Spatial organization of the plant-soil system

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Table of contents

I. Introduction et synthèse bibliographique 
Introduction Générale
1. Integrating plant control of nutrient cycling within root foraging strategies 
1.1. Introduction
1.2. Plants ability to control nutrient cycling
1.2.1. Direct control of nutrient availability
1.2.2. Interaction with soil microbes
1.2.3. Interaction with large herbivores
1.3. The spatial and temporal scales of plant-soil interactions
1.3.1. The rhizosphere
1.3.2. The below-ground zone of inuence
1.3.3. The above-ground zone of inuence
1.3.4. Extended above-ground zone of inuence
1.4. Linking plant control of nutrient cycling to root foraging strategies
1.4.1. Root traits involved in root foraging strategies
1.4.2. Relationships between local root density and soil functioning
1.4.3. Root foraging strategies at the whole plant scale: hypothesis of a trade-o between soil exploration and occupation
1.5. Conclusions
II. Pourquoi et quand les plantes devraient-elles limiter l’exploration du sol par leurs racines ? 
2. Why and when should plant limit the exploration of soil by their roots? 
2.1. Abstract
2.2. Introduction
2.3. Material and Methods
2.3.1. Models descriptions
2.3.1.1. Spatial organization of the plant-soil system
2.3.1.2. Compartments of the nutrient cycle
2.3.1.3. Nutrient uxes in the plant-soil system
2.3.1.4. Model without nutrient uxes between unoccupied and occupied soil
2.3.1.5. Model considering a spatial dynamic of the zones of inuence .
2.3.1.6. The consequences of space exploration on nutrient cycling parameters
2.3.2. Parametrisation
2.3.3. Partial recycling eciencies and system closure
2.4. Results
2.4.1. Equilibrium and stability conditions
2.4.2. Conditions for which a reduced explorations optimizes plant biomass
2.4.3. Consequences of reduced soil exploration on the plant-soil system functioning
2.4.4. Role of the spatial dynamics between occupied and unoccupied soil .
2.5. Discussion
2.5.1. When is it benecial for plants to reduce soil exploration by roots?
2.5.2. Generality of model predictions
2.5.3. Potential applications
Perspectives
III. Patrons d’exploration racinaire, eet îlot de fertilité et cycle de l’azote chez trois espèces de Poacées pérennes de savane. 
3. Root exploration pattern and nutrient cycling in the plants-soil system of three savanna grasses 
3.1. Abstract
3.2. Introduction
3.3. Material and Methods
3.3.1. Study site
3.3.2. Experimental design
3.3.3. Sampling procedure
3.3.3.1. Quadrat selection
3.3.3.2. Roots and soil sampling
3.3.4. Analyses performed
3.3.5. Statistics
3.4. Results
3.4.1. Aboveground biomass pattern
3.4.2. Belowground exploration pattern
3.4.3. Soil content in C, N and P
3.4.4. Nitrogen cycling (plant and soil N stock and 15N)
3.5. Discussion
3.5.1. Plant soil exploration strategies
3.5.2. Absence of island of fertility eect ?
3.5.3. Species eects on nitrogen cycling
3.5.4. Conclusion
3.6. Acknowledgement
Perspectives
IV. Modélisation de l’impact de la distribution racinaire sur le contrôle du recyclage des nutriments à l’échelle de la rhizosphère et de la zone d’inuence souterraine 
4. Modelling the impact of root distribution on the control of nutrient availability at the rhizosphere scale 
4.1. Abstract
4.2. Introduction
4.3. Material & Methods
4.3.1. Model Description
4.3.2. Numerical analysis
4.3.3. Upscaling rhizospheres to the below-ground zone of inuence
4.4. Results
4.4.1. Root density eects on nutrient uptake at the centimetre scale
4.4.2. Rhizosphere sizes as predictors of root interactions
4.4.3. Root foraging at the scale of the below-ground zone of inuence
4.5. Discussion
4.5.1. Inter-root competition and facilitation
4.5.2. Inferring optimal root strategies
4.5.3. The exploration/occupation trade-o
4.5.4. Conclusion
4.6. Acknowledgement
5. Discussion Générale 
5.1. Stratégies d’exploration racinaire et cycles des nutriments
5.1.1. Compétition et facilitation racinaire
5.1.2. Intégration des interactions racinaires à l’échelle de la zone d’inuence racinaire
5.1.3. Confrontation aux plantes réelles
5.1.4. Le compromis exploration/occupation : un outil heuristique pertinent ? .
5.2. Généralisation : stratégies d’acquisition des ressources et rétroactions plante-sol .
5.2.1. Un autre mode d’acquisition des ressources : les associations
5.2.2. Spécicité des interactions entre les plantes et les microorganismes du sol
5.2.3. Les rétroactions plantes-sol à l’échelle de la communauté de plantes
5.2.4. Application aux agro-écosystèmes ?
5.3. Conclusion
Bibliography 
V. Annexes 
6. Appendix to Chapter 2 
6.1. Equations and stability conditions for model 2
6.1.1. Model description
6.1.2. Stability of the equilibrium
6.2. Trade-os equations and parameterization of the model
6.2.1. Trade-o equations
6.2.2. Parameterization
6.2.3. trade-o calibration
6.3. Detailed analysis of model 1 with a functional trade-o between exploration and uptake
6.3.1. Stability conditions
6.3.2. Calculation of optimal soil exploration xP
6.3.3. Variation of soil nutrient stocks D and N with soil exploration x
6.3.4. Variation of total nutrient stocks T with soil exploration x
6.4. Generalization of the results of model 1 for other trade-os
6.4.1. Functional trade-o between soil exploration and mineralization
6.4.2. Functional trade-o between soil exploration and lixiviation
6.4.3. Coupled trade-os
7. Appendix to Chapter 3 
7.1. Root scan analysis
7.2. Patterns of root exploration
7.3. Soil content in C and nutrients
7.4. plant and soil C:N
7.5. N isotopic data
8. Appendix to chapter 4 
8.1. Relationships between root length density and uxes of phosphorus whithin the soil
8.2. Relationship between root length density nroot and rhizP =rhizS
8.3. Upscaling to the whole plant
Résumé