Improved Understanding of Nitrous Oxide Emissions from Seasonally Frozen Cropland for Mitigation of Agricultural Greenhouse Gas Emissions

提高对季节性冻结农田一氧化二氮排放的了解，以减少农业温室气体排放

• 批准号: RGPIN-2017-04582
• 负责人: WagnerRiddle, Claudia
• 金额: $ 4.23万
• 依托单位: University of Guelph
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=711136
• 关键词: Improved; Understanding; Nitrous; Oxide; Emissions

Agricultural soils are significant emitters of the greenhouse gases nitrous oxide (N2O) and carbon dioxide (CO2) and these emissions are related to nitrogen and carbon inputs of cropping systems. The long-term objectives of my program are to validate and modify models predicting net GHG fluxes from agro-ecosystems and to identify soil and crop management practices for sustainable agro-ecosystems. In cold regions more than half of annual N2O emissions for agricultural soils can occur outside the growing season due to soil freeze-thaw (FT) events. Seasonally frozen land coincides with large areas of intensive cropping, but research into FT-induced N2O emissions has been limited. This is because N2O emissions are highly variable in time and space and present a challenge for typical measurement methods, particularly in cold regions. My research group is one of few in the world using micrometeorological techniques addressing this challenge. At our long-term study site, we have observed that differences in management are often most prevalent during the non-growing season, but we have not identified the underlying causes leading to large FT N2O emissions in a range of conditions. If these differences are understood, then practices for reduced N2O emissions at thaw could be designed. The objectives of this proposal are: 1) to quantify the magnitude and temporal dynamics of CO2 and N2O fluxes from agro-ecosystems under soil and crop management that result in contrasting FT conditions; 2) to evaluate the effect of winter warming on non-growing season N2O fluxes on two soil types; 3) to investigate the differences in FT-induced N2O between perennial and annual crops; 4) to compare the underlying factors for enhanced N2O emissions in FT and dry-wet cycles in a range of soil types; and 5) to improve the prediction of FT-induced N2O fluxes in process-based and empirical models. I propose a combination of approaches: 1) micrometeorological experiments in an agricultural area of importance for Canada, that has not been studied before using year-round micromet methods; 2) new high-precision weighing soil lysimeters with winter warming; 3) laboratory experiments using soil columns subjected to FT and dry-wet cycles to control drivers affecting emissions. Tunable diode laser trace gas and Fourier Transform Infra-red analyses will be coupled with micromet or automatic chambers to measure gas fluxes at high temporal resolution. Carbon and nitrogen substrates released by FT events and enhanced microbial processes will be characterized through sophisticated techniques (e.g. NMR, molecular microbial analysis). Process-based models will be improved in collaboration with government scientists. Six graduate and 10 undergraduate students will be trained in this stimulating environment. Findings will have a significant impact on Canada's ability to predict agricultural GHG emissions.

农业土壤是温室气体一氧化二氮（N2O）和二氧化碳（CO2）的重要发射剂，这些排放量与农作物系统的氮和碳输入有关。我计划的长期目标是验证和修改模型，以预测农业生态系统的净温室气通量，并确定可持续农业生态系统的土壤和作物管理实践。 在寒冷地区，由于土壤冷冻率（FT）事件，可能发生在生长季节之外的农业土壤年度N2O排放中一半以上。季节性冷冻的土地与大量的密集种植相吻合，但是对FT引起的N2O排放的研究一直有限。这是因为N2O排放在时间和空间上是高度可变的，并且对典型的测量方法（尤其是在冷区域中）提出了挑战。 我的研究小组是世界上少数几个针对这一挑战的微气流技术之一。在我们的长期研究地点，我们观察到，在非生长季节，管理差异通常最为普遍，但是我们尚未确定导致大量FT N2O在一系列条件下的基本原因。如果了解这些差异，则可以设计减少N2O排放的实践。 该提案的目标是：1）量化在土壤和农作物管理下，来自农业生态系统的二氧化碳和N2O通量的幅度和时间动力学，从而导致FT条件相比； 2）评估冬季变暖对非生长季节N2O通量对两种土壤类型的影响； 3）研究多年生作物和年度农作物之间FT诱导的N2O的差异； 4）比较在一系列土壤类型中，FT和干湿周期增强的N2O排放的基本因素； 5）在基于过程和经验模型中改善FT诱导的N2O通量的预测。 我提出了一种方法的组合：1）在加拿大重要性的农业领域中的微气流实验，在使用全年微测方法之前尚未对此进行研究； 2）新的高精度称重土壤测量器，冬季变暖； 3）实验室实验，使用经受FT和干湿周期的土壤柱进行控制，以控制影响排放的驱动因素。可调二极管激光痕量气体和傅立叶变换式红外分析将与微孔或自动室结合，以高时间分辨率测量气体通量。 FT事件释放的碳和氮底物将通过复杂的技术（例如NMR，分子微生物分析）来表征。基于过程的模型将与政府科学家合作改善。 在这个刺激的环境中，将对六名毕业生和10名本科生进行培训。调查结果将对加拿大预测农业温室气体排放的能力产生重大影响。