Effects of global warming on Antarctic soil microorganisms and associated functions

E. Yergeau

    Research output: PhD ThesisPhD thesis

    Abstract

    Summary
    Soil microorganisms are involved in all the major global biogeochemical cycles, but
    consequences of ongoing climate changes on these organisms and associated functions are
    mostly unknown. Antarctic terrestrial habitats are ideal testing grounds for the impacts of
    perturbation on soil microbes, and the ecosystem functions for which they are responsible.
    Indeed, the unusually harsh environmental conditions of terrestrial Antarctic habitats result
    in ecosystems with simplified trophic structures, where microbial processes are especially
    dominant as drivers of soil-borne nutrient cycling. The Antarctic Peninsula is one of the
    most rapidly warming regions in the world, yet few studies have addressed the potential
    impacts of global warming on soil microbes and associated nutrient-cycling functions
    inhabiting these simple and vulnerable environments.
    The main objective of this thesis is to assess the effects of global warming on Antarctic
    soil-borne microorganisms and associated functions. This objective was pursued via three
    complementary experimental approaches:
    1. A detailed description of the microbial communities, and their associated functions,
    inhabiting Antarctic terrestrial habitats along a latitudinal transect, as a proxy for longterm,
    large-scale climatic changes (Chapters 2–5).
    2. A study of the short-term responses of soil microorganisms and associated functions to
    increasing temperature and altered freeze-thaw cycle frequency in controlled
    microcosm experiments (Chapter 6).
    3. An assessment of the responses of soil microbial communities and functions in a field
    manipulation experiment involving three years of artificial enhancement of soil
    temperature warming using open-top chambers at three field locations (Chapter 7).
    Such an integrated approach is thought to help overcome methodological, spatial and
    temporal limitations and to help discriminate between general and context-dependant
    responses of ecosystems to global warming.
    Results from the latitudinal gradient studies revealed that the large differences in climatic
    conditions at the different sites sampled exerted strong influence on microbial community
    structure, diversity, abundance and functions. In addition, vegetation cover was observed to
    also exert a strong effect, indicating that indirect effects of global warming through
    vegetation expansion may lead to large ecosystem responses. Microcosm studies
    highlighted that fungi and bacteria respond differently to increasing temperature and
    changes in freeze-thaw cycle frequency. These experiments also showed that several
    functional genes involved in the N-cycle were more sensitive to changes in freeze-thaw
    cycle frequency than to increases in temperature. Field warming experiments showed that
    the short-term responses of soil organisms and associated functions to warming of a few
    degrees were highly dependent on local environmental condition. Large responses were
    only recorded in moist, nutrient-rich Antarctic environments, while few responses were
    observed in nutrient- or water-limited environments and the more temperate soils.
    Taken together, the results presented in this thesis suggest that global warming will have
    profound effects on Antarctic soil microorganisms and associated functions. The short-term
    effects will be highly variable and shaped by local environmental conditions, while in the
    longer-term, global warming will strongly affect soil microorganisms and nutrient-cycling
    functions, both directly and indirectly.
    Original languageEnglish
    QualificationDoctor (dr.)
    Awarding Institution
    • VU University Amsterdam
    Supervisors/Advisors
    • Kowalchuk, G.A., Promotor
    • Aerts, M.A.P.A., Promotor
    Award date30 Jun 2008
    Place of PublicationAmsterdam
    Publisher
    Publication statusPublished - 30 Jun 2008

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