Régulations biotiques et abiotiques de la décomposition des matières organiques des sols

Abstract : Soils represent the principal reservoir of carbon with two times as much carbon as is found in the atmospheric pool. In an effort to better predict and anticipate how soil carbon dynamics will be affected by environmental changes and by the evolution of cropping systems, it is necessary to better understand the processes that regulate soil organic matter decomposition. This study aims to investigate two regulatory mechanisms of the soil carbon dynamic: the properties of the microbial habitat and the ones of the microbial communities. Because they are directly affected by the climatic changes and by the rapid evolution of cropping systems these two mechanisms appear to have a key role in the regulation of soil carbon decomposition. Experimental designs were setup allowing the variations, independent or simultaneous, of the properties of microbial habitat and the ones of the microbial communities. First, to assess the relative importance of soil structure, microcosms with different gradient of disaggregation were incubated. Then, to assess the relative importance of diversity erosion, microcosms with microbial diversity gradient were incubated. Finally, using contrasted soils varying in their habitats and their microbial communities properties, we aimed to hierarchize these two carbon decomposition regulatory mechanisms.The obtained results indicate that microbial activity of soil organic carbon decomposition seems to be more controlled by environmental conditions (such as pH, texture and also substrate supply) than by the microbial community structure or metabolic profiles. Then we observed that organic carbon mineralisation was impacted only when the levels of diversity were very low suggesting the existence of a threshold, and that the functional redundancy is maybe not as great as numerous studies suggest. Moreover, our work showed that when conditions of aeration in the pore system are sufficient, mechanisms regulating the dynamic of soil organic carbon take place at fine spatial scales.
Document type :
Theses
Complete list of metadatas

Cited literature [202 references]  Display  Hide  Download

https://pastel.archives-ouvertes.fr/pastel-01049725
Contributor : Abes Star <>
Submitted on : Friday, July 25, 2014 - 2:12:08 PM
Last modification on : Wednesday, September 4, 2019 - 1:52:10 PM
Long-term archiving on : Tuesday, November 25, 2014 - 6:02:41 PM

File

DLE_ManuscritTheseJUAREZVF.pdf
Version validated by the jury (STAR)

Identifiers

  • HAL Id : pastel-01049725, version 1

Citation

Sabrina Juarez. Régulations biotiques et abiotiques de la décomposition des matières organiques des sols. Sciences agricoles. AgroParisTech, 2013. Français. ⟨NNT : 2013AGPT0031⟩. ⟨pastel-01049725⟩

Share

Metrics

Record views

1574

Files downloads

1791