放牧草地氧化亚氮排放：研究进展与展望

氧化亚氮(N2O)是一种长寿命、高辐射效率的温室气体,草地是其重要的自然排放源,放牧活动和气候变化剧烈影响草地排放特征与强度,排放通量测量误差、研究对象的局限、关键过程影响不清等因素限制了对草地排放总量和氮气候反馈效应的准确评估。本文讨论了差异化的观测方案包括N2O浓度分析方法和采样频率可能给草地排放量估算造成的影响;指出研究放牧草地N2O排放,应综合考虑放牧相关排放源的贡献,定量整个放牧系统的排放量;提出气候变化影响程度取决于气候因子是否能够缓解放牧草地土壤“贫氮”对N2O生产的限制。未来应加强观测方法的误差评估和非生长季通量观测的频率,明确土壤冻融过程触发和主导N2O排放的机制以及冻融期脉冲排放对国家尺度排放的贡献,了解多年冻土区高寒草地N2O排放水平及其对全球变暖的响应,探明大气氮干沉降增加及干沉降组分变化对草地排放的影响。

Nitrous oxide emissions from grazed grasslands in China: Progresses and prospects

Nitrous oxide(N₂O)is a long-lived greenhouse gas with a high radiation efficiency. Grasslands are important natural sources of N₂O. Grazing and climate change intensively influence N₂O emissions from grasslands in China. Deficiencies on the measuring methods, the integrality of study, and the research of key processes, e.g. soil freeze-thaw cycles, cause huge uncertainties on the estimates of grassland N₂O emissions and grassland nitrogen(N)feedback on climate change. In this study, we analyzed the possible influences of measuring methods, including the analysis method of N₂O concentrations by gas chromatography and the sampling frequency, on the quantification of N₂O emissions from grasslands; emphasized the importance of grazing-related sources, e.g. dung and urine patches on grasslands, livestock night barns, and forage croplands,on the budget of regional N₂O emissions from grasslands; revealed the determinant of climate change influencing N₂O emissions from grasslands, namely, the limitation of low N substrate availability on microbial N₂O production in soils. The future research should focus on the evaluation of measurement errors induced by the observation methods, the importance of high-frequency measurements during the non-growing season on the quantification of annual total emissions, the triggering mechanisms of freeze-thaw-related N₂O emissions, and the contribution of pulsed N₂O emissions during the freeze-thaw period to the national emission inventory in grasslands, the responses of N₂O emissions from alpine grasslands to changing climate change, and the impacts of increased dry N deposition and changing N components in the deposition on grassland N₂O emissions.