Soils are key regulators of the global carbon (C) cycle. Organic amendments of soils are considered suitable to sequester C belowground and contribute to climate change mitigation. With the evolution of biomass recovery systems and the use of energy plants, agriculturally used organic amendments have diversified. The diversity of amendments with different quality (e.g. compost, digestate, biochar) challenges our ability to judge the long-term persistence of amendment C in soils prior application. Soil C persistence is predominantly an ecosystem property, but intrinsic organic matter (OM) properties still influence its persistence. Recently, a significant positive correlation between microbial short-term (i.e. 24 hours) decomposition of dissolved OM and its energetic return-on-investment (ROI) was discovered. The energetic ROI is the ratio of the total energy content to the activation energy of OM, indicating the net energy gain for microbial decomposers after an initial energy investment. It remains, however, unknown if the energetic ROI is a suitable indicator to predict the long-term persistence of organic amendments in soil. This project aims to evaluate links between the energetic ROI of organic amendments and their short- to long-term (i.e. days to year, year to decades, resp.) persistence in soils. Thereby, it will contribute to our general understanding of OM persistence in soil. Its overarching hypothesis is that soil microorganisms preferentially decompose organic amendments with a relatively high energetic ROI, leading to a longer persistence of organic amendments with a relatively low energetic ROI.

Phosphorus (P) is a fundamental element for plants. The depletion of the mineral P reserves as a chemical fertilizer will occur suddenly due to the growing world demand for agriculture. In addition, the excessive use of mineral fertilizers causes major dysfunctions of the agrosystem in the medium and long terms. This requires us to quickly discover sustainable alternatives. Large quantities of organic P and inorganic P, adsorbed to soil constituents, represent important reservoirs of P. Exploitation of these P sources, which are not readily available for crops, could be a promising avenue in agriculture. Nematodes are the most abundant animals on Earth. They are ubiquitous and play essential roles in regulating nutrient cycles in ecosystems. Within the rhizosphere, nematodes can greatly improve plant P availability from these poorly-available P sources. However, taking nematodes into account as biological beneficial actors for the increase in plant P availability has so far been largely neglected. Therefore, the mechanisms by which nematodes affect soil P fluxes and the controlling factors, both abiotic and biotic, are unknown. The O-NEMATO-P (Optimizing NEMATOde-driven P availability) project aims to explore the roles of soil nematodes in improving the availability of P for crops from poorly-available sources. The project focuses on ecological processes, mechanisms and controlling factors. We plan to explore and use nematode functional traits to relate the structure of soil nematode communities to P fluxes at the soil-plant interface, without neglecting the usual metrics of community diversity. In order to feed into the agronomic work carried out in agroecology, we are working to develop a "Pho-nem" indicator which will provide information on the capacity of an agricultural practice to intensify the ecological processes involved in the mobilization of P from sources that are not readily available for crops. To achieve this goal, advanced innovative techniques (18O labeling technique, the phytate model, multi-species co-inoculation, and bacterial strains transformed by GFP) will be used in conjunction with modeling and classification techniques by machine learning. The knowledge acquired will provide important fundamental information on the role of soil nematodes on plant P availability from poorly-available P sources. In the current framework of agronomic innovation fueled by agroecology and the ecological intensification of soil functions, our results can be used to design and evaluate the sustainability of agricultural practices by encouraging the exploitation of P sources and thus limiting the use of expensive mineral fertilizers that impact the environment.

