THE IMPORTANCE OF SOIL MICROORGANISMS FOR MAINTAINING DIVERSE PLANT COMMUNITIES IN TALLGRASS PRAIRIE

Premise of the study: According to the Janzen-Connell hypothesis, soil microorganisms have the potential to increase plant community diversity by mediating negative feedback on plant growth. Evidence for such microbe-driven negative feedback has been found in a variety of terrestrial systems. However, it is currently unknown how general this phenomenon is within most plant communities. Also unknown is the role of mutualists in generating such feedback: do they decrease the influence of soil-mediated negative feedback on plant fitness or do they increase its effect by proliferating with plant hosts to which they give the least benefit? Methods: We investigated soil-microbe-mediated feedback via a series of reciprocal transplant experiments in the greenhouse using soil from a restored tallgrass prairie and native tallgrass prairie plant species. Key results: We found that negative feedback was very common but that mutualists (arbuscular mycorrhizal fungi) influence plant growth in opposition to the overall negative feedback trend. Conclusions: Widespread microbially mediated negative feedback indicates that plant community diversity and composition in tallgrass prairie are dependent on soil microorganisms. Native soil microorganisms should be considered in restoration efforts of tallgrass prairie and, potentially, other native plant communities.