The multifaceted interface of plant roots, microbes, water, and soil can be considered a critical zone within the Critical Zone as it is host to many important dynamically linked processes, including the promotion of nutrient cycling through absorption and rhizodeposition, interaction and feedbacks with microorganisms and fungi, root‐facilitated hydraulic redistribution, and soil carbon dynamics. Such important processes in the Critical Zone have not been fully characterized and modeled in an ecohydrologic framework linking above‐ground natural and/or anthropogenic processes to below‐ground biogeochemical cycling. Specifically, the relation between root exudates and nutrient cycling remains an open challenge. Here we present the model REWT (Root Exudation in Watershed‐scale Transport) to demonstrate the systematic modeling of root exudation in an interconnected ecohydrologic framework. REWT incorporates an explicit dynamic root exudation transport model, nutrient absorption, and coupled microbial processes within the framework of a validated ecohydrologic model. Model simulations demonstrate the influence of root exudation of glucose, a polysaccharide that serves as fuel for microbes, and flavonoids, which can act as a biological nitrification inhibitor on microbial processes linked to soil carbon and nitrogen cycling. To demonstrate the capabilities of this theoretical framework, we parameterize REWT for corn and soybean crops in the Midwestern United States, and simulations indicate that rates of nitrification and respiration were substantially altered compared to model simulations in which root exudation was not explicitly included. This work demonstrates the importance of systematically incorporating root exudates into hydrobiogeochemical models and can serve to inform experimental design for active root zone processes.

中文翻译：

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模拟根系分泌物在关键区域营养动力学中的作用

植物根，微生物，水和土壤的多面性界面可以视为关键区域内的关键区域，因为它是许多重要的动态链接过程的宿主，包括通过吸收和根状沉积促进养分循环，与微生物的相互作用和反馈和真菌，促进根系的水力再分配以及土壤碳动态。在临界地带中如此重要的过程尚未在将地上自然和/或人为过程与地下生物地球化学循环联系起来的生态水文学框架中得到充分描述和建模。具体而言，根系分泌物与养分循环之间的关系仍然是一个开放的挑战。在这里，我们介绍REWT模型（分水岭尺度上的根系渗出），以证明在相互联系的生态水文框架中根系渗出的系统模型。REWT在经过验证的生态水文模型的框架内纳入了显式的动态根系分泌物运输模型，养分吸收和耦合的微生物过程。模型模拟证明了葡萄糖的根系分泌物（一种用作微生物燃料的多糖）和类黄酮（它们可作为生物硝化抑制剂）对与土壤碳和氮循环相关的微生物过程的影响。为了证明此理论框架的功能，我们对美国中西部玉米和大豆作物的REWT参数化，和模拟表明，与未明确包括根分泌物的模型模拟相比，硝化和呼吸速率发生了显着变化。这项工作证明了将根系分泌物系统地纳入水生地球化学模型的重要性，并且可以为活跃的根区过程提供实验设计依据。