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Le Bayon, Renée-Claire
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Le Bayon, Renée-Claire
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claire.lebayon@unine.ch
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Voici les éléments 1 - 10 sur 93
- PublicationAccès libreThe relative contribution of the five pedogenesis factors to soil formation and soil organic matter incorporation across environmental gradients(Neuchâtel : Université de Neuchâtel, 2024)
; ; Le changement climatique devrait remettre en question la persistance future du carbone organique du sol (SOC) dans les écosystèmes terrestres. Compte tenu de la complexité de l'évolution du carbone organique du sol, les interactions plante-sol, les conditions climatiques et les facteurs biotiques sont essentiels pour comprendre le fonctionnement des écosystèmes et la formation des sols. Au cours des dernières décennies, le changement climatique induit par l'homme, la destruction des habitats et les perturbations écologiques ont entraîné des changements significatifs dans la dynamique socio-environnementales, ce qui s'est traduit par une modification des propriétés des sols et de la dynamique des écosytèmes. Ces changements devraient avoir un impact majeur sur les services que les sols rendent à l'homme, menaçant la persistance de nombreuses espèces et, par conséquent, la santé globale des écosystèmes. L'étude des changements du SOC dans un monde en mutation est cruciale pour la compréhension des systèmes environnementaux contemporains. Dans cette thèse, j'ai d'abord cherché à comprendre comment les changements d'environnement entraînent des changements de SOC dans les sols au fil des décennies, en examinant les sols du point de vue d'un gradient environnemental, des rives des lacs aux prairies alpines. Deuxièmement, j'ai étudié comment les conditions environnementales changeantes - en utilisant les gradients d'altitude - conduisent la dynamique de décomposition de la matière organique dans le contexte du changement climatique. La dynamique de décomposition n'est pas seulement influencée par le réchauffement climatique; on s'attend égalmeent à ce qu'elle change en fonction de l'altitude, à mesure que le couvert végétal se modifie et migre vers le haut pour suivre les températures optimales sous l'effet du réchauffement. J'utilise donc l'altitude avec des pentes orientées vers le nord et le sud dans les Alpes suisses pour simuler des scénarios climatiques futurs. L'étude des sols à travers le temps et le gradient environnemental pour prédire le changement de SOC est présentée dans les thèmes 1 et 2. L'étude de la dynamique de décomposition en utilisant les gradients d'altitude pour les variations climatiques ainsi que les pentes orientées nord-sud et les sachets de thé est présentée dans les thèmes 3 et 4. En outre, pour approfondir l'étude de l'effet de la pytochimie des organes végétaux sur la dynamique de décomposition, j'ai utilisé des sacs de litière faits à la main et remplis de matériel végétal local pour montrer comment la phytochimie des feuilles et des racines influence la décomposition de la litère dans le cadre d'une expérience de transplantation de litière (thème 3). Enfin, pour examiner le dernier facteur de formation du sol, mais non le moindre, j'ai également étudié la diversité des microarthropodes le long des gradients d'altitude afin de mieux expliquer les indicateurs écologiques locaux de la biodiversité du sol (thème 4). - PublicationAccès libreSolar radiation explains litter degradation along alpine elevation gradients better than other climatic or edaphic parameters(2023-04-27)
; ; Organic matter (OM) decomposition has been shown to vary across ecosystems, suggesting that variation in local ecological conditions influences this process. A better understanding of the ecological factors driving OM decomposition rates will allow to better predict the effect of ecosystem changes on the carbon cycle. While temperature and humidity have been put forward as the main drivers of OM decomposition, the concomitant role of other ecosystem properties, such as soil physicochemical properties, and local microbial communities, remains to be investigated within large-scale ecological gradients. To address this gap, we measured the decomposition of a standardized OM source – green tea and rooibos tea – across 24 sites spread within a full factorial design including elevation and exposition, and across two distinct bioclimatic regions in the Swiss Alps. By analyzing OM decomposition via 19 climatic, edaphic or soil microbial activity-related variables, which strongly varied across sites, we identified solar radiation as the primary source of variation of both green and rooibos teabags decomposition rate. This study thus highlights that while most variables, such as temperature or humidity, as well as soil microbial activity, do impact decomposition process, in combination with the measured pedo-climatic niche, solar radiation, very likely by means of indirect effects, best captures variation in OM degradation. For instance, high solar radiation might favor photodegradation, in turn speeding up the decomposition activity of the local microbial communities. Future work should thus disentangle the synergistic effects of the unique local microbial community and solar radiation on OM decomposition across different habitats. - PublicationAccès libreSoil properties and plant species can predict population size and potential introduction sites of the endangered orchid Cypripedium calceolus(2023-2-16)
