Pelosi, Céline (2008) Modelling Lumbricus terrestris population dynamics in agricultural fields. Contribution to the study of cropping system impacts on earthworm communities. PhD thesis Agronomie, Ecologie, AgroParistech 2008AGPT0057 p.95.

Full text available as: - Thèse_C._PELOSI.pdf ( 3152 Kb )

Licence: Copyright

Abstract

Earthworms, which represent a major component of soil macrofauna, are often

presented as biodiversity and soil quality indicators. Moreover, they are deemed to be

ecosystem engineers since they directly or indirectly impact the availability of resources to

other species as plants and microorganisms. Earthworms play a central role in the ecological

functioning of agroecosystems thanks to their contribution to processes influencing physical,

chemical and biological soil components.

This work is aimed at understanding and modelling earthworm population

dynamics in cultivated fields and to study the impact of cropping systems on earthworm

communities. Our model, WORMDYN, is a stochastic stage-based Lefkovitch matrix model

which accounts for vertical migrations and predicts Lumbricus terrestris dynamics in

ploughed and superficially tilled plots (Grignon, France). In the model, the earthworm

population is divided into four developmental stages (cocoons, juveniles, sub-adults, and

adults) and life cycle parameters depend on soil temperature and water content which are the

main factors influencing L. terrestris short-term dynamics. The model parameters were

estimated from the available literature.

This study of L. terrestris population dynamics entailed many samplings in cultivated

fields. However, various methods are classically used for earthworm samplings. We thus

wanted to determine the most suitable earthworm sampling method, combining efficiency

and manipulator safety. The first part of this work thus presents the comparison of three

chemical expellants for earthworm sampling.

Then, WORMDYN structure is presented, as well as the comparison between model

outputs and experimental data. A sensitivity analysis was carried out to identify the

parameters which should be estimated with a higher precision in order to improve the

predictive capabilities of the model.

Finally, to assess the impact of cropping systems on earthworm communities, data

were collected in a long-term trial including three cropping systems: a conventional system, a

“Direct seeding living Mulch-based Cropping system” and an organic system without

fertilisation. Results were used to study WORMDYN behaviour in these situations and to

get information to improve model performance.

