Prairie restorations involve converting post-agricultural land to support the flora of native prairies. Prairie restorations, however, are challenging because many farmlands have legacies of elevated soil phosphorus due to past fertilizer use, as well as differences in their soil microbiomes relative to untilled native prairies. These factors may disrupt beneficial plant-microbe interactions. We asked how prairie legumes (plants that use nitrogen fixed by microbes) are affected by soil microbes and fertilizer. In the greenhouse, we grew 10 legume and 10 non-legume species in soil from remnant (undisturbed) and restored prairies with and without added phosphorus. We predicted that all species would have greater biomass in remnant soil if beneficial native soil microbes were present, and that legumes might be more affected than non-legumes. In addition, we predicted that fertilizer inputs would not be as beneficial for species grown in restored soils since elevated phosphorus may further disrupt plant-microbe interactions.
Results/Conclusions
We found that remnant prairie microbes increased the growth of half of the legume species while the non-legumes were unaffected, suggesting that legumes may be more sensitive than non-legumes to the loss of beneficial native soil microbial communities. We did not detect widespread interactive effects of phosphorus and soil origin, suggesting that positive effects of microbes are not consistently disrupted by phosphorus; However, legume and non-legume species varied widely in their responses. These results suggest that the roles of soil microbes and phosphorus in shaping prairie restoration may be more complex and dependent on species identity. The microbial community of post-agricultural land may not be optimal for prairie plants with unique microbial needs; additions of native microbes should be considered during prairie restorations.