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，但也会导致环境退化，这在很大程度上是由于包括碳(C)、氮(N)、磷(P)和硫(S)在内的营养元素从农业土壤流失到水道，造成不利的生态影响，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，bmp的设计应该优化自然生物地球化学过程，在营养物质进入接收水道之前将其固定或消除。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”（RIs）。尽管人们普遍认识到RIs对流域尺度养分处理的重要性，但它们在农业bmp中的系统、科学结合仍未得到充分利用。一个关键的障碍是我们对RIs如何影响农业生态系统中C、N、P和S的耦合命运和运输的理解有限。因此，拟议工作的重点将是利用数据综合、实地、实验室和计算方法的结合，推进农业生态系统中RIs的预测建模。我们将特别关注三个RIs，即毛细边缘区、河岸区和下潜带。拟培养博士研究生4名，博士后1名，本科生12名。学生们将在实验室和四个农业现场工作，这些地点位于安大略省不同的土壤类型和景观梯度。经验理解将被编码到单个RIs及其在野外和流域尺度上的水文和生物地球化学连通性的过程模型中。流程模型将为bmp的实际实施提供信息，以最大限度地提高其有效性。这项工作具有重要意义，因为它为农业生态系统中关键RIs的营养保留和消除机制提供了见解。这将提高我们跟踪和预测景观中养分流动的能力，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.