Table of content

Chapitre 1 - Introduction générale et problématique __________________ 1

1. Fonctions et services écosystémiques ____________________________________________ 2

1.1. La création de galeries _____________________________________________________________ 3

1.2. Bioturbation et évolution de la matière organique ________________________________________ 3

1.2.1. L’alimentation et les rejets ______________________________________________________ 3

1.2.2. La création de middens _________________________________________________________ 5

1.3. Interaction avec d’autres organismes __________________________________________________ 5

2. Effet des pratiques agricoles sur la démographie des populations lombriciennes ________ 6

2.1. Effets défavorables aux vers de terre __________________________________________________ 7

2.1.1. Diminution de la ressource en carbone _____________________________________________ 7

2.1.2. Travail du sol, pesticides et tassement _____________________________________________ 8

2.1.2.1. Le labour ________________________________________________________________ 8

2.1.2.2. L’utilisation de pesticides ___________________________________________________ 9

2.1.2.3. Le tassement du sol _______________________________________________________ 10

2.2. Effets favorables aux vers de terre ___________________________________________________ 10

3. Biologie et dynamique des populations de lombriciens _____________________________ 12

3.1. Le cycle de vie __________________________________________________________________ 12

3.2. Les facteurs du milieu influençant le cycle de vie _______________________________________ 13

3.2.1. La température et l’humidité du sol ______________________________________________ 14

3.2.2. La matière organique _________________________________________________________ 14

3.2.3. Le pH et le type de sol ________________________________________________________ 15

4. Démarche de la thèse ________________________________________________________ 16

Chapitre 2 –Méthode de prélèvement des communautés lombriciennes __ 18

1. Introduction ________________________________________________________________ 20

2. Materials and methods _______________________________________________________ 21

2.1. Sites and cropping systems _________________________________________________________ 21

2.2. Experimental design and earthworm sampling methods __________________________________ 21

2.3. Chemicals ______________________________________________________________________ 22

2.4. Statistical analysis________________________________________________________________ 22

3. Results ____________________________________________________________________ 23

3.1. Species and age class composition of the earthworm community ___________________________ 23

3.2. Comparison of expellant effect in the simple method ____________________________________ 23

3.3. Comparison of expellant effect in the combined method __________________________________ 24

4. Discussion _________________________________________________________________ 24

Chapitre 3 - WORMDYN : Un modèle de dynamique de la population de

Lumbricus terrestris en champ cultivé _____________________________ 27

1. Introduction ________________________________________________________________ 30

2. Materials and methods _______________________________________________________ 32

2.1. The WORMDYN model___________________________________________________________ 32

2.2. Parameter values _________________________________________________________________ 35

2.2.1. Boundaries of the environmental condition classes __________________________________ 35

2.2.2. Lefkovitch Matrix parameters __________________________________________________ 36

2.2.2.1. Survival (CC1) and hatching (CJ1) of cocoons __________________________________ 36

2.2.2.2. Juvenile survival (JJ1) and development to sub-adults (JS1) ________________________ 37

2.2.2.3. Sub-adult survival (SS1) and development to adults (SA1) _________________________ 37

2.2.2.4. Adult survival (AA1) ______________________________________________________ 38

2.2.2.5. Fecundity (AC1) _________________________________________________________ 38

2.3. Assessment of the model predictions _________________________________________________ 39

2.3.1. Data _______________________________________________________________________ 39

2.3.2. Model predictions ____________________________________________________________ 40

2.4. Sensitivity analysis principle _______________________________________________________ 41

3. Results and discussion _______________________________________________________ 42

3.1. Model predictions ________________________________________________________________ 42

3.2. Sensitivity analysis _______________________________________________________________ 44

4. Conclusion _________________________________________________________________ 45

Chapitre 4 : Etude de l’impact de systèmes de culture sur les communautés

lombriciennes ; analyse du comportement de WORMDYN ____________ 46

1. Structure de la communauté de vers de terre en systèmes conventionnel, biologique et sous

couvert végétal vivant permanent. Évaluation pendant trois ans dans un essai de longue

durée. _______________________________________________________________________ 50

1.1. Introduction ____________________________________________________________________ 52

1.2. Materials and methods ____________________________________________________________ 53

1.2.1. Site and cropping systems _____________________________________________________ 53

1.2.2. Earthworm sampling method ___________________________________________________ 54

1.2.3. Statistical analysis ____________________________________________________________ 54

1.3. Results and discussion ____________________________________________________________ 55

1.3.1. Earthworm species ___________________________________________________________ 55

1.3.2. Year sampling effect __________________________________________________________ 55

1.3.3. Cropping system effect ________________________________________________________ 56

1.3.3.1. Diversity _______________________________________________________________ 56

1.3.3.2. Density and biomass ______________________________________________________ 56

1.4. Conclusion _____________________________________________________________________ 59

2. Analyse du comportement du modèle WORMDYN sur les données de La Cage. _______ 60

2.1. Présentation des données climatiques utilisées __________________________________________ 60

2.2. Comportement de WORMDYN _____________________________________________________ 61

2.3. Discussion______________________________________________________________________ 61

Discussion générale et perspectives ________________________________ 64

1. Echantillonnage des communautés lombriciennes ________________________________ 67

1.1. Limites liées à la méthode d’échantillonnage ___________________________________________ 67

1.2. Période d’échantillonnage pour l’initialisation de WORMDYN ____________________________ 68

2. Amélioration de la qualité prédictive de WORMDYN _____________________________ 68

2.1. Structure du modèle ______________________________________________________________ 69

2.1.1. Augmentation du nombre de classes démographiques ________________________________ 69

2.1.2. Modification du pas de temps ___________________________________________________ 69

2.2. Paramétrisation du modèle _________________________________________________________ 70

2.2.1. Ajout de classes de température et d’humidité ______________________________________ 70

2.2.2. Prise en compte de la ressource trophique et des relations de compétition ________________ 70

2.2.3. Prise en compte des effets directs des pratiques culturales _____________________________ 71

2.2.4. Effet de seuils de température et d’humidité _______________________________________ 72

2.2.5. Paramétrisation avec expérience d’élevage ________________________________________ 72

2.2.6. Application du modèle à d’autres espèces _________________________________________ 74

Statistiques de consultation

Repository Staff Only: edit this item