Document: VIC-3-40-51

Mycorrhizal fungi influence plant community composition by changing competitive hierarchies.

ALLISON, V.J* and T.KRAJANIEMI

University of Michigan, Ann Arbor MI 48105, USA 1

Abstract:
Mycorrhizal fungi may potentially alter plant community composition by influencing individual performance or species interactions. Using an experimental null model approach, we tested the hypothesis that mycorrhizal fungi change community composition by their differential impact on plant species competitive abilities. To test this hypothesis, cover of seven old-field perennial species in null plots was compared to mixed plots, and the impact of the fungicide benomyl, fertilizer, and both fertilizer and fungicide assessed. After two growing seasons, we found a significant four way interaction between species, competition, fungicide and fertilizer (p<0.0103). The competitive hierarchy changed in response to fungicide, and the magnitude of response was influenced by fertilizer. We conclude that mycorrhizal fungi can influence community composition by changing competitive hierarchies. Further, several species were advantaged by fungicide under non-competitive but not competitive conditions, suggesting the relative cost to benefit of mycorrhizal fungi is in part dependent on species interactions.

Keywords: mycorrhizas, competitive hierarchies, plant community composition

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This abstract is being presented at: 3:30 PM in session:
MYCORRHIZAL FUNGI