Mccormick, Melissa , Szlavecz, Katalin , Xia, Lijun , Saunders, Jaclyn K. , Morcol, Taylan , Whigham, Dennis .
Effects of non-native earthworms on soil microbes and tree seedling growth.
Invasions by non-native earthworms are of concern worldwide, yet few studies have addressed how non-native earthworms might affect plant growth, especially tree recruitment. We used a series of field manipulations to test mechanisms by which earthworms can affect mycorrhizal fungi and so, indirectly, tree seedling growth. We manipulated earthworm density and litter composition in field enclosures in forests with different land use histories and examined responses in enzyme activity, microbial abundance and composition, and tree seedling growth. We also established 6-week mesocosms in two forests in which we separately manipulated hyphal disruption, soil mixing, and soil fertility, in addition to adding non-native earthworms, to determine which earthworm activities affected mycorrhizal fungi the most. We used taxon-specific quantitative PCR to measure microbial abundance in the soil and analyzed soil enzyme activity to separate direct and indirect effects of non-native earthworms on seedling growth and survival.
Earthworm abundance, leaf litter species, and land use history all affected the abundance of different microbial taxa in field enclosures. Red oak seedlings, which are ectomycorrhizal, grew less well in tulip poplar than in beech litter in field enclosures with, but not without, earthworms. Red maple, and tulip poplar seedlings grew equally well in both litter types, regardless of whether earthworms were abundant. Q-PCR in field mesocosms showed that bacteria and ectomycorrhizal fungi (Russulaceae and Tomentella), though not total fungi, decreased in response to disruption, suggesting a possible explanation for the decreased growth of oak seedlings. β-glucosidase and polyphenol oxidase responded positively to mixing and disruption, while N-acetyl-glucosaminidase and polyphenol oxidase increased in response to fertilization with earthworm casts, suggesting different aspects of earthworm activity affected different microbial functions. These results suggest that non-native earthworms can have significant effects on soil microbial communities, soil enzymatic activity, and tree seedling growth and that land use history plays an important role in determining what those effects will be.
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website of earthworm-mycorrhizae project
1 - Smithsonian Environmental Research Center, P.O. Box 28, 647 Contees Wharf Rd., Edgewater, MD, 21037, USA
2 - Johns Hopkins University, Dept. of Earth and Planetary Sciences, Baltimore, MD, 21218, USA
3 - University of Washington, School of Oceanography, Box 357940, Seattle, WA, 98195-7940, USA
4 - Smithsonian Environmental Research Center, P.O. Box 28, Edgewater, MD, 21037, USA
Presentation Type: Oral Paper:Papers for Sections
Location: 552A/Convention Center
Date: Monday, August 2nd, 2010
Time: 4:30 PM