Scientific themes

Theme 1 focuses more specifically on the ‘soil - unsaturated zone - saturated zone’, with the aim of better understanding and imaging the complex and heterogeneous nature of this environment. The scales involved range from the pore space (more or less impacted by biological activity) to the larger scales involved in global flows and aquifer recharge. More specifically, we seek to ‘Identify, Characterise and Model’ complex environments using non-invasive methods for areas that are inaccessible to direct measurement. The EMMAH UMR is particularly interested in the physical properties (electromagnetic, mechanical) used to describe the solid structure and water content of media at various scales of interest. Our research focuses on three main scientific challenges:

• Exploring new approaches by combining different physics (electromagnetism, mechanics) to gain in accuracy and reliability (time of flight, surface waves, mean free path, FWI) in the reconstruction of maps of media properties.
• Developing and improving measurements using existing non-invasive geophysical equipment (GPR, ERT, high-resolution seismic) or equipment under development (optical interferometry, low-cost hectometric loop). These approaches can be transposed to different scales, from the laboratory to the geological massif.
• Extending and optimising inversion methods, in particular by coupling electromagnetic inversion and mechanical inversion to integrate more information through the use of elaborate petrophysical relationships.

The context of agro-ecological transition requires us to consider plant cover of increasing complexity, while the study of territories requires us to take into account a large number of species and varieties in order to cover all agricultural plots exhaustively. There is therefore a need for plant cover characterisation methods that can be implemented in a wide range of cases and environmental conditions, for field crops, perennial crops and complex cover crops (e.g. agroforestry, crop associations). This involves characterising the morphological, biochemical, phenological and functional traits of cultivated plants. The characterisation of these traits, which can be described in the broad sense of phenotyping, can be integrated into numerous applications such as varietal selection or modelling of land use. Traditional characterisation methods are costly in terms of manual measurements. It is therefore important to develop automated, non-destructive, high-throughput methods. These can be based on observations using satellite remote sensing on a large scale and proxidetection (observations made close to the targets to be characterised, using sensors mounted on a connected stake or a drone, for example) on a smaller scale.

Our research focuses on three scientific challenges

• Developing robust phenotyping methods to gain access to more morphological (aerial and root), biochemical or phenological traits in field crops and more complex cover crops.
• Develop functional phenotyping approaches. This involves determining, for a species or variety of plant, the key parameters of ecophysiological functions integrated into crop function models. These parameters describe, for example, the sensitivity of biomass production to temperature or water stress.
• Exploit the synergies between different proxi and remote sensing tools (complementary sensors, spatial and temporal resolutions) to gain a better understanding of plant-environment interactions.

Soil quality can be defined as its capacity to provide ecosystem services. These are strongly influenced by the biological activity of the soil, which modifies its transfer properties, its retention capacity and the uptake of water and nutrients by plants. In the context of global change, and climate change in particular, there is a strong need to maintain and even restore soil quality. In this field of research, the EMMAH joint research unit is focusing on describing, understanding and modelling the relationships between living organisms (roots/rhizosphere, invertebrates, microbial communities) and mass transfer processes in the soil. One of the applied objectives is to design, propose and evaluate, using indicators (soil infiltrability, retention capacity, root uptake capacity, etc.), agro-ecological practices that can be used as part of ecological engineering initiatives and nature-based solutions to promote soil and water quality by encouraging biodiversity.

The EMMAH UMR’s work focuses on the following scientific challenges:

• Characterising the soil and its changes, with the definition of relevant indicators for studying the dynamics of physical changes in the soil and the processes that take place in it (water flow/retention), under the action of living organisms and roots subject to climate change and practices (e.g. inputs of organic matter, reduction in phytosanitary treatments, cover crops) as part of the agroecological transition.
• To take account of pore space in models of water transfer and retention in soils at different scales (from the pore (µm) to the homogeneous entity in the landscape (km²)) by studying in particular the partition between preferential flows and diffusive transfers.
• Integrating the dynamics of porosity induced by biological activity into transfer models.

The agricultural plot and the territory are important levels of organisation for tackling the problem of global change, since they represent relevant levels of intervention for implementing adaptation measures. A representation of agricultural production in relation to environmental constraints, such as water resources, soil, climate and farming practices, should make it possible to support the necessary consultation between local stakeholders, who may have sometimes divergent interests. In this way, the models developed by the EMMAH UMR can be used to analyse future scenarios, develop sustainable agricultural management options for adapting to global change or be incorporated into decision-making tools. In addition, measures to adapt to global change will incorporate agro-ecological practices that need to be represented in the models. The scale of the territory calls into question research on subjects such as the representation of the diversity of situations (agricultural practices, environmental conditions), and this with information that is often limited to exhaustively characterise all the spatial entities to be considered. Understanding the determinism and scenarios of territorial change should make it easier to support and monitor adaptation measures and their impact on resource management and plant production.

The EMMAH UMR's work focuses on the following scientific challenges:

• Characterising crops, resources (water and soil), climate and farming practices (particularly irrigation) throughout the region, using various sources of spatialised information such as remote sensing, environmental databases (soil, climate, topography) and administrative databases.
• Modelling the water requirements and water stress of crops (particularly perennial crops) across the whole of France, with a focus on developing crop models for perennial plants (particularly orchards). These models will have to take into account of agro-ecological practices (combined crops, biodiversity management, organic fertilisation management, etc.), stress/production relationships and represent water flows at the soil base in order to understand aquifer recharge.
• Developing strategies for adapting to global change on several scales (plot, territory) to cope with the pressures on water. In particular, work will be carried out on crop selection and practices to ensure efficient and shared use of irrigation water resources on a regional scale.
• Estimating the impact of cropping systems on groundwater recharge mechanisms.

Theme 5 focuses on water dynamics in underground hydrosystems and their interactions with surface flows. As the world's largest freshwater reserve, groundwater plays a central role in maintaining ecosystems and helping mankind adapt to global change. The strategic importance of groundwater for water supply is intensifying as climate extremes (droughts and floods) increase rainfall variability and surface runoff while limiting water infiltration into aquifers. The increasing pressure on groundwater resources is a major scientific, environmental and societal challenge, but innovative solutions for the sustainable management of these vital reserves will not be possible without an improved understanding of the structure and functioning of underground hydrosystems and their recharge mechanisms.

The scientific challenges that structure the theme are:

• How can we improve the characterisation and understanding of recharge processes in underground hydrosystems? Soil and associated ecosystems play a key role in the partitioning of water flows between runoff, recharge and evapotranspiration. We are seeking to understand how the properties of ecosystems, their management and changes in rainfall patterns influence this partitioning. From a methodological point of view, our developments are based on in situ instrumental development, tracing (isotopic and geochemical), geophysics and remote sensing.
• What is the internal functioning of underground hydrosystems? This requires first of all characterising and modelling the geological structure of aquifers and then assessing their operating properties: spatio-temporal distributions of water stocks (inert - active), water-rock interactions, changes in the matrix, changes in hydrodynamic parameters, and distribution of water residence times.
• Modelling underground hydrosystems: To synthesise the data and produce simulation tools, we are developing hydrodynamic models that take into account the specific characteristics of the different types of aquifer (porous, fractured, karstified) and interactions with surface flows. The parameterisation and evaluation of these models is an important part of our work, with the aim of better constraining the system through knowledge of boundary conditions (recharge, groundwater-river exchanges) or tracing.