M. A. Bradford,^1* T. H. Jones,² R. D. Bardgett,³ H. I. J. Black,⁴ B. Boag,⁵ M. Bonkowski,⁶ R. Cook,⁷ T. Eggers,¹ A. C. Gange,⁸ S. J. Grayston,⁹ E. Kandeler,¹⁰ A. E. McCaig,¹¹ J. E. Newington,¹ J. I. Prosser,¹¹ H. Setälä,¹² P. L. Staddon,¹³ G. M. Tordoff,¹ D. Tscherko,¹⁰ J. H. Lawton¹¹⁴

Human impacts, including global change, may alter the composition of soil faunal communities, but consequences for ecosystem functioning are poorly understood. We constructed model grassland systems in the Ecotron controlled environment facility and manipulated soil community composition through assemblages of different animal body sizes. Plant community composition, microbial and root biomass, decomposition rate, and mycorrhizal colonization were all markedly affected. However, two key ecosystem processes, aboveground net primary productivity and net ecosystem productivity, were surprisingly resistant to these changes. We hypothesize that positive and negative faunal-mediated effects in soil communities cancel each other out, causing no net ecosystem effects.

¹ Natural Environment Research Council Centre for Population Biology, Department of Biological Sciences, Imperial College at Silwood Park, Ascot, SL5 7PY, UK.
² Biodiversity and Ecological Processes Research Group, Cardiff School of Biosciences, Cardiff University, Post Office Box 915, Cardiff, CF10 3TL, UK.
³ Department of Biological Sciences, Institute of Environmental and Natural Sciences, Lancaster University, Lancaster, LA1 4YQ, UK.
⁴ Centre for Ecology and Hydrology, Merlewood, Grange-over-Sands, LA11 6JU, UK.
⁵ Scottish Crop Research Institute, Invergowrie, Dundee, DD2 5DA, UK.
⁶ Technische Universität Darmstadt, Fachbereich 10, Biologie, D-64287 Darmstadt, Germany.
⁷ Institute of Grassland and Environmental Research, Plas Gogerddan, Aberystwyth, SY23 3EB, UK.
⁸ School of Biological Sciences, Royal Holloway, University of London, Egham, TW20 0EX, UK.
⁹ Macaulay Land Use Research Institute, Craigiebuckler, Aberdeen, AB15 8QH, UK.
¹⁰ Institute of Soil Science, University of Hohenheim, 70599 Stuttgart, Germany.
¹¹ Department of Molecular and Cell Biology, University of Aberdeen, Institute of Medical Sciences, Foresterhill, Aberdeen, AB25 2ZD, UK.
¹² Department of Ecological and Environmental Sciences, University of Helsinki, Niemenkatu 73, FIN-15140 Lahti, Finland.
¹³ Department of Biology, University of York, Post Office Box 373, York, YO10 5YW, UK.
¹⁴ Natural Environment Research Council, Polaris House, North Star Avenue, Swindon, SN2 1EU, UK.
^*   To whom correspondence should be addressed. E-mail: m.a.bradford{at}ic.ac.uk

   Present address: Engineering and Physical Sciences Research Council, Polaris House, North Star Avenue, Swindon, SN2 1ET, UK.

   Present address: Plant Research Department, Risø National Laboratory, Postbox 49, Roskilde, DK-4000, Denmark.