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: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=667939
• 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（N2 O）和二氧化碳（CO2）的重要排放源，这些排放与种植系统的氮和碳输入有关。我的计划的长期目标是验证和修改模型预测从农业生态系统的净温室气体通量，并确定土壤和作物的可持续农业生态系统的管理措施。* 在寒冷地区，由于土壤冻融（FT）事件，农业土壤的N2 O年排放量有一半以上可能发生在生长季节之外。季节性冻土与大面积的集约种植相吻合，但对FT引起的N2 O排放的研究有限。这是因为N2 O排放在时间和空间上变化很大，对典型的测量方法提出了挑战，特别是在寒冷地区。* 我的研究小组是世界上少数几个使用微气象技术解决这一挑战的研究小组之一。在我们的长期研究现场，我们观察到，在非生长季节，管理的差异往往是最普遍的，但我们还没有确定的根本原因，导致大量的FT N2 O排放在一系列条件。如果理解了这些差异，那么就可以设计减少解冻时N2 O排放的做法。本研究的主要目的是：1）定量研究不同土壤和作物管理条件下农田生态系统CO2和N2 O通量的大小和时间动态，2）评价冬季变暖对两种土壤类型非生长季N2 O通量的影响，3）研究FT诱导的多年生和一年生作物N2 O通量的差异。4）比较不同土壤类型中FT和干湿循环N2 O排放增强的潜在因素; 5）改进基于过程和经验模型的FT诱导N2 O通量预测。* 我提出了多种方法的组合：1）在对加拿大重要的农业地区进行微气象实验，在使用全年微气象方法之前尚未进行过研究; 2）冬季变暖的新型高精度称重土壤蒸渗仪; 3）使用经过FT和干湿循环的土柱进行实验室实验，以控制影响排放的驱动因素。可调谐二极管激光示踪气体和傅里叶变换红外分析将与测微计或自动室相结合，以高时间分辨率测量气体通量。FT事件和增强的微生物过程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）进行表征。将与政府科学家合作改进基于过程的模型。 6名研究生和10名本科生将在这种刺激的环境中接受培训。研究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。