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Negative plant–soil feedbacks dominate seedling competitive interactions of North American successional grassland species

Authors


Abstract

Question

Seed-transmitted fungal endophytes of grasses can influence competitive interactions via direct effects of infection on host plant performance or via indirect effects, such as plant–soil feedback effects that operate through changes to soil properties. To date, however, these direct and feedback effects have been evaluated separately. What is the relative importance of endophyte infection vs endophyte-mediated plant–soil feedback effects on competition between seedlings of the grass tall fescue (Schedonorus phoenix) and common species of American Midwestern old-field successional grasslands?

Location

Long-term field experimental plots at the Indiana University Research and Teaching Preserve and greenhouse of Indiana University (Bloomington, IN, USA).

Methods

Endophyte-free (E-) and endophyte-infected (E+) tall fescue seedlings were grown individually and in intraspecific competition and pair-wise interspecific competition. Endophyte-mediated plant–soil feedback effects were incorporated by growing seedlings in soil conditioned by either E– or E+ tall fescue.

Results

We found that E– and E+ tall fescue experienced stronger intra- and interspecific competition when competing in self-conditioned soils. This pattern was consistent regardless of competitor identity.

Conclusions

Our findings suggest that the direct benefits of endophyte infection do not drive competitive responses of tall fescue at the early stages of plant development, at least under the conditions examined in our study. Rather, negative plant–soil feedbacks may be more important in moderating plant responses to competitive interactions during seedling establishment of this species. Explicit manipulation of factors such as herbivory and abiotic stress is an important future direction for studies evaluating the relative importance of endophyte infection vs soil-mediated endophyte effects on host plant performance.

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