冻土区土壤氧化亚氮排放:研究进展与展望

Nitrous Oxide Emissions from Permafrost Regions: Progresses and Prospects

  • 摘要: 气候变暖会促进土壤氧化亚氮(N2O)等温室气体排放,进而加剧冻土区非碳−气候反馈。尽管北半球近1/4的陆地表面被冻土覆盖,但目前研究对冻土区土壤N2O产生−累积−扩散−释放过程与调控机制的认识还十分有限。通过梳理以往的研究,本文详细阐述了N2O产生的过程机理,系统分析了差异化的观测方案以及N2O分析方法(地表通量和剖面浓度),深入讨论了融化期N2O脉冲排放存在的争议、N2O通量日变化模式及其驱动因素、土壤剖面N2O浓度变化特征及其来源、植物生长对土壤N2O排放的影响等。未来应加强N2O通量观测方法的误差评估和增加非生长季地表通量/剖面浓度的观测频率,并合理利用同位素和分子生物学等新技术,明确土壤冻融过程触发和主导N2O排放的过程机制以及冻融期脉冲排放对年累积通量的贡献,旨在为后续观测方法优化以及探究冻融期N2O排放的生物和物理过程机制提供理论支撑。

     

    Abstract: Climate warming promotes the emission of greenhouse gases (GHGs), such as nitrous oxide (N2O) from soils while exacerbating non-carbon-climate feedbacks in the permafrost zone. Although nearly 1/4 of the land surface in the Northern Hemisphere is covered by permafrost, current research remains constrained in its understanding of the production, accumulation, diffusion and release processes of N2O from permafrost-affected soils, along with the associated regulatory mechanisms. In this sammary, the mechanisms of the N2O generation process were thoroughly examined by synthesizing previous research findings. The differentiated observational schemes, including N2O analysis methods (surface flux and profile concentration), were systematically evaluated. Additionally, this sammary addressed the controversy surrounding N2O pulse emissions during the thawing period, the patterns of daily changes in N2O flux and their driving factors, the characteristics of variations in N2O concentration in the soil profile and its sources, and the effects of plant growth on soil N2O emissions. In the future, we should strengthen the error assessment of N2O flux observation methods, increase the observation frequency of surface flux and profile concentration during the non-growing season, and make effective use of new techniques such as isotopic analysis and molecular biology to elucidate the mechanisms underlying N2O emissions triggered by soil freezing and thawing. Additionally, we should assess the contribution of pulsed emissions to the annual cumulative fluxes during freezing and thawing periods, to provide theoretical support for optimizing the specifications of observation methods and investigating the biological and physical mechanisms of N2O emissions during these critical periods.

     

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