Biotic and Abiotic Effects of Remnant and Restoration Soils on the Performance of Tallgrass Prairie Species

Interactions between plants and soil microbes are increasingly recognized as an important component in the functioning of ecosystems. Because these interactions affect and are affected by soil abiotic conditions, restoration efforts must consider the interactions between the plant community, the soil community, and the soil abiotic conditions. We sampled soil from 20 independently restored tallgrass prairies and 8 natural prairie remnants in southern Manitoba. Soils from the restored sites had 4.5 times higher phosphate levels than soils from the remnants. In whole soil assays, big bluestem (Andropogon gerardii) and Culver's root (Veronicastrum virginicum) had significantly greater growth in soil from the remnant sites. A second growth assay using sterile and inoculated soil from a subset of these sites showed that while big bluestem benefited from soil biota on both remnants and restored sites, the effect was twice as strong on the remnant sites. Our results suggest that plants on restored prairies are less reliant on soil microbes due to the higher fertility found within their soils. Our data suggests that like other ecosystems, residual high fertility in tallgrass prairies may facilitate invasion by non-native plants.