PS 12-168 - Dual inoculation of rhizobia and AMF synergistically improve growth of mid and late successional legumes in a restored prairie

Abstract: North American native prairies used to cover much of the Midwest and the Great Plains, but about 96% of this ecosystem has been lost. Efforts have been made to restore these ecosystems, but restoration often comes as a challenge. Prairie restoration usually involves planting or sowing native prairie plants into post-agricultural fields, but added species do not always establish. Legumes are a diverse group of plants which include native prairie species that often fail to establish and are critical to prairie ecosystems. We hypothesize this is due to changes in the microbial communities with which legumes have mutualistic relationships: rhizobia and arbuscular mycorrhizal fungi (AMF). Additionally, we hypothesize late successional legumes rely on these multi-mutualistic relationships for establishment and growth more than early successional legumes, and would respond synergistically to rhizobia and AMF treatments. To test this, we inoculated seedlings of eight native perennial legumes with varying life histories with rhizobia and/or AMF and transplanted them into a restored prairie. We measured legume height and scored health (greeness) over one growing season. At the end of the growing season we harvested the above ground biomass of the surviving legumes.

Rhizobia inoculation increased seedling survival regardless of successional status, while AMF and dual inoculation appeared to have no effect. Dual inoculation had a positive synergistic effect on seedling scored health. We found that rhizobia and AMF did not independently increase legume biomass or height with the exception of one late successional legume that increased in both biomass and height when inoculated with rhizobia. Dual inoculation did increase biomass and height synergistically in mid and late successional legumes. However, the magnitude of the synergistic response did not increase with plant successional status in either biomass or height. Synergistic effects vary from study to study, and our research further strengthens the importance of understanding community interactions for restoration success. Due to the importance of legumes and diversity to prairie ecosystems, the interactions of legumes and microbial communities should be at the forefront of prairie restoration research and efforts.