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Le Bayon, Renée-Claire
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Le Bayon, Renée-Claire
Affiliation principale
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claire.lebayon@unine.ch
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- PublicationAccès libreTopsoil structure stability in a restored floodplain: Impacts of fluctuatingwater levels, soil parameters and ecosystem engineers(2017-6)
; ; ; ; Ecosystem services provided byfloodplains are strongly controlled by the structural stability of soils. The developmentof a stable structure infloodplain soils is affected by a complex and poorly understood interplay of hydrological,physico-chemical and biological processes. This paper aims at analysing relations betweenfluctuating groundwaterlevels, soil physico-chemical and biological parameters on soil structure stability in a restoredfloodplain. Water levelfluctuations in the soil are modelled using a numerical surface-water–groundwaterflow model and correlated tosoil physico-chemical parameters and abundances of plants and earthworms. Causal relations and multiple interactionsbetween the investigated parameters are tested through structural equation modelling (SEM). Fluctuating water levelsin the soil did not directly affect the topsoil structure stability, but indirectly through affecting plant roots and soil pa-rameters that in turn determine topsoil structure stability. These relations remain significant for mean annual days ofcomplete and partial (N25%) water saturation. Ecosystem functioning of a restoredfloodplain might already be affectedby thefluctuation of groundwater levels alone, and not only through completeflooding by surface water during afloodperiod. Surprisingly, abundances of earthworms did notshow any relation to other variables in the SEM. Thesefindingsemphasise that earthworms have efficiently adapted to periodic stress and harsh environmental conditions. Variabilityof the topsoil structure stability is thus stronger driven by the influence offluctuating water levels on plants than by theabundance of earthworms. This knowledge about the functional network of soil engineering organisms, soil parametersandfluctuating water levels and how they affect soil structural stability is of fundamental importance to define man-agement strategies of near-natural or restoredfloodplains in the future. - PublicationAccès libreEarthworm surface casts affect soil erosion by runoff water and phosphorus transfer in a temperate maize crop(2001)
; Binet, FrançoiseTo test the hypothesis that earthworm surface casts contribute to soil erosion and nutrient transfers in a temperate maize crop, two rainfall experiments were set up. One was focused on the erodibility of earthworm casts, the second examined in how casts affect water runoff and nutrient transfers. Casts produced from anecic and endogeic earthworm species were both analyzed. Visual observations in the field showed no cast transport but only cast disintegration and transfers of particles. Erodibility of newly deposited casts was high and differed significantly between age groups. Cast erosion was significantly positively related to initial mass when young but not when old. The paradox is that despite a high cast abundance (25% of the area) and obvious cast erosion, amounts of sediment and nutrient losses (C, N and P) in the runoff were at least twice as high without, than in the presence of, surface casts. Earthworm activities were shown to act as a physical brake for soil erosion by (i) creating a surface roughness with the deposition of surface casts and (ii) reducing water runoff by associated enhanced water percolation. Once the breaking-down point of the physical resistance of casts was reached, all surface casts were quickly disintegrated and finally completely washed away. The amount of particulate phosphorus recovered in water runoff was 34.7 mg P m−2, while 128.5 mg P m−2 was estimated to have been released from casts. The transfers were found to occur over a short-distance through successive deposition/suspension of soil particles in the water runoff. - PublicationAccès libreRainfall effects on erosion of earthworm casts and phosphorus transfers by water runoff(1999)
; Binet, F.We investigated whether, under a temperate climate and in a maize crop, earthworm casts could contribute to soil erosion and further favour the exportation of phosphorus by runoff waters. Recording of casts was made in compacted (wheel-tracks) and non-compacted inter-rows, for a 2-month period in spring. To assess the rainfall impact on cast evolution, half of the observation sites were protected against rain splash by a nylon mesh placed above the soil surface. The water runoff was collected and analysed for sediment contents and phosphorus concentration. The mean annual production of surface casts was calculated to be 34 kg (dry weight) year–1 kg–1 earthworm (fresh weight). Synchronization between cast erosion and rainfall events was shown under natural conditions (unprotected sites). The erosion rate was 4 times greater over rainy periods than dry ones, reaching 80% of cast numbers. It appeared that not the runoff effect but the splash effect, due to the kinetics of the drops, disrupted casts. Newly formed casts disappeared first, with the erosion rate decreasing twofold for casts more than 10 days old. Cast erosion and runoff, as well as worm casting activity, were greater under compacted sites than under non-compacted sites, indicating an influence of earthworms on soil erosion from compacted soils. The total phosphorus content was similar in casts and uningested soil (0.80 mg phosphorus g–1). Potential phosphorus losses from cast erosion was calculated to reach 25–49 mg phosphorus m–2 per rainfall event depending on soil compaction. The amounts of particulate phosphorus recovered in water runoff after each rainfall event varied from 1 mg to 11 mg phosphorus. These results are compared and discussed.