Characterizing Spatiotemporal Dynamics of CH₄ Fluxes from Rice Paddies of Cold Region in Heilongjiang Province under Climate Change.

Paddy fields have become a major global anthropogenic CH₄ emission source, and climate change affects CH₄ emissions from paddy ecosystems by changing crop growth and the soil environment. It has been recognized that Heilongjiang Province has become an important source of CH₄ emission due to its dramatically increased rice planting area, while less attention has been paid to characterize the effects of climate change on the spatiotemporal dynamics of CH₄ fluxes. In this study, we used the calibrated and validated Long Ashton Research Station Weather Generator (LARS-WG) model and DeNitrification-DeComposition (DNDC) model to simulate historical and future CH₄ fluxes under RCP 4.5 and RCP 8.5 of four global climate models (GCMs) in Heilongjiang Province. During 1960⁻2015, the average CH₄ fluxes and climatic tendencies were 145.56 kg C/ha and 11.88 kg C/ha/(10a), respectively. Spatially, the CH₄ fluxes showed a decreasing trend from west to east, and the climatic tendencies in the northern and western parts were higher. During 2021⁻2080, the annual average CH₄ fluxes under RCP 4.5 and RCP 8.5 were predicted to be 213.46 kg C/ha and 252.19 kg C/ha, respectively, and their spatial distributions were similar to the historical distribution. The average climatic tendencies were 13.40 kg C/ha/(10a) and 29.86 kg C/ha/(10a), respectively, which decreased from west to east. The simulation scenario analysis showed that atmospheric CO₂ concentration and temperature affected CH₄ fluxes by changing soil organic carbon (SOC) content and plant biomass. This study indicated that a paddy ecosystem in a cold region is an important part of China's greenhouse gas emission inventory in future scenarios.