Incorporating microbes into plant community ecology
McCormick, Melissa , Szlavecz, Katalin , Whigham, Dennis .
Alteration of microbial communities by non-native earthworms.
Non-native species can dramatically alter the availability of nutrients and the microbial community, including alteration of mycorrhizal networks that are essential for efficient resource acquisition by most plant species. We used field manipulations to determine the effects of non-native earthworms on mycorrhizal fungi and tree seedling growth. We manipulated earthworm density and leaf litter in plots into which seedlings of two arbuscular (AM; Liriodendron tulipifera and Acer rubrum) and two ectomycorrhizal (ECM; Quercus rubra and Fagus grandifolia) trees were planted. We measured enzyme activity, microbial abundance and composition in the plots as well as seedling growth and mycorrhizal colonization. In a second experiment we separately manipulated hyphal disruption, soil mixing, and soil fertility, in addition to adding non-native earthworms, to determine how different earthworm activities affected mycorrhizal fungi. In both experiments we used taxon-specific quantitative PCR to measure the abundance of bacteria, fungi, AM and ECM in the soil. We combined these analyses with assessment of enzyme activity to separate direct and indirect effects of non-native earthworms on seedling growth and survival.
ECM and AM fungi were less abundant in plots with more earthworms and results of the second experiment suggested that earthworms primarily affected mycorrhizae through soil mixing. Both mycorrhizal groups were also more abundant in mature compared to successional forests. ECM seedlings were smaller in high density earthworm plots, while the reverse was true for AM seedlings but effects depended on forest land-use history. Earthworm biomass was consistently higher in plots with tulip poplar litter than those with beech litter, suggesting earthworm invasion may have changed feedbacks between the plant and microbial communities. In these experiments we found that earthworm-driven alterations in the microbial community, especially effects on the mycorrhizal community, directly affected the plant community, while plant effects on the microbial community were also mediated by earthworms.
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1 - Smithsonian Institution, Smithsonian Environmental Research Center, 647 Contees Wharf Rd., Edgewater, MD, 21037, USA
2 - The Johns Hopkins University, Dept. of Earth and Planetary Sciences, 3400 N. Charles St., Baltimore, MD, 21216, USA
Presentation Type: Symposium or Colloquium Presentation
Location: Westminster Room/Chase Park Plaza
Date: Monday, July 11th, 2011
Time: 10:45 AM