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Theme 1: PLASTISOL - Fate of microplastics in soils - what indicators of sources, levels and impacts for soil quality and health?

The overall objective of the Plastisol project is to develop indicators of the presence of microplastics (MP) in soils by considering both their origin and the transformations of PM upstream but also their impacts on soil life. To develop relevant detection methods, PM will be monitored from in organic wastes treatment processes to their application into soils, where their impacts on plants, living organisms and microorganisms involved in functions essential for soil quality and health will be evaluated.

For the team Dive-N, the objective is to define microbial and plant indicators to assess (i) the biodegradability of PM in the soil, (ii) the impact of PM on maintaining soil fertility, (iii) the impact of MP on plant productivity, but also (iv) the environmental consequences on the ecosystem.  To achieve this goal, we will assay the impact of the size of MP and the presence of organic matter on the activity and abundance of microbial communities involved in C mineralization and in N cycle, especially nitrifying and denitrifying communities, in planted and non-planted soil.

• ADEME, Project leader M.F Dignac iEES (Paris), WP leader: A. Richaume
• Labs involved : iEEs (Paris), LBE (Narbonne), Ecosys (versailles), ChroEnvironnement (Besançon)

Theme 2: MINDSET - Role of soil MIcrobial communities involved in N cycling for the Delivery of ecosystem SErvices provided by forest Tree species

Biological inhibition of nitrification (BNI) is a plant ecological strategy evolved especially in ecosystems with low soil N availability, including forest ecosystems, to minimize N losses and effectively utilize the scarce N resource. BNI corresponds to the release of specific compounds to the soil via decomposition of plant litter or root exudation. By limiting nitrification, it facilitates soil N build-up and promotes a more closed N cycling, likely with positive consequences for N-related provisioning, supporting and regulating services.

MINDSET proposes to:

• assess the role of functional microbial groups of the N cycle, i.e. their (specific) activity, abundance and diversity, in the provision of four different ES provided by forest plots dominated by BNI or non BNI tree species, i.e. wood production, water purification, soil fertility maintenance and climate regulation,
• quantify the synergies or trade-offs that exist between ES using proxies for these services.

EC2CO MICROBIOME, Project leader A. Florio

Platforms involved: AME, PGE

Theme 2: StratéCoCyN - Control strategy developed by Japanese Knotweed on the N cycle microorganisms.

Biotic interactions of a non-trophic nature play an important role in the functioning of ecosystems. Recent literature demonstrates that close non-trophic interactions between plants and N cycle microorganisms exist and that some plant species have developed strategies leading to improved N acquisition, based on the control of N microbial activities. In the case of invasive species, these controls could be complex and very effective. In this context and using the invasive plant model of the Fallopia spp., the StratéCoCyN project proposes an integrative approach of this N cycle control through two complementary studies, based on the following question:

The control of microbial N activities by Fallopia spp., leading to an efficient and adapted mineral nitrogen acquisition strategy, is it modulated by soil abiotic and biotic conditions, and/or the plant developmental state, and/or the season?

A first study in microcosms and a second in situ will be developed during this project and will assess the control strategy developed by Fallopia spp. on the nitrogen cycle and associated microorganisms and to decipher more precisely the conditions driving this control.

• EC2CO HYBIGE, Project leader: Florence Piola (LEHNA) & Amélie Cantarel)
• Platform involved: AME, PGE, CESN
• PhD Student/Post-doc: Cédric Béraud (2021-2024, PhD student).

Theme 3: IMMINENT - IMproving Microbial INoculation based on Ecological Niche Theory – From theory to practice

IMMINENT, which overall structure is presented below,  aims at developing strategies to improve the performance of biostimulants by understanding how they interact with the soil native communities and guiding inoculation practice accordingly. The project will lead to major breakthroughs, i.e.: (1) the development and evaluation of more efficient inoculation strategies based on ecological niche theory – through the use of repeated inoculations, making the use of biostimulants more robust; and (2) the development of new inoculants and inoculation strategies aiming at N₂O mitigation.

• ANR, Project leader X. Le Roux
• PhD Student/Post-doc: Théo Valette (2021-2024, PhD student)
• Labs and Societies involved: AgroEcology (Dijon), IPREM (Pau), Univ. Groningen (Netherlands), Euralis Céréales, Biovitis SA.