Lumbricina

Résumé

vignette|redresse=2|Les vers de terre font partie des détritivores qui interviennent dans le cycle biogéochimique de la matière organique en tant qu'agents de l'humification et de la minéralisation du carbone et de l'azote. vignette|redresse=2|Les lombrics jouent un rôle important dans le cycle du carbone organique des sols qui stockent plus de de tonnes de carbone par an. Leur bioturbation favorise la pénétration de l'air et de l'eau et leur rôle de décomposeur contribue à la formation des nutriments nécessaires aux plantes environnantes et au microbiote tellurique. Constituant 60 à 80 % de la biomasse animale des sols, ils émettent des gaz à effet de serre (, ) via leur système digestif. Ingérant sans cesse de la terre et des résidus végétaux riches en microbes, ce sont en fait les micro-organismes de leur microbiote intestinal qui décomposent les débris végétaux et produisent ces gaz. Plusieurs études évaluent le compromis entre l'effet bénéfique des lombrics sur la séquestration d

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Earthworm communities in alluvial forests: Influence of altitude, vegetation stages and soil parameters

Géraldine Michèle Bullinger, Jean-Michel Gobat, Claire Guenat, Renée-Claire Le Bayon

In many terrestrial ecosystems, soil parameters usually regulate the distribution of earthworm communities.In alluvial ecosystems, few studies have investigated the impact of periodic floods and alluvium deposition on soil fauna. In this context, we assumed that earthworm communities may vary depending on altitude (alpine, subalpine, mountain and hill levels), forest successional stage (post-pioneer to mature forests) and some soil parameters. Our results demonstrated that the composition of earthworm communities differed depending on altitudinal gradients. No earthworm was found at the alpine level while maximum density and biomass were observed at the hill level mainly due to the contribution of anecic species. A total of 27 species and subspecies were found over the three sampling sites, and Lumbricus moliboeus was discovered for the first time in carbonated soils. Soil texture had a major effect on epigeics that were often associated with coarse sandy texture in contrast to anecics which preferred deep soils and mature forest stages, which in combination provided the highest carbon content and the finest soil texture. In our study, carbonated fluviosols (Fluvisols according to the World Reference Base) were recorded; fluviosols typiques with well-structured A layers were generally found in mature or intermediate forest stages while most of fluviosols juveniles with heterogeneous texture were observed principally in post-pioneer forests. We conclude that in alluvial ecosystems, earthworm communities were highly dependent first on soil parameters, then altitude and to a lesser extent forest successional stages. Changes in earthworm communities tend to reflect a gradient of alluvial dynamics thus reinforcing the potential role of earthworms as bioindicators in natural and/or semi natural alluvial ecosystems.

Elsevier2011

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Earthworms are considered as key actors of soil processes at different spatial and temporal scales and provide essential ecosystem services linked to climate regulation or primary production. However, little is known about their basic functional roles (e.g. organic matter decomposition, soil structuring processes) in perturbed systems such as urban or alluvial soils. Alluvial soils are characterized by regular physical perturbation through flooding and associated erosion/sedimentation processes which are rather similar to perturbations (e.g. temporal instability, spatial heterogeneity) affecting urban soils. Due to their close soil characteristics, we hypothesized that in both cases, soil functioning is similar with respect to soil fauna activity. Under controlled conditions, our objective was to investigate the effects of two endogeic earthworm species, Allolobophora chlorotica (pink morph) and Aporrectodea rosea (the two most abundant species found in the studied urban site), on soil organic matter (SOM) dynamics and soil structure (network of earthworm burrows) comparing an urban and an alluvial soil. We investigated the growth of individuals (weight gain and reproduction success) and assessed their effects on SOM decomposition (cumulative C–CO2 emission, nitrogen and phosphorus mineralization) and soil structure (macroporosity, total length and connectivity of segments) after one and three months of incubation. Our results showed higher growth of A. rosea in the alluvial soil compared to the urban soil. However, the total length of burrows, carbon and nitrogen mineralization were often higher in the urban soil especially when the two species were combined. This trend can be mainly explained by lower organic matter content found in the urban soil which may influence positively the burrowing activity and negatively the growth of earthworms. Endogeic earthworms appear a key feature of the soil functioning in the urban context through their roles on organic matter transformation, the formation and maintenance of the soil structure.

Elsevier2015

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Composition and superposition of alluvial deposits drive macro-biological soil engineering and organic matter dynamics in floodplains

Claire Guenat, Renée-Claire Le Bayon, Rodolphe Schlaepfer, Andreas Cedric Schomburg, Pascal Turberg

Soil structure formation in alluvial soils is a fundamental process in near-natural floodplains. A stable soil structure is essential for many ecosystem services and helps to prevent river bank erosion. Plants and earthworms are successful soil engineering organisms that improve the soil structural stability through the incorporation of mineral and organic matter into soil aggregates. However, the heterogeneous succession of different textured mineral and buried organic matter layers could impede the development of a stable soil structure. Our study aims at improving the current understanding of soil structure formation and organic matter dynamics in near natural alluvial soils. We investigate the effects of soil engineering organisms, the composition, and the superimposition of different alluvial deposits on the structuration patterns, the aggregate stability, and organic matter dynamics in in vitro soil columns, representing sediment deposition processes in alluvial soils. Two successions of three different deposits, silt-buried litter-sand, and the inverse, were set up in mesocosms and allocated to four different treatments, i.e. plants, earthworms, plants + earthworms, and a control. X-ray computed tomography was used to identify structuration patterns generated by ecosystem engineers, i.e. plant root galleries and earthworm tunnels. Organic matter dynamics in macro-aggregates were investigated by Rock-Eval pyrolysis. Plant roots only extended in the top layers, whereas earthworms preferentially selected the buried litter and the silt layers. Soil structural stability measured via water stable aggregates (%WSA) increased in the presence of plants and in aggregates recovered from the buried litter layer. Organic matter dynamics were controlled by a complex interplay between the type of engineer, the composition (silt, sand, buried litter) and the succession of the deposits in the mesocosm. Our results indicate that the progress and efficiency of soil structure formation in alluvial soils strongly depends on the textural sequences of alluvial deposits.

2019

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Earthworm communities in alluvial forests: Influence of altitude, vegetation stages and soil parameters

Géraldine Michèle Bullinger, Jean-Michel Gobat, Claire Guenat, Renée-Claire Le Bayon

Elsevier2011

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Elsevier2015

Composition and superposition of alluvial deposits drive macro-biological soil engineering and organic matter dynamics in floodplains

Claire Guenat, Renée-Claire Le Bayon, Rodolphe Schlaepfer, Andreas Cedric Schomburg, Pascal Turberg

2019