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: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=690782
• 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) 的重要排放源，这些排放与耕作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预测农业生态系统净温室气体通量的模型，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，由于土壤冻融 (FT) 事件，农业土壤年氧化亚氮排放量的一半以上可能发生在生长季节之外。季节性冰冻土地与大面积集约化种植同时发生，但对 FT 引起的 N2O 排放的研究有限。这是因为 N2O 排放量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应对这一挑战的研究小组之一。在我们的长期研究地点，我们观察到管理差异往往在非生长季节最为普遍，但我们尚未确定在一系列条件下导致大量 FT N2O 排放的根本原因。如果理解了这些差异，那么就可以设计减少解冻时 N2O 排放的做法。***本提案的目标是：1) 量化土壤和作物管理下农业生态系统中 CO2 和 N2O 通量的大小和时间动态，从而产生对比的 FT 条件； 2）评估冬季变暖对两种土壤类型非生长季N2O通量的影响； 3）研究多年生作物和一年生作物之间FT诱导的N2O的差异； 4) 比较一系列土壤类型中 FT 和干湿循环中 N2O 排放增加的根本因素； 5) 改进基于过程和经验模型中 FT 引起的 N2O 通量的预测。 ***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，该实验在使用全年微气象方法之前尚未进行过研究； 2）新型高精度称重土壤蒸渗仪，具有冬季加温功能； 3) 实验室实验使用土柱进行 FT 和干湿循环来控制影响排放的驱动因素。可调谐二极管激光痕量气体和傅里叶变换红外分析将与微米或自动室相结合，以高时间分辨率测量气体通量。费托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（例如核磁共振、分子微生物分析）进行表征。基于过程的模型将与政府科学家合作得到改进。 六名研究生和十名本科生将在这个激动人心的环境中接受培训。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。