation implications in ameliorated...

Ecological restoration of soda saline-alkali soils is critical for synergizing food security with climate change mitigation; however, the coupling mechanisms between soil carbon cycling and carbonaceous greenhouse gas dynamics during amelioration remain obscure. This study conducted a field experiment in the soda saline-alkali region of Northeast China to investigate the responses of the soil-plant-microbe system and carbonaceous greenhouse gas driving mechanisms under uncultivated wasteland (WL), conventional paddy (CK), and organically amended paddy field (PF). The results throughout the entire 2023 growing season indicated that the amendment significantly reduced soil pH by 3.66% (down to 8.68) and electrical conductivity by 77.28% (down to 0.333 mS cm^-1) relative to CK via a "Ca-Na displacement" mechanism, alleviating osmotic stress and boosting soil organic carbon (SOC) accumulation (an increase of 49%-135%, peaking at 10.132 g kg^-1) and carbon cycling enzyme activities. The PF treatment reduced CO₂ emissions (averaging 27.55% lower than WL, with the peak limited to 1097.26 mg m^-3), but conversely resulted in elevated CH₄ concentrations (an average increase of 30.98% relative to WL, peaking at 996 mg m^-3). Furthermore, multivariate explanation and variance decomposition analysis suggested a potential transition in carbonaceous greenhouse gas regulation: the ecosystem transitioned from a plant-dependent transport pathway under saline constraints (CK, dominated by plant biomass transport) to a substrate-enzyme coupled regulation pathway following amelioration (PF, dominated by carbon fractions and enzyme activities). Consequently, a preliminary stratified low-carbon management strategy is proposed: prioritizing salt-tolerant varieties with developed aerenchyma for unameliorated soils, while implementing precision regulation of carbon substrates and water for reclaimed fertile soils to balance productivity with environmental footprints.