HDR Katell Quénéa

Titre : Devenir de la matière organique des sols : influence des différents processus de stabilisation

Devant un jury composé de :

Mme Isabelle Basile-Doelsch, DR INRA, UMR 7330 CEREGE, Aix-en-Provence, rapporteur
Mme Tiphaine Chevallier, CR HDR IRD, UMR Eco&Sols, Montpellier,rapporteur
M. Abad Chabbi, DR INRA, Ecosys, Grignon, rapporteur
M. François Baudin, Professeur des universités, UMR 7193 ISTEP, Sorbonne Université, Paris, examinateur
M. Luc Abbadie, Professeur des universités, UMR 7618 IEES, Sorbonne Université, Paris, examinateur
Mme Camille Dumat, Professeur des universités,UMR EcoLab, Toulouse, examinatrice
Mme Sylvie Derenne, DR CNRS-EPHE, UMR 7619 METIS, Sorbonne Université, Paris, invitée

Abstract : Soil organic matter (SOM) is a key compartment of the biosphere. SOM constitutes an important pool of carbon (twice the atmospheric carbon pool), and is highly influence by anthropic activities. In addition, SOM is one of the main drivers allowing the achievement of ecosystem services in soils, and is necessary to maintain these services. In consequence understanding the fate of soil organic matter is crucial. SOM matter stock is a balance between the input of SOM (plants, microorganisms, fauna, organic residues) and its mineralization by soil organisms. However, many factors influence the rate of SOM mineralization.

During my researches, I have investigated the role of the SOM chemical composition and of organo-mineral interactions on the residence time of SOM. I first have evaluated the role of chemical composition by characterizing a fraction of SOM isolated chemically, and supposed to be recalcitrant to biodegradation; then its persistence in soil was measured. Thereafter, I have studied the influence of earthworm in SOM fate, as their casts present important organo-mineral interactions. The aim was to evaluate the incorporation of fresh organic matter by earthworm in soil, and the consecutive influence on it dynamic to finally estimate a SOM stabilization potential by those structures. Another aspect of my research focused on the influence of industrial activities leading to pollution in trace element on soil. Attention was specially drawn on the influence of trace element contamination on SOM degradation.

In my forthcoming projects, I would like to deepen the knowledge on drivers of SOM dynamic in soils. My next project will aim at evaluating the evolution of the dynamic of SOM specifically included in earthworm casts with time. The effect of different SOM concentration and the chemical nature of the OM include in soil will also be assess in mesocosms. This project will be carried out in collaboration with microbiologists to have a simultaneous insight into microbe communities’ evolution and activities with time. Thereafter, the results obtained could be extended to soils with different mineralogy, and submit to perturbation such drying-wetting cycle. In another project I would like to follow the degradation of plants contaminated in TE to evaluate the impact of the TE on SOM degradation when the plant residues would be incorporated in soil.