Shannon, Sarah , Firestone, Jeffrey .
Is the allelopathy observed in Eastern Deciduous Forest invasive shrubs an artifact of experimental design, a familiar weapon, or a mechanism of invasion?
Several invasive plant species have allelopathic effects on native species in bioassays - inhibiting germination, growth, or fecundity. However, recent studies have suggested that soil's biotic and abiotic properties can reduce the impact of allelopathic chemicals. In addition, while some invasive species show allelopathic potential, their effects have not been compared to the allelopathic potential of co-occurring native species. If an invasive species has the same allelopathic effects as a pre-existing native species, these allelopathic effects are unlikely to be a mechanism of invasion. We tested the allelopathic potential of three invasive shrubs of the Eastern Deciduous Forest (Elaeagnus umbellata, Lonicera maackii, and Ligustrum sp.) and three co-occurring woody natives (Lindera benzoin, Cercis canadensis, and Acer saccharum) on the germination, survival, and growth of twelve species (the six woody species listed above and six native herbaceous species). These species were tested in sterilized soil and soil containing an Eastern Deciduous Forest soil microbial community to determine the relative impact of the soil microbial community. This formed a full factorial design of leachate from 6 woody species tested on 12 seed species in the 2 soil treatments (the presence and absence of soil microbes; n=1,440). We found that the presence of a live soil microbial community significantly altered the effects of the six leachates on germination, survival, and growth. While most of the six leachate species exhibited some allelopathic potential in either live or sterile soil on at least one of the seed species, no one species consistently inhibited all species' germination, survival, or growth. Ligustrum had the most consistent inhibition of seed germination in live soil, but did not significantly impact other growth stages. Additionally, the invasive shrubs were not inherently more allelopathic than the native species. The significance of the soil microbial community treatment shows that soil microbes should be taken into account in allelopathy bioassays. Our results suggest that dominance by any one of the woody species can affect the germination, survival and growth of seedlings under its canopy, but that this is not unique to invasive plants.
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1 - Indiana University, Department of Biology, 1001 East Third Street, Jordan Hall 142, Bloomington, IN, 47405, USA
soil microbial community
Presentation Type: Oral Paper:Papers for Sections
Date: Monday, July 9th, 2012
Time: 10:15 AM