A process-based modeling of soil organic matter physical properties for land surface models-Part 2 - Global land surface simulations and mineral soil compaction adjustment

Sep 15, 2026

A process-based modeling framework represents how soil organic matter affects soil physical properties in land surface models and is evaluated in global simulations using the ISBA-CTRIP system. Volumetric organic matter fraction and phase-specific densities are derived from soil organic carbon and bulk density, while hydraulic and thermal parameters follow model-consistent mixing rules. An optional mineral soil compaction adjustment is tested under contrasting assumptions for texture-calibrated pedotransfer functions versus gridded bulk density products, using multidecadal offline experiments and site-to-global benchmarks.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages54

Reading Time2 h 16 min

AccessFree to download

Abstract

Introduction

Land surface models and the role of soil physical properties

Soil organic matter impacts on hydraulic and thermal behavior

Volume-based links between organic/mineral constituents and soil properties

[https://doi.org/10.5194/egusphere-2026-860](https://doi.org/10.5194/egusphere-2026-860) Preprint. Discussion started: 6 March 2026 􀀍c Author(s) 2026 . CC BY 4.0 License. A process-based modeling of soil organic matter physical properties for land surface models-Part 2 : Global land surface simulationsand mineral soil compaction adjustment Bertrand Decharme 1 , Diane Tzanos 1 , Lucas Hardouin 1 , Aaron Boone 1 , Marie Minvielle 1 , Patrick Le Moigne 1 , and Rémi Gaillard 2 1Météo-France, CNRS, Univ. Toulouse, CNRM, Toulouse, France. 2Faculty of Environment, Science and Economy, University of Exeter, Exeter, UK Correspondence: Bertrand Decharme ([bertrand.decharme@meteo.fr](bertrand.decharme@meteo.fr)) Abstract. In the companion paper, Decharme (2025) developed a process-based framework using soil mixture theory to represent the effects of soil organic matter on soil physical properties in land surface models. The present study extends this work by testing the framework in global land surface simulations with the ISBA-CTRIP land surface modeling system. The approach derives the volumetric organic matter fraction and phase-specific densities from soil organic carbon and bulk den- 5 sity using mass volume relationships, and computes hydraulic and thermal parameters using mixing rules consistent with the model physics. We also introduce an optional mineral soil compaction adjustment, under the assumption that texture-based pedotransfer functions are calibrated on weakly compacted samples, whereas gridded bulk density products mostly reflect in situ conditions that include varying degrees of compaction. We examine the effects of both developments in multidecadal global offline simulations forced by a standard meteorological dataset and driven by SoilGrids soil inputs. Four configurations are 10 compared, a mineral-only control, a previous empirical scheme, the new process-based scheme, and its compaction-adjusted variant. The evaluation combines site-scale constraints on porosity and hydraulic behavior with large-scale benchmarks of the terrestrial water and energy cycles, including terrestrial water storage variations, river discharge, evapotranspiration, soil temperature, and active layer thickness. Overall, the global experiments suggest that the new process-based scheme produces more consistent large-scale hydrothermal responses than the previous empirical scheme, whereas the compaction adjustment plays 15 a secondary role and mainly acts as a local modulator. 1 Introduction All physical and chemical exchanges of water, energy, carbon, and momentum between the terrestrial surface and the atmosphere in Earth system models are computed by land surface models (LSMs) . These models provide lower boundary conditions for weather and climate simulations and are key components of coupled modeling systems. LSMs resolve processes such as pre- 20 cipitation interception and infiltration, evapotranspiration, runoff generation, snow accumulation and melt, soil heat diffusion, vegetation phenology, photosynthesis, autotrophic and heterotrophic respiration, soil carbon dynamics, etc. Their accuracy directly influences the simulation of land–atmosphere fluxes and the representation of surface climate, hydrology, and biogeo- [https://doi.org/10.5194/egusphere-2026-860](https://doi.org/10.5194/egusphere-2026-860) Preprint. Discussion started: 6 March 2026 􀀍c Author(s) 2026 . CC BY 4.0 License. chemical cycles across spatial and temporal scales (Bonan and Doney, 2018 ; Blyth et al., 2021) . Accurate representation of soil physical properties in LSMs is essential for correctly simulating the partitioning of water and energy at the land surface. Soil 25 porosity and hydraulic conductivity determine infiltration, runoff and drainage, thermal conductivity and heat capacity affect soil temperature profiles, and water retention properties regulate the availability of moisture to plants and microbial processes. These vari

FAQs

What does the study extend compared with the companion paper?

It tests the process-based soil organic matter framework in global land surface simulations with ISBA-CTRIP and adds evaluation of hydraulic/thermal parameter computations and an optional compaction adjustment.

How are volumetric organic matter fraction and phase-specific densities obtained?

They are derived from soil organic carbon and bulk density using mass-volume relationships, consistent with the model physics.

What is the purpose of the mineral soil compaction adjustment?

It modulates mineral soil effects by addressing differences between texture-based pedotransfer calibrations on weakly compacted samples and gridded bulk density products that reflect in situ compaction variability.

Sep 15, 2026

Uploaded by Lucas Vance