Impact of elevated atmospheric CO2 concentration on soil microbial biomass and activity in a complex, weedy field model ecosystem

Authors

  • Christian Kampichler,

    1. Institute of Zoology, University of Vienna, Althanstraße 14, A-1090 Wien, Austria, and GSF National Research Centre for Environment and Health, Institute of Soil Ecology, Ingolstädter Landstraße 1, D-85764 Neuherberg, Germany,
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  • Ellen Kandeler,

    1. Federal Agency and Research Centre for Agriculture, Institute of Soil Management, Spargelfeldstraße 191, A-1226 Wien, Austria,
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  • Richard D. Bardgett,

    1. School of Biological Sciences, 3.614 Stopford Building, University of Manchester, Oxford Road, Manchester M13 9PT, UK,
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  • T. Hefin Jones,

    1. NERC Centre for Population Biology, Imperial College at Silwood Park, Ascot Berkshire SL5 7PY, UK
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  • Lindsey J. Thompson

    1. NERC Centre for Population Biology, Imperial College at Silwood Park, Ascot Berkshire SL5 7PY, UK
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Christian Kampichler, GSF – National Research Centre for Environment and Health, Institute of Soil Ecology, Ingolstädter Landstraße 1, D-85764 Neuherberg, Germany, fax + 49/89-31873376, e-mail kampichl@gsf.de

Abstract

Although soil organisms play an essential role in the cycling of elements in terrestrial ecosystems, little is known of the impact of increasing atmospheric CO2 concentrations on soil microbial processes. We determined microbial biomass and activity in the soil of multitrophic model ecosystems housed in the Ecotron (NERC Centre for Population Biology, Ascot, UK) under two atmospheric CO2 concentrations (ambient vs. ambient + 200 ppm). The model communities consist of four annual plant species which naturally co-occur in weedy fields and disturbed ground throughout southern England, together with their herbivores, parasitoids and soil biota. At the end of two experimental runs lasting 9 and 4.5 months, respectively, root dry weight and quality showed contradictory responses to elevated CO2 concentrations, probably as a consequence of the different time-periods (and hence number of plant generations) in the two experiments. Despite significant root responses no differences in microbial biomass could be detected. Effects of CO2 concentration on microbial activity were also negligible. Specific enzymes (protease and xylanase) showed a significant decrease in activity in one of the experimental runs. This could be related to the higher C:N ratio of root tissue. We compare the results with data from the literature and conclude that the response of complex communities cannot be predicted on the basis of oversimplified experimental set-ups.

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