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Le Bayon, Renée-Claire

Nom
Le Bayon, Renée-Claire
Affiliation principale
Email
claire.lebayon@unine.ch
Identifiants
https://libra.unine.ch/handle/123456789/319
_
0000-0002-1237-497X

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  • Publication
    Accès libre
    Lumbricid macrofauna alter atrazine mineralization and sorption in a silt loam soil
    (2006)
    Binet, Françoise
    ;
    Anne Kersanté
    ;
    Munier-Lamy, Colette
    ;
    Le Bayon, Renée-Claire 
    ;
    Belgy, Marie-José
    ;
    Shipitalo, Martin J.
    Atrazine is a widely used herbicide and is often a contaminant in terrestrial and freshwater ecosystems. It is uncertain, however, how the activity of soil macrofauna affects atrazine fate and transport. Therefore, we investigated whether earthworms enhance atrazine biodegradation by stimulating herbicide degrading soil microflora, or if they increase atrazine persistence by facilitating herbicide sorption. Short (43 d) and medium term (86 d) effects of the earthworms Lumbricus terrestris and Aporrectodea caliginosa on mineralization, distribution, and sorption of U-ring-14C atrazine and on soil C mineralization was quantified in packed-soil microcosms using silt loam soil. A priming effect (stimulation of soil C mineralization) caused by atrazine supply was shown that likely lowered the earthworm net effect on soil C mineralization in atrazine-treated soil microcosms. Although earthworms significantly increased soil microbial activity, they reduced atrazine mineralization to 14CO2–C from15.2 to 11.7% at 86 d. Earthworms facilitated formation of non-extractable atrazine residues within C-rich soil microsites that they created by burrowing and ingesting soil and organic matter. Atrazine sorption was highest in their gut contents and higher in casts than in burrow linings. Also, gut contents exhibited the highest formation of bound atrazine residues (non-extractable atrazine). Earthworms also promoted a deeper and patchier distribution of atrazine in the soil. This contributed to greater leaching losses of atrazine in microcosms amended with earthworms (3%) than in earthworm-free microcosms (0.003%), although these differences were not significant due to high variability in transport from earthworm-amended microcosms. Our results indicated that earthworms, mainly by casting activity, facilitated atrazine sorption, which increased atrazine persistence. As a consequence, this effect overrode any increase in atrazine biodegradation due to stimulation of microbial activity by earthworms. It is concluded that the affect of earthworms of atrazine mineralization is time-dependent, mineralization being slightly enhanced in the short term and subsequently reduced in the medium term.
  • Publication
    Accès libre
    Annual variations in earthworm surface-casting activity and soil transport by water runoff under a temperate maize agroecosytem
    (Elsevier, 2002)
    Le Bayon, Renée-Claire 
    ;
    Corrie Moreau
    ;
    Chantal Gascuel-odoux
    ;
    Binet, Françoise
    Investigations were conducted on both the annual patterns of earthworm casting activity and the annual variations in soil and phosphorus (P) transfers by water runoff, under a temperate maize crop, to determine whether there is any time synchronism over the year between these processes that could increase risk of soil erosion. Cast dynamics were measured at 15-day intervals for 1 year. Phosphorus forms were determined in runoff waters and the sediments collected were analyzed for nitrogen (N), carbon (C) and P contents. As long as there was no crust at the soil surface, no runoff was observed. Once the sealing crust formed, the soil erosion began. After the rainstorm events in August, soil erosion already reached 70% of the total soil loss that occurred over the crop year. A total of 140 g m−2 year−1 of sediment was lost by the end of the year. A time synchronization was observed between tillage practices and highest cast productions over the year, which were then interrupted for up to 5 weeks after both ploughing and crop harvest. In particular, the absence of anecic casts onto the soil till September underline that Lumbricus terrestris was most affected by ploughing. The likelihood that earthworm casts contributed to soil erosion was enforced by the correlation between the timing of cast disappearance and the increase in sediment transfers for rainstorm events observed in summer, as well as for long rainy period in fall/winter. However, we could not outline a systematic correlation over the year but just for defined periods. Particulate soil erosion and P amounts in runoff waters decreased (55–2 g m−2, and 19–5 mg of P losses m−2, respectively) through the crop year. However, the content of organic matter in sediment increased (2.54–5.16%) compared to the initial soil (1.8%), as well as the P concentration (1.1–1.6 mg g−1).