Soil biodiversity is an important reservoir of ecosystem services and is threatened by the wide-scale use of pesticides. Evolution plays a central role in how populations persist because ecological change and evolutionary processes interact in eco-evolutionary feedbacks. These feedbacks can decrease extinction risk by allowing rapid adaptation to environmental stressors but depend on the population density and its genetic makeup. Despite evidence that soil fauna can adapt to pesticide exposure, key questions on the speed at which adaptation occurs and the costs for ecosystem functions remain unanswered. EEWORM will investigate eco-evolutionary dynamics in populations of the earthworm Aporrectodea caliginosa, a major soil engineer in agricultural systems, exposed to a pesticide mixture representative of French agricultural soils. In WP1, I will calibrate a toxicokinetic-toxicodynamic model allowing to predict the outcome of a mixture of epoxiconazole and imidacloprid - two dominant pesticides in agricultural soils - on earthworm growth, reproduction and activity and on organic carbon mineralization. In WP2, I will measure individual differences in growth reproduction and burrowing activity by following a cohort of earthworms over their lifecycle. Individuals will be split in four dose combinations ranging from low to strong effect on all traits based on the data from WP1. This will allow to adjust the TKTD model to account for individual differences in life-history traits and in sensitivity to pesticide mixture. Using lifetime reproductive success as a proxy for fitness will allow to estimate the shape and intensity of selection for all dose combinations. WP3 will test whether tolerance to pesticide exposure may also occur through transgenerational plasticity by splitting offspring from the F0 population from WP2 into exposed and control group. This WP will test different scenarios by which transgenerational plasticity may occur, either by preventing offspring from recovering from parental exposure or leading to habituation or sensitization to pesticide stress. The combined data from WP2 and 3 will therefore allow to contrast the relative influence of selection induced by pesticide exposure and transgenerational plasticity on the expression of life-history and behavioral traits. In WP4, I will use the gathered data to build an individual based model. This model will allow to predict the outcomes of pesticide exposure under field-realistic scenarios on earthworm population dynamics and derive its consequences on carbon mineralization. By combining novel experimental procedures to estimate the evolutionary impacts of pesticides on individual differences in life-history and behavior with advanced modelling approaches, EEWORM will answer a pressing environmental issue: How fast can a key soil engineer adapt to pesticide mixtures and at what cost for soil functions? This project is a unique opportunity for me to lead novel research in evolutionary ecotoxicology as a newly-recruited scientist at INRAE.

In a context of climate change, assessing the evolution of the risk associated with the contamination of wheat with mycotoxins produced by fungal species belonging to the genus Fusarium is crucial to ensure the safety of future cereal-derived food products in France. EvolTox proposes to tackle this challenge and deliver the basal knowledge and its integration in models simulating the occurrence of fusariotoxins in wheat harvests in relation to various climatic contexts. EvolTox implements a two-scale approach, combining field survey and laboratory studies to feed models. First, the representativeness of the Fusarium species/toxins over a 15-years-period will be investigated in the light of climatic and/or agronomic factors to precise the drivers that shape their distribution . Second, EvolTox proposes to associate ecophysiological and interspecies competition studies with an evolutionary biology approach to increase the accuracy and completeness of the predictive models.

The DATA4C + project is part of the open science (RDA) and soil carbon initiatives (4 per 1000 in particular). In order to meet the objectives of these initiatives, there is a great challenge to reference, in databases, not only the analyzes but also the associated metadata and to make databases interoperable. Based on this observation and the leading role played by CIRAD, INRA and IRD at national and international level on the topic of soil carbon, the DATA4C + project has the following objectives: (OS1) Define rules of good practice to describe the data in the soil carbon databases and provide them with consistent information; (OS2) Analyze the computer and legal barriers for interoperability between soil carbon databases and soil management modes in order to propose solutions for alleviating them; (OS3) Experiment with the implementation of methodological solutions formulated by the project in a French overseas department; (OS4) Exchange and disseminate internationally on the project. The results of DATA4C + are intended to be integrated into the practices and tools of CIRAD, INRA and IRD within the framework of their respective strategies relating to digital and open science. Beyond the soil carbon community, the semantics validated in the DATA4C + project will be published / disseminated and will be used by other scientific communities. In addition, solutions / options from the DATA4C + project may also be valid for other soil parameters and then support other teams. In addition, the availability of soil carbon data and metadata will eventually have very different targets: States, engineering offices ...