Vegetation optimizes its geochemical environment for resource management via root exudation. We refer to the soil zone where biogeochemical behavior is significantly influenced, directly or indirectly, by root processes as the vegetation induced reactive zone (VIRZ). Root exudates react with VIRZ soil substrates creating temporally variable chemical environments through depth that extend below the rooting zone, impacting weathering, and releasing solutes and gases. We present a new framework, REWTCrunch, to capture VIRZ dynamics by integrating three modeling advances: the multicomponent reactive transport model CrunchFlow, the root exudation model REWT, and the multilayer canopy‐root ecohydrologic model MLCan. REWTCrunch's high‐resolution, process‐based simulation of root exudation, and the transport and transformation of carbon (C) and nutrients according to mass‐balanced and charge‐balanced reaction networks gives new insight into vertically resolved root‐soil‐microbe‐water interactions and their influence on solute fluxes at a daily timescale. We benchmark REWT and CrunchFlow, illustrate coupling mechanisms, and present REWTCrunch simulations for an agricultural site in the US Midwest. Results demonstrate root‐sourced reactive C can augment or reduce solute concentrations in the soil by several orders of magnitude. Silicate weathering products illustrate after‐harvest effects of plant C inputs in leaching patterns. Calcium simulations reveal the development of a stable weathering front. Aluminum concentrations are particularly responsive to root‐sourced reactivity, and analysis of leaching concentration versus leaching flux indicates hysteresis behavior. REWTCrunch significant improves our ability to simulate the link between root processes and soil biogeochemistry, thereby filling an important gap in the numerical simulation of root processes, weathering, and long‐term soil health.
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.
more » « less- NSF-PAR ID:
- 10449591
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Water Resources Research
- Volume:
- 56
- Issue:
- 8
- ISSN:
- 0043-1397
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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REWTCrunch: A Modeling Framework for Vegetation Induced Reactive Zone Processes in the Critical Zonemore » « less
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