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Howard, Justin [1], Edwards, Jackson [2], Lubin, Terra [3], Bever, James D [3], Byers, Diane [4].

Does the invisible belowground determine the visible aboveground: Prairie plant species' responses to plant-soil microbial interactions.

The tallgrass prairie ecosystem of North America is known for its extraordinary species diversity, particularly in eastern regions that have greater precipitation, which has been proposed to determine this diversity. An alternative (or complementary) hypothesis proposes interactions between long-lived prairie plants and the microbial community developed in their rhizosphere promotes species diversity. Specifically, the buildup of species-specific pathogens would result in lowering the vigor of the plant (and competitive ability) and lowering the quality of the soil patch for their offspring (negative plant soil feedback or negative PSF). Thus, negative PSFs are expected to promote species diversity. However, plant-soil microbial interactions can also result in the buildup of microbial species (mycorrhizae fungi and  Rhizobium  bacterial) with more mutualistic interactions resulting in greater vigor of the plant (positive PSF), which would promote success of specific species. If the species receiving positive PSF are not the competitive dominant species of the community, positive PSF may retain specific species, also increasing the community diversity. To test the extent and type of PSF in the tallgrass prairie, we set up a series of experimental field plots with different prairie plant species where each plot was "trained" with a specific plant species and all plants were grown with native tallgrass prairie soil inoculum before being transplanted to the experimental plots. The following year we grew the same species of plants in greenhouse experiments using the experimentally trained soil as an inoculum in a factorial design enabling testing for both positive and negative PSF. This study is part of a larger REU project which will enable assessment of positive and negative PSF across a geographic and environmental gradient (Illinois to Kansas). We will be focusing on the responses of plants to our PSF plots' inoculum in Illinois. We predicted that plants would have lower fitness (estimated by biomass) when grown in their own species inoculum compared to other species (negative PSF).    Prairie species included were a grass (Andropogon gerardii), two legumes (Lespedeza capitata,  Dalea purpurea) and two forbs (Lobelia spicata,  Silphium integrifolium). We found root or shoot biomass was increased by the legumes when treated either with their own species soil or the other legume's soil as an inoculum which would be a positive PSF. Currently, we have not found evidence for any significant negative PSF. Belowground dynamics resulting in negative or positive PSF are key for understanding aboveground dynamics in natural and reconstructed prairies.

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1 - Illinois State University, School of Biological Sciences, Campus 4120, Normal, IL, 61790, USA
2 - Illinois State University, School of Biological Sciences, Campus Box 4120, Normal, IL, 61790, USA
3 - University of Kansas, Ecology and Evolutionary Biology, 2101 Constant Ave, Lawrence, KS, 66047, USA
4 - Illinois State University, School Of Biological Sciences, Campus Box 4120, Normal, IL, 61790, United States

plant-soil interactions
plant-fungal interactions
plant-microbe interactions
plant-soil feedbacks.

Presentation Type: Oral Paper
Session: ECO8, Ecology: Interactions
Location: /
Date: Friday, July 23rd, 2021
Time: 10:00 AM(EDT)
Number: ECO8001
Abstract ID:929
Candidate for Awards:None

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