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Community diversity and invasion resistance: An experimental test in a grassland ecosystem and a review of comparable studies

Authors

  • Andy Hector,

    Corresponding author
    1. NERC Center for Population Biology, Imperial College at Silwood Park, Ascot, Berks UK-SL5 7 PY, United Kingdom,
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  • Kim Dobson,

    1. NERC Center for Population Biology, Imperial College at Silwood Park, Ascot, Berks UK-SL5 7 PY, United Kingdom,
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  • Asher Minns,

    1. NERC Center for Population Biology, Imperial College at Silwood Park, Ascot, Berks UK-SL5 7 PY, United Kingdom,
    2. Environmental Change Institute, University of Oxford, Oxford UK-OX1 3UB, United Kingdom and
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  • Ellen Bazeley-White,

    1. NERC Center for Population Biology, Imperial College at Silwood Park, Ascot, Berks UK-SL5 7 PY, United Kingdom,
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  • John Hartley Lawton

    1. NERC Center for Population Biology, Imperial College at Silwood Park, Ascot, Berks UK-SL5 7 PY, United Kingdom,
    2. Natural Environmental Research Council, Polaris House, Swindon UK-SN2 1EU, United Kingdom
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*Author to whom correspondence should be addressed. Email: a.hector01@ic.ac.uk

Abstract

The relationship between community diversity and invasion resistance in a grassland was examined using experimental plant assemblages that varied in species richness and composition. The assemblages were weeded for three seasons to remove unsown species and we used the number of weeded seedlings, their total biomass and the number of species removed as indicators of community resistance and susceptibility to invasion. In general, we found a positive relationship between invasion resistance and increasing community diversity. Similar patterns of establishment were observed at the end of the fourth field season after several months without weeding. Increased invasion resistance with higher diversity appears to come through reduced levels of several above- and belowground resources, although these did not fully explain the effects of species richness in the study’s analyses. Experimental increases and reductions of litter biomass within the study’s experimental plant assemblages did not modify these patterns significantly. A review of comparable studies of invasion across directly manipulated diversity gradients revealed similar patterns. Positive effects of species diversity on invasion resistance were found in experimental manipulations of plant diversity conducted in the field and in the glasshouse, from studies with aquatic microcosms and in a marine system. Although some exceptions to this pattern were found in both terrestrial plant systems and aquatic microcosms, it was concluded that in biodiversity manipulation experiments more diverse communities are generally more resistant to invasion.

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