东北黑土地区稻田甲烷排放时空演变及排放潜力分析

稻田甲烷排放是农业源甲烷排放的主要来源。东北黑土地区是我国最大的粮食生产基地,农业温室气体减排是实现黑土地永续利用的关键议题之一。运用稻田甲烷排放模型(CH4MOD)核算并分析了2009-2018年东北黑土地区稻田甲烷排放的时空演变特征,结合GOSAT卫星遥感数据探究了水稻生产与区域甲烷排放的时空动态联系,进一步量化了稻田甲烷对区域甲烷排放的贡献程度及不同情景下的排放潜力。结果表明,受水稻生产面积扩张和排放强度提高的影响,东北黑土地区稻田甲烷排放总量从2009年的39.05万t增加到2018年的79.53万t。东北黑土地区区域甲烷排放在季节变化和栅格单元上表现出与稻田甲烷排放较为一致的时空动态,大规模的稻田耕作可能会增加水稻生产与区域甲烷排放直接相关的可能性。随着水稻持续扩种稳产,2018年东北黑土地区水稻生产贡献了区域甲烷排放总量的15.04%,其中黑龙江省的贡献率高达31.06%。在基准发展情景下,预计2035年东北黑土地区稻田CH₄排放量较2018年增加19.5%;在粮食供给保障情景下,维持当前稻田耕作面积,水稻生产集约化程度提高,预计其稻田CH₄排放量较2018年减少0.88%;在此基础上,采取促进秸秆还田、增施有机肥、实施节水间歇灌溉等稻田管理措施将使稻田CH₄排放量增加17.8%-63.6%。以满足膳食需求和供给保障为导向,优化水稻种植结构、控制稻田耕作面积,推动技术进步、品种改良以提升单产水平,采取化肥和有机肥搭配施用、节水间歇灌溉等途径能够缓解稻田甲烷排放。研究综合运用自上而下的遥感数据和自下而上的模型运算,刻画了水稻生产与区域甲烷排放的时空联系,进一步评估了稻田甲烷的排放潜力及减排措施的减排效果,为促进东北黑土地区农业甲烷减排和生产布局优化提供了理论依据和决策参考。

Spatiotemporal evolution and potential prediction of methane emission from paddy fields in the black soil region of Northeast China

Emission from paddy fields is a major source of agricultural methane emissions. The black soil region of Northeast China (BSRNC) is the largest grain production base, where reducing greenhouse gas emission of agricultural sector is a crucial issue for sustainable utilization of black soil land. In this study, we used CH4MOD model to analyze the spatiotemporal evolution of methane emission from paddy fields in the BSRNC from 2009 to 2018, then explored the spatiotemporal dynamic relationship between rice production and regional methane emission based on remote sensing data of GOSAT satellite, and further clarified the contribution and potential of methane emission from paddy fields. The results showed that due to the expansion of rice production area and the increase of emission intensity, methane emission from paddy fields in the BSRNC increased from 3.905×10⁵ tons to 7.953×10⁵ tons. Regional methane emission showed a spatiotemporal dynamic that was consistent with methane emission from paddy fields in terms of seasonal variation and grid scale. Large-scale paddy cultivation might increase the possibility that rice production directly related to regional methane emissions. With the continuous area expansion and increasing yield, emission from paddy fields contributed 15.04% of regional methane emission in 2018, which was as high as 31.06% in Heilongjiang Province. Under the baseline development scenario, CH₄ emissions from paddy fields in the BSRNC were expected to increase by 19.5% in 2035 compared with that in 2018. Under the food supply security scenario, the current paddy field cultivation area is maintained, the degree of rice production intensification is increased, and the CH₄ emission from paddy field is expected to decrease by 0.88% compared with that in 2018. On the basis of food supply security scenario, the CH₄ emission from paddy fields is expected to increase by 17.8%-63.6% by adopting paddy field management measures, such as straw returning to the field, increasing the application of organic fertilizer and implementing water-saving intermittent irrigation. This can be alleviated by emission reduction measures that guided by the guarantee of food supply, such as the optimization of rice planting structure, the control of paddy cultivation area, the promotion of technological progress and variety improvement to improve the yield level, the combination of fertilizer and organic fertilizer application, water-saving intermittent irrigation and other ways. The study comprehensively used top-down method (calculation based on GOSAT data) and bottom-up model (CH4MOD model) to depict the spatiotemporal relationship between rice production and regional methane emission, further evaluated the potential of paddy methane emission and the effect of emission reduction measures. It can provide theoretical basis for reducing agricultural methane emission and optimizing cultivating layout in the black soil region of Northeast China.