[Thesis defence] 20/12/2024 - Cécile SERBOURCE: "Study of the bioturbatory activity and life history traits of enchytreids (Annelida, Oligochaeta) in Mediterranean agricultural soils". (UMR EMMAH)
Cécile SERBOURCE will submit her thesis on 20 December 2024 on the theme: "Study of the bioturbatory activity and life history traits of enchytenids (Annelida, Oligochaeta) in Mediterranean agricultural soils".
Date and place
Oral defense scheduled on Friday 20 December 2024 at 8.30 a.m.
Venue: Pôle Agrosciences, 546 Rue Baruch de Spinoza, 84140 Avignon, France
Room: Amphitheatre AGROSCIENCES
Discipline
Agricultural sciences
Laboratory
UMR 1114 EMMAH - Mediterranean Environment and Modelling of Agrohydrosystems
Composition of the jury
Ms Céline PELOSI | INRAE | Thesis supervisor |
Mr Stéphane SAMMARTINO | Avignon University | Thesis co-supervisor |
Ms Isabelle COUSIN | INRAE | Examiner |
Mr Bart MUYS | University of Leuven (KU Leuven) | Examiner |
Mr Stephan HATTENSCHWILER | CNRS Montpellier | Rapporteur |
Mr Yves COQUET | AgroParisTech | Rapporteur |
Summary
Cultivated soils are under the dual influence of farming practices and climate change. Conventional practices (use of chemical inputs, ploughing) have compromised soil health and its ability to provide essential ecosystem services. As part of the agro-ecological transition, 'soil engineer' organisms such as earthworms and enchytreids can be used as a lever to support soil health and offer opportunities to strengthen the resilience of ecosystems in the face of climate change. This thesis explores the action of enchytreids in the soil and provides information on their interactions with biotic and abiotic factors in the environment by answering several specific questions: (1) Do enchytreids show a different sensitivity to environmental stress factors than earthworms? (2) What is the impact of their bioturbation activity on soil porosity? (3) Is it possible to determine a soil desiccation threshold at which their life cycle and behaviour are affected? (4) How can the impact of enchytreids on soil hydrodynamic properties be quantified? The first chapter puts the thesis work into context by presenting the current state of the art on enchytreids and the lines of research explored.
In the second chapter, a quantitative literature review (meta-analysis) is used to compare the sensitivity of earthworms and enchytheids to various environmental stress factors. These two groups have similar functional roles but at different spatial scales in soils. Their sensitivity to environmental factors influences biological processes and, consequently, soil functioning. This analysis reveals that these two groups of organisms have comparable sensitivities, whatever the species or type of stress. The third chapter presents the response of the model species of enchytraeid Enchytraeus albidus to water stress. Under optimum moisture conditions (>20 % soil mass water content), survival, feeding and reproduction are maximised. From 16 %, feeding decreases, and from 12 %, severe deleterious effects appear, particularly on survival and reproduction, as well as on the water content of the animals. The fourth chapter is divided into two sections. Section 1 is devoted to a study of the impact of the bioturbation activities of two enchytraid species, Enchytraeus albidus and Enchytraeus crypticus, on soil porosity using images acquired by X-ray microtomography.
In this experiment, enchytreides had a moderate effect on total pore volume, but their presence and activity increased the connectivity of the pore network. In addition, the pore size distribution was homogenised around the diameter of the animals studied (250-550 µm). These changes in the characteristics of the pore space are likely to influence the flow and retention of water in soils. The second section of this chapter presents a protocol for studying the impact of enchytreid bioturbation activity on soil hydrological properties. This chapter includes a detailed experimental design, using soil columns and rainfall simulations with the injection of isotopic tracers. Results from control columns without enchytreides are presented and used to discuss the limitations of the protocol and approach. This thesis contributes to a better understanding of the role of enchytreids as bioindicators and soil engineers. Encytheids are proving to be significant bioindicators, playing an essential role in the agroecological transition by providing essential information on changes in soil management and supporting sustainable agricultural practices.
Keywords Agroecology, Enchytreides, Bioturbation, X-ray microtomography, Climatic stress, Water infiltration
Mis à jour le 9 December 2024