; ; Background and Aims To counteract the ongoing worldwide biodiversity loss, conservation actions are required to re-establish populations of threatened species. Two key factors predominantly involved in finding the most suitable habitats for endangered plant species are the surrounding plant community composition and the physicochemical parameters of the soil rooting zone. However, such factors are likely to be context- and species-dependent, so it remains unclear to what extent they influence the performance of target species. Methods We studied large and small Swiss populations of the endangered orchid Cypripedium calceolus. We measured functional traits related to C. calceolus plant and population performance (clonal patch area, plant height, number, of leaf, stems, flowers and fruits), realized vegetation surveys, soil profile analyses, and tested for relationships between plant traits and the surrounding vegetation structure or soil physicochemical parameters. Results Large populations contained bigger patches with more stems and leaves, and produced more flower per individual than small populations. Neither vegetation alliances nor soil classes per se could predict C. calceolus functional traits and population size. However, functional traits explaining population performance and size were related to specific soil parameters (soil organic matter content, pH and phosphorus), in addition to a combination of presence-absence of plant indicator species, relating to ecotones between forests and clearings. Conclusion We show that even for species that can grow across a wide range of vegetation groups both indicator species and specific soil parameters can be used to assess the most favourable sites to implement (re)-introduction actions. - PublicationAccès libreDetecting preservation and reintroduction sitesfor endangered plant species using a two-step modelingand field approach(2022-8-10)
; ; - PublicationAccès libreA standardized morpho-functional classification of the Planet’s humipedons(2022-7-5)
; ; Chersich, SilviaIt was time to take stock. We modified the humipedon classification key published in 2018 to make it easier and more practical. This morpho-functional taxonomy of the topsoil (humipedon) was only available in English; we also translated it into French and Italian. A standardized morphofunctional classification of humipedons (roughly the top 30–40 cm of soil: organic and organomineral surface horizons) would allow for a better understanding of the functioning of the soil ecosystem. This paper provides the founding principles of the classification of humipedon into humus systems and forms. With the recognition of a few diagnostic horizons, all humus systems can be determined. The humus forms that make up these humus systems are revealed by measuring the thicknesses of the diagnostic horizons. In the final part of the article, several figures represent the screenshots of a mobile phone or tablet application that allows for a fast recall of the diagnostic elements of the classification in the field. The article attempts to promote a standardized classification of humipedons for a global and shared management of soil at planet level. - PublicationAccès libreOutils d’évaluation de la diversité et de l’activité des vers de terre : de la science participative à la recherche fondamentale(2022-2-1)
; - PublicationAccès libreEarthworms, Plants, and Soils(New-York: John Wiley and Sons, Inc., 2021)
; ; ; - PublicationAccès libreBioturbation by endogeic earthworms facilitates entomopathogenic nematode movement toward herbivore‑damaged maize roots(2020-12-4)
; ; ; ; Entomopathogenic nematodes (EPNs) have been extensively studied as potential biological control agents against root-feeding crop pests. Maize roots under rootworm attack have been shown to release volatile organic compounds, such as (E)-β-caryophyllene (Eβc) that guide EPNs toward the damaging larvae. As yet, it is unknown how belowground ecosystems engineers, such as earthworms, affect the biological control capacity of EPNs by altering the root Eβc-mediated tritrophic interactions. We here asked whether and how, the presence of endogeic earthworms affects the ability of EPNs to find root-feeding larvae of the beetle Diabrotica balteata. First, we performed a field mesocosm experiment with two diverse cropping systems, and revealed that the presence of earthworms increased the EPN infection potential of larvae near maize roots. Subsequently, using climatecontrolled, olfactometer-based bioassays, we confirmed that EPNs response to Eβc alone (released from dispensers) was two-fold higher in earthworm-worked soil than in earthworm-free soil. Together our results indicate that endogeic earthworms, through burrowing and casting activities, not only change soil properties in a way that improves soil fertility but may also enhance the biocontrol potential of EPNs against root feeding pests. For an ecologically-sound pest reduction in crop fields, we advocate agricultural practices that favour earthworm community structure and diversity. - PublicationAccès libreUse of X-ray microcomputed tomography for characterizing earthworm-derived belowground soil aggregates(2020-3-21)
