Reactive interfaces in agroecosystems: quantifying coupled biogeochemical dynamics across scales using a comprehensive lab-field-modeling approach

维持农业生产对粮食安全和经济发展至关重要，但也导致环境退化，这在很大程度上是由于营养元素，包括碳（C）、氮（N）、磷（P）和硫（S）从农业土壤流失到水道，在那里它们具有不利的生态影响，最重要的是藻类过度生长。最佳管理实践（BMPs）旨在创造或加强减少农田营养元素出口的条件。因此，BMPs的设计应该优化自然生态地球化学过程，在营养物质进入接收水道之前将其吸收或消除。在自然景观中，这些过程往往集中在相对较小的区域，称为“反应界面”（RI）。尽管人们普遍认识到RI对流域规模养分加工的重要性，但其系统性，基于科学的纳入农业BMPs仍然没有得到充分利用。一个关键的障碍是我们有限的理解，如何影响的RI耦合的命运和运输的C，N，P，和S在农业生态系统。因此，拟议的工作的重点将是推进农业生态系统中的RI的预测建模，使用数据合成，现场，实验室和计算方法的组合。我们将特别关注三个RI，毛细边缘，河岸区和潜流区。本项目将培养4名博士生、1名博士后研究员和12名本科生。学生将在实验室和位于安大略的土壤类型和景观梯度的四个农业现场工作。经验的理解将被编码到过程模型的个别RI和他们的水文和地球化学连接在现场和流域尺度。流程模型将为最佳管理计划的实际执行提供信息，以最大限度地发挥其效力。这项工作是重要的，因为它提供了深入了解的机制，养分保留和消除在农业生态系统中的关键RI。这将提高我们跟踪和预测景观中养分通量的能力，并提出改进的、基于证据的建议，以减少加拿大各地农业系统中的养分损失。

Sustaining agricultural production is critical to food security and economic development but also leads to environmental degradation, in large part due to the loss of nutrient elements, including carbon (C), nitrogen (N), phosphorus (P) and sulphur (S), from agricultural soils to waterways where they have adverse ecological effects, foremost excessive algal growth. Best management practices (BMPs) aim at creating or enhancing conditions that reduce the export of nutrient elements from agricultural fields. The design of BMPs should therefore optimize the natural biogeochemical processes that immobilize or eliminate nutrients before they enter the receiving waterways. In natural landscapes, these processes tend to be concentrated in relatively small zones known as 'reactive interfaces' (RIs). Despite widespread recognition of the importance of RIs for watershed-scale nutrient processing, their systematic, science-based incorporation in agricultural BMPs remains underutilized. A key barrier is our limited understanding of how RIs affect the coupled fate and transport of C, N, P, and S in agroecosystems. The focus of the proposed work will therefore be to advance the predictive modeling of RIs in agroecosystems, using a combination of data synthesis, field, laboratory, and computational approaches. We will specifically focus on three RIs, the capillary fringe, riparian areas and the hyporheic zone. Four PhD students, one post-doctoral researcher and 12 undergraduate students will be trained through this proposal. Students will work in the laboratory and at four agricultural field sites located across soil type and landscape gradients in Ontario. The empirical understanding will be encoded into process models of individual RIs and their hydrological and biogeochemical connectivity at the field and watershed scales. The process models will inform the practical implementation of BMPs to maximize their effectiveness. This work is significant as it provides insight into the mechanisms of nutrient retention and elimination at critical RIs in agroecosystems. This will advance our ability to track and predict nutrient fluxes in the landscape and make improved, evidence-based recommendations to reduce nutrient losses in agricultural systems across Canada.