Section 1: Thermo-Hydraulic (TH) Processes within the Soil-Vegetation-Atmosphere (SVA) Interaction


• Subsection 1a: Experimental Thermo-Hydro laboratory characterisation of rooted soils

Subsection 1a will report experimental research on the thermo-hydro (TH) properties of rooted soils, focusing on the soil-root system, which constitutes the subsurface component of the environmental compartment (SVA continuum). This subsection will include studies exploring the multi-physical processes that govern soil matrix–root interactions, with special focus to the measurement of thermal and hydraulic parameters characterising the constitutive laws controlling seepage, phase transitions, evaporation, transpiration, and, on the whole, the water balance. Biological processes will also be considered, including root development and plant biological activity, both of which influence the evolving properties of the composite material—the rooted soil. To this aim, contributions will present datasets characterising the TH properties of rooted soils, as well as monitoring data capturing the temporal evolution of the involved processes. These data may derive from laboratory experiments, physical modelling, or field investigations.


• Subsection 1b: Site-scale hydrological processes within the SVA system – insights in the Runoff and Leaf Interception

This subsection will specifically address the hydrological aspects of relevance within the SVA interaction, with particular emphasis on the characterisation, investigation, and monitoring of runoff and leaf interception processes at the site scale. This session will bring together contributions from specialised experts, including hydrologists and related specialists, aimed at deepening the understanding of how vegetation influences surface water dynamics through interception and its subsequent effect on runoff generation and distribution. The discussion will cover both methodological approaches and case studies, highlighting advances in field monitoring techniques, data interpretation and modelling.


• Subsection 1c: Monitoring of evaporation and transpiration fluxes within the SVA interaction

Subsection 1c will focus on the monitoring of evaporation and transpiration water fluxes within the SVA interaction, both at the site scale and in physical models, with the aim of generating reference datasets for comparison with numerical predictions. These predictions will integrate the constitutive laws and parameters defined in Subsection 1a, supporting the validation and refinement of coupled thermo-hydro models. The activity will involve experts specialised in this scientific field, including soil scientists, agronomists, and other relevant professionals.


• Subsection 1d: Coupled numerical Thermo-Hydraulic modelling of SVA interaction

This subsection will be entirely devoted to the numerical modelling of Soil-Vegetation-Atmosphere (SVA) interactions. The modelling efforts will focus on reproducing and interpreting the complex exchange processes of water and energy occurring within the soil-root system and between the soil and the atmosphere. Particular attention will also be given to the development of new numerical schemes and modelling approaches, designed to address the most relevant processes identified through the activities outlined in Subsections 1a, 1b, and 1c. Also, the numerical simulations will integrate the experimental insights, constitutive laws, and parameter values derived and validated in these subsections, ensuring consistency between observed and modelled behaviour. The numerical modelling reported in this section should address not only thermo-hydraulic processes but also the broader thermo-hydro-mechanical (THM) coupling, including also processes such as the role of the vegetation-induced suction / soil-root composite water content, on the overall behaviour. The more traditional “ground reinforcement” role of roots will be specifically addressed in Section 2. The aim is not only to develop reliable predictive models capable of representing coupled thermo-hydro-biological processes across a range of spatial and temporal scales — supporting both scientific research and practical applications, such as risk assessment, ecosystem management, and climate adaptation strategies — but also to consolidate and synthesise the knowledge produced throughout the previous phases of the research.

Section 2: Mechanical Characterisation of Rooted Soils


• Subsection 2a: Experimental laboratory characterisation of the multiscale Hydro-Chemo-Mechanical behaviour of rooted soils

This subsection will address the experimental investigation of the hydro-chemo-mechanical behaviour of rooted soils at the laboratory scale. This includes the identification and quantification of key physical and mechanical properties such as soil strength, stiffness, permeability, influenced by roots’ type, species and architecture, and chemical interactions. The research aims to define and validate constitutive models capable of accurately describing the coupled hydro-chemo-mechanical response of the root-soil composite material. A multiscale perspective should be adopted, linking the interaction between soil particles/grains  and root structures at the microstructure level, and the observed soil behaviour at the scale of the soil volume element,  to ensure reliable interpretation and upscaling of laboratory findings to field-scale applications, eventually.


● Subsection 2b: Field scale characterisation of the Hydro-Chemo-Mechanical behaviour of rooted soils

In this subsection, field-based experimental investigations aimed at assessing the mechanical properties of rooted soils under natural conditions will be addressed. In particular, the in-situ measurement of rooted soil strength and stiffness, and root-soil interaction mechanisms, accounting for the spatial variability introduced by root distribution, soil layering, and other environmental factors. The objective is to capture the mechanical response of rooted soil masses at the site scale, providing essential data to validate and calibrate constitutive models and to support the design of nature-based solutions for slope stability, erosion control, and soil reinforcement.


● Subsection 2c: Numerical modelling of the behaviour of rooted soils and slopes under static and dynamic loading conditions

This final subsection deals with the conceptual and numerical modelling of the mechanical behaviour and stability of rooted soil or slopes, potentially subjected to both static and dynamic (seismic) loading conditions. The aim of this subsection is to report advances in the understanding of how root systems influence slope deformation, failure mechanisms, and energy dissipation during seismic events, together with the corresponding numerical modelling. The modelling activities include the development and calibration of advanced soil-root interaction models, with particular emphasis on accurately representing the root-soil interface behaviour upon monotonic and cyclic loading. The final aim is to integrate root reinforcement effects into predictive models for slope stability assessments, combining laboratory data (subsection 2a), field observations (subsection 2b), and computational simulations to improve the reliability of both static and seismic design approaches.

Section 3: RootS25 Group Identity and Research Challenges


The third section, scheduled for the closing part of the second day, will focus on defining the research identity of the group and outlining the scientific challenges that call for collaborative efforts. The discussion will aim to:

● Synthesize knowledge across the sub-compartments — rooted soil, vegetation, and atmosphere.
●   Promote an integrated understanding of the Soil-Vegetation-Atmosphere (SVA) continuum as a dynamic environmental system and its behaviour over time.
●   Outline a conceptual framework designed to:
i) identify the most urgent research gaps, guiding future scientific directions;
ii) explore opportunities for new collaborations among the various research groups participating in RootS25, each contributing with cutting-edge expertise in specific fields;
iii) allow for the identification of additional issues or gaps, receiving those raised by the audience (scientists, practitioners, stakeholders, etc.);
iv) support the final selection of research priorities, which will define both the future agenda of the RootS group and the foundational pillars of the shared conceptual framework.