Nutrient Legacies and Time Lags: Understanding Catchment Biogeochemical Responses in Anthropogenic Landscapes

与高水平化肥使用和集中畜牧作业相关的过量营养物质进入地下水和地表水，导致缺氧、水生生物毒性和饮用水污染问题。减少化肥使用量或实施其他最佳管理措施(BMP)是为了改善水质，但它们往往不能产生预期的结果。这种缺乏反应的情况被归因于遗留商店的积累，这可能导致BMP实施和水质改善之间存在很大的时间滞后。了解人类遗产的积累和枯竭如何改变水质是我研究计划的重点。这项研究不仅解决了全球营养收支中的一个关键缺口，而且还有助于创建一个实用的框架，为水质管理设定现实的、具体时间的目标。*Discovery研究将以我最近的工作为基础，该工作提供了农业土壤中有机氮(N)积累的新证据，并提出了关于N遗留在流域尺度N动态中的作用的重要问题：(1)什么机制控制农业景观中遗留N的积累和消耗？(2)这种遗留如何导致管理实践的变化和水质改善之间的时间滞后？*在拟议的工作中，将开发一个模型来探索关于土壤碳-氮动态的假设，并阐明对N积累和消耗的控制。该模型将使用现有数据集和特定于项目的实地工作进行验证。在哈罗农业研究站的协作工作中，将在一系列化肥处理下确定遗留氮素随深度的积累，并将使用同位素分析来检测排水中硝酸盐的来源。此外，将在已确定的时间序列上进行实地研究，以确定农地退役后的N浓度轨迹。这样开发的包气地带遗留模型将在空间上明确的框架中使用，以量化加拿大国内外流域从地块到田野到集水区的一系列尺度的时间滞后。这将为对沿海水域营养物质负荷中与遗产相关的时间滞后的作用进行更全球范围的分析奠定基础。*由发现号资助的研究将增加对人类景观中N个遗产及其对水质影响的基本了解。该项目将利用现有大学在水和生态水文学方面的优势，通过培训水和环境部门的顶级HQP，为加拿大经济做出积极贡献。研究成果将对分水岭尺度的营养物质传输领域做出重大贡献，从而使加拿大水资源能够更有效地管理。

Excess nutrients associated with high levels of fertilizer application and concentrated livestock operations find their way into both ground and surface waters, leading to problems of hypoxia, aquatic toxicity and drinking water contamination. Reductions in fertilizer application or implementation of other best management practices (BMPs) have been carried out to improve water quality, but often they do not yield expected results. Such lack of response is attributed to buildups of legacy stores that can cause significant time lags between BMP implementation and water quality improvements. Understanding how the accumulation and depletion of anthropogenic legacies alter water quality is the focus of my research program. The research not only addresses a critical gap in global nutrient budgets, but also helps to create a practical framework for setting realistic, time-specific goals for water quality management. ***The Discovery research will build on my recent work, which provides new evidence of organic nitrogen (N) accumulation in agricultural soils and raises important questions regarding the role of N legacy in catchment-scale N dynamics: (1) What mechanisms control legacy N accumulation and depletion within agricultural landscapes? (2) How do such legacies contribute to time lags between changes in management practices and improvements in water quality? ***In the proposed work, a model will be developed to explore hypotheses regarding soil carbon-nitrogen dynamics and to clarify controls on N accumulation and depletion. The model will be validated using both existing datasets and project-specific fieldwork. In collaborative work at the Harrow Agricultural Research Station, depth-dependent accumulation of legacy N will be determined under a range of fertilizer treatments, and isotope analysis will be used for source detection of nitrate in drainage water. In addition, field studies will be carried out across an identified chronosequence to determine N concentration trajectories after agricultural land retirement. The vadose zone legacy model thus developed will be used in a spatially explicit framework to quantify time lags at a range of scales, from plot to field to catchment, for watersheds both within and outside Canada. This will lay the groundwork for a more global-scale analysis of the role of legacy-related time lags in nutrient loading to coastal waters. *** Research funded through the Discovery will increase fundamental understanding of N legacies in anthropogenic landscapes and their impacts on water quality. The project will leverage existing university strengths in water and ecohydrology and contribute positively to Canada's economy by training of top HQP in the water and environmental sector. Research results will contribute significantly to the field of watershed-scale nutrient transport, thus allowing for more effective management of Canadian Water Resources.***********