, L'érodibilité d'un sol est une propriété dynamique que les modèles d'érosion doivent considérer

, Comme nous l'avons énoncé précédemment, la stabilité structurale est un proxy de

, pas de stimulation de l'activité microbienne par des apports), les variations de la stabilité structurale de la surface du sol à pas de temps court étaient essentiellement influencées par la dynamique de la teneur en eau du sol. La teneur en eau du sol au prélèvement, l'histoire hydrique et l'histoire des précipitations sont apparus comme des 'est pas stimulée. Ces facteurs sont impliqués dans différents processus physicochimiques liés aux cycles d'humidité. Ces processus physico-chimiques, Les variations à pas de temps court de la stabilité structurale de la surface du sol sont influencées par la dynamique de la teneur en eau Les résultats présentés dans le chapitre 4 montrent que, pour les conditions étudiées

, Si la sub-surface du sol présentait de fortes variations de stabilité structurale, aucune des variables étudiées n'a permis d'expliquer ces variations. L'identification des facteurs

, Les facteurs abiotiques contrôlent la stabilité structurale au travers de processus physico-chimiques

. Tisdall, Ces facteurs sont impliqués dans des processus physico-chimiques. 3.1. 3.1. 3.1. 3.1. Les processus physico-chimiques de variation de la stabilité structurale sont liés (environ 3 h pour l'humectation et 5 jours pour la dessiccation). De tels cycles d'humidité n'ont pas fait varier la stabilité structurale, Les facteurs de variation de la stabilité structurale à pas de temps court sont des variables abiotiques liées à la teneur en eau du sol, 1978.

. Barzegar, l'influence des cycles d'humidité sur la, 1995.

, Un état des connaissances variable selon les processus La synthèse bibliographique présentée dans le chapitre 2 a montré que l'état des connaissances concernant les processus physico-chimiques de variation de la stabilité structurale présentait des statuts variables. A l'échelle du macro-agrégat, les processus identifiés (éclatement, impact des gouttes de pluies, gel-dégel, gonflement différentiel des argiles) ont été observés et leurs conditions d'occurrence sont largement connues. A l'échelle du micro-agrégat, certains processus sont biens maitrisés (dispersion/floculation des argiles) mais d'autres nécessitent de nouvelles études pour valider leur occurrence et leur implication dans les variations de stabilité structurale. C'est le cas par exemple du réarrangement particulaire intra-agrégat

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, Baptiste ALGAYER Variabilité à court terme de la stabilité structurale des sols et processus physico chimiques associés Résumé

, Afin d'améliorer les connaissances sur les facteurs et processus contrôlant la stabilité structurale, cette thèse avait pour objectif d'étudier la variabilité de la stabilité structurale à pas de temps court (quelques jours) ainsi que les processus physico-chimiques qui en sont à l'origine. Des études de terrain ont permis de caractériser une dynamique rapide de la stabilité structurale pour un sol donné avec notamment : des différences importantes entre surface et sub-surface, La stabilité structurale du sol peut être utilisée pour estimer l'érodibilité du sol, paramètre clef des modèles d'érosion

, Une synthèse bibliographique a montré que l'occurrence de certains de ces processus nécessitait d'être vérifiée, notamment pour le réarrangement particulaire. Des expérimentations en laboratoire ont montré que la structure interne des agrégats était affectée pas les cycles d'humidité à l'échelle millimétrique comme micrométrique. Cependant, les réarrangements de particules observés n'ont pas pu être strictement reliés aux variations de stabilité structurale. Les résultats de ces expérimentations confirment le suivi de terrain : la teneur en eau du sol a un rôle majeur dans les variations de stabilité structurale à pas de temps court

, Mots clés : sol, stabilité structurale, érodibilité, agrégation, réarrangement particulaire, teneur en eau Short time step variability of soil aggregate stability and physico-chemical processes involved