Multiple components of global change, including changes in land-use, can affect the composition and function of soil microbial communities. It is possible that these changes in soil microbial communities can affect plant community composition either through direct effects of soil microbes on plants or through changes in plant-soil feedbacks. In two experiments, we tested these possibilities by measuring the strength of plant-soil feedback in remnant and restored tallgrass prairies. One tested feedback responses of individual plant species, and the other tested feedback responses in community mesocosms. We also measured plant functional traits and mycorrhizal responsiveness, and tested these traits as predictors of establishment limitation in restored tallgrass prairies.
In our two plant-soil feedback experiments, we observed strong plant-soil feedback effects, but these effects did not differ between remnant and restored prairies. However, we did observe significant main-effects of the soil from different sites on the growth of individual plant seedlings and on the composition of plant community mesocosms. Additionally, we found that plant species with traits associated with a late-successional life-history and species that are highly responsive to mutualisms with mycorrhizal fungi were the most likely to experience strong establishment limitation in ecological restoration. Overall, our results find strong effects of plant-soil feedbacks on plant and soil communities, and restoration practitioners may be able to choose plant species for restoration that will create favorable soil conditions, including promoting microbial mutualists. However, these plant-soil feedbacks do not appear to overcome long-lasting legacy effects of past soil disturbances. Consequently, reintroduction of key components of the soil microbial community may be needed, especially when restoration goals include the re-establishment of late-successional plant communities. We are currently analyzing the composition of mycorrhizal fungi communities at sites representing a range of land-use histories to identify taxa that are resilient to anthropogenic disturbance and those that may require active reintroduction in ecological restoration.