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Le Bayon, Renée-Claire
Nom
Le Bayon, Renée-Claire
Affiliation principale
Email
claire.lebayon@unine.ch
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3 Résultats
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- PublicationAccès libreCoupling X-ray computed tomography and freeze-coring for the analysis of fine-grained low-cohesive soils(2017-12-15)
; ; This paper presents the coupling of freeze-core sampling with X-ray CT scanning for the analysis of the soil structure of fine-grained, low-cohesive soils. We used a medical scanner to image the 3D soil structure of the frozen soil cores, providing X-ray CT data at a millimetric resolution over freeze-cores that are up to 62.5 cm long and 25 cm wide. The obtained data and the changes in gray level values could be successfully used to identify and characterize different soil units with distinctly different physical properties. Traditional measurements of soil bulk density, carbon and particle size analyses were conducted within each of the identified soil units. These observations were used to develop a 3D model of soil bulk density and organic matter distribution for five freeze-cores obtained at a restored floodplain in Switzerland. The millimetric X-ray CT scanning was applied to detect the impact of freeze-coring on the soil structural integrity. This allows identifying undisturbed zones, a critical precondition for any subsequent assessment of soil structure. The proposed coupling is thought to be applicable to a wide range of other low-cohesive soil types and has a large potential for applications in hydrogeology, biology or soil science. - PublicationAccès libreImpact of roots, mycorrhizas and earthworms on soil physical properties as assessed by shrinkage analysis(2009)
; ; Boivin, P.Soil biota such as earthworms, arbuscular mycorrhizal fungi (AMF) and plant roots are known to play a major role in engineering the belowground part of the terrestrial ecosystems, thus strongly influencing the water budget and quality on earth. However, the effect of soil organisms and their interactions on the numerous soil physical properties to be considered are still poorly understood. Shrinkage analysis allows quantifying a large spectrum of soil properties in a single experiment, with small standard errors. The objectives of the present study were, therefore, to assess the ability of the method to quantify changes in soil properties as induced by single or combined effects of leek roots (Allium porrum), AMF (Glomus intraradices) and earthworms (Allolobophora chlorotica). The study was performed on homogenised soil microcosms and the experiments lasted 35 weeks. The volume of the root network and the external fungal hyphae was measured at the end, and undisturbed soil cores were collected. Shrinkage analysis allowed calculating the changes in soil hydro-structural stability, soil plasma and structural pore volumes, soil bulk density and plant available water, and structural pore size distributions. Data analysis revealed different impacts of the experimented soil biota on the soil physical properties. At any water content, the presence of A. chlorotica resulted in a decrease of the specific bulk volume and the hydro-structural stability around 25%, and in a significant increase in the bulk soil density. These changes went with a decrease of the structural pore volumes at any pore size, a disappearing of the thinnest structural pores, a decrease in plant available water, and a hardening of the plasma. On the contrary, leek roots decreased the bulk soil density up to 1.23 g cm−3 despite an initial bulk density of 1.15 g cm−3. This increase in volume was accompanied with a enhanced hydro-structural stability, a larger structural pore volume at any pore size, smaller structural pore radii and an increase in plant available water. Interestingly, a synergistic effect of leek roots and AMF in the absence of the earthworms was highlighted, and this synergistic effect was not observed in presence of earthworms. The structural pore volume generated by root and AMF growth was several orders of magnitude larger than the volume of the organisms. Root exudates as well as other AMF secretion have served as carbon source for bacteria that in turn would enhance soil aggregation and porosity, thus supporting the idea of a self-organization of the soil–plant–microbe complex previously described. - PublicationAccès libreCoupling X-ray computed tomography and freeze-coring for the analysis of fine-grained low-cohesive soils
; This paper presents the coupling of freeze-core sampling with X-ray CT scanning for the analysis of the soil structure of fine-grained, low-cohesive soils. We used a medical scanner to image the 3D soil structure of the frozen soil cores, providing X-ray CT data at a millimetric resolution over freeze-cores that are up to 62.5 cm long and 25 cm wide. The obtained data and the changes in gray level values could be successfully used to identify and characterize different soil units with distinctly different physical properties. Traditional measurements of soil bulk density, carbon and particle size analyses were conducted within each of the identified soil units. These observations were used to develop a 3D model of soil bulk density and organic matter distribution for five freeze-cores obtained at a restored floodplain in Switzerland. The millimetric X-ray CT scanning was applied to detect the impact of freeze-coring on the soil structural integrity. This allows identifying undisturbed zones, a critical precondition for any subsequent assessment of soil structure. The proposed coupling is thought to be applicable to a wide range of other low-cohesive soil types and has a large potential for applications in hydrogeology, biology or soil science.