Toward a mechanistic understanding of coupled biogeochemical cycles in human-dominated landscapes

人类活动正在深刻地改变地球化学循环，对提供对社会至关重要的生态系统服务产生重要影响。农业中的可持续养分管理战略是减少这些影响的关键杠杆，同时支持长期粮食安全和水质。然而，我们对农业活动和城市化如何影响生物地球化学循环（如氮，磷和碳）之间的相互作用，从而影响生态系统服务的了解相对有限。另一个管理挑战是，我们缺乏机制模型，这些人类对养分循环的影响如何调节特定服务的提供。随着全球粮食需求的增加和城市化的继续，缩小这些与人类主导的系统有关的知识差距至关重要。我的研究计划将解决这些挑战，同时培训学生在统计和空间分析，养分收支核算，生态系统服务modeling.A的第一个目标，我和我的学生是量化土壤氮，磷，有机碳的比例在不同的农业生态系统通过从全球已发表的研究数据的合成。我们将使用这些数据来测试气候，土壤类型和农场管理在多大程度上介导土壤养分比例。其次，我们将探讨具体的养分管理策略如何影响土壤养分平衡和提供多种生态系统服务的假设驱动的机制模型。我们的主要重点将是农业养分使用和水质之间的关系，包括氮磷使用比例的变化如何影响北美下游湖泊和河流的水质。以城市地区为重点的第三个目标是量化从农业用地流向城市的养分和碳流量的大小和变化。我们的模型将能够估计城市饮食中包含了多少肥料使用，以及这如何影响当地农田根据其养分比率从城市废物流中回收养分的能力。这些相互关联的目标将提供新的理解，即养分和碳的流动如何紧密地联系在人类主导的景观内部和之间，以及农业养分管理如何成为一种机制，推动在空间和时间上提供多种生态系统服务的变化。我的研究计划的总体目标是帮助告知我们如何能够平衡竞争目标，以提高农业生产力和环境质量在农业集约化和城市化的时代。我提出的研究结果将有助于推进农业和城市层面的耦合地球化学循环的跨学科研究，在加拿大和国外的土地管理者和市政府的潜在应用。

Human activity is profoundly altering biogeochemical cycles, with important implications for the provision of ecosystem services that are vital to society. Sustainable nutrient management strategies in agriculture are a critical lever to reduce these impacts while supporting long-term food security and water quality. Yet, we have relatively limited understanding of how agricultural activities and urbanization affect the interaction among biogeochemical cycles (such as nitrogen, phosphorus, and carbon) that can in turn influence ecosystem services. Another management challenge is that we lack mechanistic models of how these human impacts on nutrient cycling moderate the provision of specific services. Closing these knowledge gaps related to human-dominated systems is critical as global food demand increases and urbanization continues. My research program will address these challenges while training students in statistical and spatial analysis, nutrient budget accounting, and ecosystem service modeling.A first objective for my students and I is to quantify the ratio of soil nitrogen, phosphorus, and organic carbon in diverse agroecosystems through synthesis of data from published studies worldwide. We will use these data to test to what degree climate, soil type, and farm management mediate soil nutrient ratios. Second, we will explore how specific nutrient management strategies affect soil nutrient balances and the provision of multiple ecosystem services using hypothesis-driven mechanistic models. Our primary focus will be on the relationship between agricultural nutrient use and water quality, including how shifts in the ratio of nitrogen versus phosphorus use affects water quality in downstream lakes and rivers across North America. A third objective focussed on urban areas is to quantify the magnitude and variation of nutrient and carbon flows from agricultural lands to cities. Our models will enable estimation of how much fertilizer use is embodied in urban diets and how this affects the capacity of local croplands to recycle nutrients from urban waste streams based on their nutrient ratios.These interrelated objectives will provide new understanding of how tightly flows of nutrients and carbon are linked within and across human-dominated landscapes, as well as how agricultural nutrient management could be a mechanism that drives changes in the provision of multiple ecosystem services over space and time. The overall goal of my research program is to help inform how we can balance competing aims to enhance agricultural productivity and environmental quality in an era of agricultural intensification and urbanization. Findings from my proposed studies will contribute to advancing interdisciplinary research on agricultural and urban dimensions of coupled biogeochemical cycles, with potential application for land managers and city governments in Canada and abroad.