; ; Turberg, PascalSoil structure is closely linked to biological activities. However, identifying, describing and quantifying soil aggregates remain challenging. X-ray microcomputed tomography (X-ray μCT) provides a detailed view of the physicalstructure at a spatial resolution of a few microns. It could be a useful tool todiscriminate soil aggregates, their origin and their formation processes for a better comprehension of soil structure properties and genesis. Our study aims to (a) determine different X-ray μCT-based aggregate parameters for differentiating earthworm casts belowground (earthworm aggregates) from aggregates that are not formed by earthworms (non-earthworm aggregates), and (b) to evaluate if these parameters can also serve as specific “tomographic signatures” for the studied earthworm species. For this purpose, we set up a microcosm experiment under controlled conditions during 8 weeks, including three species of earthworms tested separately: the epigeic Lumbricus rubellus, the anecic Lumbricus terrestris and the endogeic Allolobophora chlorotica. Our results show that X-ray μCT analysis helps distinguish earthworm aggregates from non-earthworm ones using (a) the relative volume of the components within aggregates and (b) the volumetric mass of aggregates and their global volume. In particular, the volume ratio of mineral grains within the aggregates is significantly different according to earthworm species. So, X-ray μCT is a powerful and promising tool for studying the composition of earthworm casts and their formation. However, future research is needed to take into account the shapes and spatial distribution of the aggregates' components, in particular the different states of organic matter decomposition. - PublicationAccès librePioneer plant Phalaris arundinacea and earthworms promote initial soil structure formation despite strong alluvial dynamics in a semi-controlled field experiment(2019-9-11)
; ; ; Luster, J.Soil structure formation is among the most important processes in river floodplains which are strongly influenced by alluvial dynamics. In the context of river restoration projects, a better understanding of soil structure formation in habitats adjacent to the river can help to prevent damages caused by riverbank erosion. Ecosystem engineers such as pioneer herbaceous plants and earthworms likely contribute to soil structure formation even despite less favourable environmental conditions. This study aims to assess the capacity of the herbaceous perennial and native species Phalaris arundinacea and earthworm communities to promote a stable soil structure in alluvial sediments, in particular fresh alluvial deposits, in the short term. Delimited plots were set-up in a restored floodplain adjacent to the Thur River in NE Switzerland and exposed to natural alluvial dynamics for 19 months. Four treatments were replicated in a randomised complete block design: (i) plots with Phalaris arundinacea as only vegetation, (ii) plots with all vegetation constantly removed, (iii) and (iv) the earthworm community reduced by mustard treatment, otherwise as (i) and (ii), respectively. Soil structure formation was analysed at the end of the experiment using different indicators: aggregate stability, field-saturated hydraulic conductivity and the porosity calculated from X-ray CT reconstructions of freeze cores. Phalaris arundinacea was capable of improving the porosity and aggregate stability of both alluvial sediments present at the beginning of the experiment but also of sediments freshly deposited during the observation period. The latter indicates a structuring effect within only one vegetation period. Earthworm abundance was as a whole very low, most likely due to the large proportion of sand. There was a small earthworm effect on soil structure formation, and only in combination with Phalaris.arundinacea. Our findings highlight the ability of Phalaris arundinacea in efficiently structuring sandy alluvial sediments in the short term even under strong alluvial dynamics. Phalaris arundinacea can therefore play a key role in the early stage of river restoration projects. Thus, facilitating the colonisation by such native pioneer herbaceous plants is a suitable step to improve the success of river restoration projects.