Quantifying direct and indirect effects of fungicide on an old-field plant community: an experimental null-community approach |
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Authors: | Victoria J Allison Tara K Rajaniemi Deborah E Goldberg and Donald R Zak |
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Institution: | (1) Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI 48109-1048, USA;(2) School of Natural Resources and Environment, University of Michigan, Ann Arbor, MI 48109-1115, USA;(3) Landcare Research, PO Box 40, Lincoln, 7640, New Zealand;(4) Present address: Department of Biology, University of Massachusetts Dartmouth, North Dartmouth, MA 02747-2300, USA |
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Abstract: | Environmental perturbations can alter the composition of plant communities, either directly, by altering growth of some species
more than others, or indirectly, by altering the strength of interspecific interactions among species. The relative importance
of direct and indirect effects is not at all well known. We used an experimental approach to quantifying direct and indirect
effects of fungicide on the composition of a plant community. To separate the direct and indirect impacts of fungicide we
grew plant species in monoculture and mixed communities, and with and without the systemic fungicide benomyl. We predicted
that direct effects of fungicide would be important at low but not high nutrient availability, while indirect effects would
be more important at high nutrient availability. After 3 years there was little impact of fungicide on arbuscular mycorrhizal
fungal colonization, and on soil microbial community composition assessed as the relative abundance of different phospholipid
fatty acids. Like fertilizer, fungicide increased plant biomass. However, in contrast to fertilizer, this did not result in
a decline in species evenness. Although not significant, the direct effects of fungicide tended to oppose the indirect effects
of both fungicide and interspecific interactions on plant community composition. Experiments relying on fungicide treatments
must be interpreted extremely cautiously, because the impact of fungicide is potentially the integrated response of plants
to multiple factors, including arbuscular mycorrhizal fungi, pathogenic and saprophytic fungi, and nutrient inputs. |
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Keywords: | Combined monocultures design Fertilizer Fungicide Interspecific interactions AMF |
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