28 Jun 2024
 | 28 Jun 2024
Status: this preprint is open for discussion.

From hydraulic root architecture models to efficient macroscopic sink terms including perirhizal resistance: Quantifying accuracy and computational speed

Daniel Leitner, Andrea Schnepf, and Jan Vanderborght

Abstract. Root water uptake strongly affects soil water balance and plant development. It can be described by mechanistic models of soil-root hydraulics based on soil water content, soil and root hydraulic properties, and the dynamic development of the root architecture. Recently, novel upscaling methods have emerged, which enable the application of detailed mechanistic models on a larger scale, particularly for land surface and crop models, by using mathematical upscaling.

In this study, we explore the underlying assumptions and the mathematical fundamentals of different upscaling approaches. Our analysis rigorously investigates the errors introduced in each step during the transition from fine-scale mechanistic models, which considers the nonlinear perirhizal resistance around each root, to more macroscopic representations. Upscaling steps simplify the representation of the root architecture, the perirhizal geometry, and the soil spatial dimension and thus introduces errors compared to the full complex 3D simulations. In order to investigate the extent of these errors, we perform simulation case studies: spring barley as a representative non-row crop and maize as a representative row crop, and using three different soils.

We show that the error introduced by the upscaling steps strongly differs, depending on root architecture and soil type. Furthermore, we identify the individual steps and assumptions that lead to the most important losses in accuracy. An analysis of the trade off between model complexity and accuracy provides valuable guidance for selecting the most suitable approach for specific applications.

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Daniel Leitner, Andrea Schnepf, and Jan Vanderborght

Status: open (until 23 Aug 2024)

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Daniel Leitner, Andrea Schnepf, and Jan Vanderborght

Model code and software

CPlantBox Daniel Leitner, Andrea Schnepf, and Jan Vanderborght

Dumux-Rosi Daniel Leitner, Andrea Schnepf, and Jan Vanderborght

Daniel Leitner, Andrea Schnepf, and Jan Vanderborght


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Short summary
Root water uptake strongly affects plant development and soil water balance. We use novel upscaling methods to develop land surface and crop models from detailed mechanistic models. We examine the mathematics behind this upscaling, pinpointing where errors occur. By simulating different crops and soils, we found that the accuracy loss varies based on root architecture and soil type. Our findings offer insights into balancing model complexity and accuracy for better predictions in agriculture.