Soil microbial communities exert large influence over plant community structure and dynamics. By altering the soil community in a species-specific manner, plants may differentially impact the fitness of conspecifics and heterospecifics both in time and space. Soil microbially mediated negative feedback on conspecific growth and survival has been found in many systems and is believed to be an important mechanism maintaining plant species diversity. This study explored the generality and magnitude of microbially mediated feedback on plant growth in a tallgrass prairie plant community. We also investigated the relative influence of arbuscular mycorrhizal fungi (AMF), important plant mutualists, on generating feedback on plant growth. Lastly, we explored whether feedback was sufficient to maintain coexistence of plant competitors in our system. 

Results/Conclusions

Microbially mediated feedback on plant growth is common within our system and soil history had plant species-specific effects on growth rates. An important generality was that all plant species did worse when grown in conspecific conditioned soil relative to soil associated with heterospecifics. The trend was reversed when considering only the AMF component of the soil community. Here, plants preferred an AMF community selected for by conspecifics rather than by heterospecific plant species. By taking into account both direct and indirect feedbacks on plant growth we found that microbially mediated feedback can maintain plant diversity within our system. AMF do not appear to be important for supporting plant diversity in this manner. Our results may have implications for maintaining or increasing plant diversity within natural and restored plant communities.