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Mitchell, Edward

Nom
Mitchell, Edward
Affiliation principale
Site web
Fonction
Professeur ordinaire
Email
edward.mitchell@unine.ch
Identifiants
https://libra.unine.ch/handle/123456789/357
_
0000-0003-0358-506X

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  • Publication
    Accès libre
    Comparative ecology of vascular plant, bryophyte and testate amoeba communities in four Sphagnum peatlands along an altitudinal gradient in Switzerland
    (2015-3-4)
    Koenig, Isabelle 
    ;
    Feldmeyer-Christe, Elizabeth
    ;
    Mitchell, Edward 
    Monitoring tools are needed to assess changes in peatland biotic communities and ecosystem functions inresponse to on-going climate and other environmental changes. Although the responses of soil organismsand plants to ecological gradients and perturbations do not always correlate, peatland monitoring ismainly based on vegetation surveys. Testate amoebae, a group of protists, are important contributorsto carbon and nitrogen cycling in organic soils and are useful bioindicators in peatland ecology andpaleoecology. There is however little comparative data on the value of testate amoebae, vascular plantsand bryophytes as bioindicators of micro-environmental gradients in peatlands.We compared the relationships of testate amoebae, bryophytes, and vascular plants with soil tempera-ture, water table depth, micro-habitats and the carbon and nitrogen content of Sphagnum mosses in fourpeatlands along a 1300 m altitudinal gradient in Switzerland. We used the full diversity of vascular plantsand bryophyte but only a selection of ten easily identifiable testate amoeba morpho-taxa (i.e. species orspecies-complexes).Indirect and direct gradient ordinations, multiple factor analysis (MFA) and transfer function modelsfor inferring water table depth showed that a selection of ten testate amoeba taxa are more powerful (%variance explained in RDA) and accurate (discrimination among habitats) indicators of local conditions(micro-habitat type, water table depth and Sphagnum C/N ratio) than the vegetation (vascular plants andbryophytes either individually or combined and considering the full diversity).Our study showed that a limited list of ten easily identifiable testate amoeba taxa have higher bioindi-cation value than the full bryophytes and vascular plants. Furthermore, testate amoebae can be analyzedon samples collected at any season (accessibility allowing and if precise sampling sites are well marked)– a clear advantage for biomonitoring and can be used to infer past changes from the peat record at thesame taxonomic resolution. This simple approach could therefore be very useful for biomonitoring ofpeatlands.
  • Publication
    Accès libre
    Comparative ecology of vascular plant, bryophyte and testate amoeba communities in four Sphagnum peatlands along an altitudinal gradient in Switzerland
    Koenig, Isabelle 
    ;
    Feldmeyer-Christe, Elizabeth
    ;
    Mitchell, Edward 
    Monitoring tools are needed to assess changes in peatland biotic communities and ecosystem functions in response to on-going climate and other environmental changes. Although the responses of soil organisms and plants to ecological gradients and perturbations do not always correlate, peatland monitoring is mainly based on vegetation surveys. Testate amoebae, a group of protists, are important contributors to carbon and nitrogen cycling in organic soils and are useful bioindicators in peatland ecology and paleoecology. There is however little comparative data on the value of testate amoebae, vascular plants and bryophytes as bioindicators of micro-environmental gradients in peatlands.
    We compared the relationships of testate amoebae, bryophytes, and vascular plants with soil temperature, water table depth, micro-habitats and the carbon and nitrogen content of Sphagnum mosses in four peatlands along a 1300 m altitudinal gradient in Switzerland. We used the full diversity of vascular plants and bryophyte but only a selection of ten easily identifiable testate amoeba morpho-taxa (i.e. species or species-complexes).
    Indirect and direct gradient ordinations, multiple factor analysis (MFA) and transfer function models for inferring water table depth showed that a selection of ten testate amoeba taxa are more powerful (% variance explained in RDA) and accurate (discrimination among habitats) indicators of local conditions (micro-habitat type, water table depth and Sphagnum C/N ratio) than the vegetation (vascular plants and bryophytes either individually or combined and considering the full diversity).
    Our study showed that a limited list of ten easily identifiable testate amoeba taxa have higher bioindication value than the full bryophytes and vascular plants. Furthermore, testate amoebae can be analyzed on samples collected at any season (accessibility allowing and if precise sampling sites are well marked) – a clear advantage for biomonitoring and can be used to infer past changes from the peat record at the same taxonomic resolution. This simple approach could therefore be very useful for biomonitoring of peatlands.
  • Publication
    Accès libre
    The performance of single- and multi-proxy transfer functions (testate amoebae, bryophytes, vascular plants) for reconstructing mire surface wetness and pH
    Mitchell, Edward 
    ;
    Payne, Richard J.
    ;
    van der Knaap, Willem O.
    ;
    Lamentowicz, Łukasz
    ;
    Gąbka, Maciej
    ;
    Lamentowicz, Mariusz
    Peatlands are widely exploited archives of paleoenvironmental change. We developed and compared multiple transfer functions to infer peatland depth to the water table (DWT) and pH based on testate amoeba (percentages, or presence/absence), bryophyte presence/absence, and vascular plant presence/absence data from sub-alpine peatlands in the SE Swiss Alps in order to 1) compare the performance of single-proxy vs. multi-proxy models and 2) assess the performance of presence/absence models. Bootstrapping cross-validation showing the best performing single-proxy transfer functions for both DWT and pH were those based on bryophytes. The best performing transfer functions overall for DWT were those based on combined testate amoebae percentages, bryophytes and vascular plants; and, for pH, those based on testate amoebae and bryophytes. The comparison of DWT and pH inferred from testate amoeba percentages and presence/absence data showed similar general patterns but differences in the magnitude and timing of some shifts. These results show new directions for paleoenvironmental research, 1) suggesting that it is possible to build good-performing transfer functions using presence/absence data, although with some loss of accuracy, and 2) supporting the idea that multi-proxy inference models may improve paleoecological reconstruction. The performance of multi-proxy and single-proxy transfer functions should be further compared in paleoecological data.