The success of ecological restoration of vegetation that involves seed addition is dependent on seedling establishment and performance. The soil legacy of altered microbial community structure left by prior vegetation has been demonstrated to negatively influence seedling performance. Two methods are available to combat the negative effects of soil legacies during restoration. First, identification of plant species that are resistant or non-responsive to soil legacies left by prior vegetation could help increase the success of restoration. Second, soil treatments, such as inoculants of beneficial fungi and bacteria or biocides to decrease the abundance of antagonistic fungi and bacteria, may be applied to remediate microbial soil legacies during restoration.
In the northern Great Plains, restoration of native vegetation is often conducted in areas previously occupied by invasive grasses Bromus inermis and Poa pratensis. Therefore, this project had two aims: to identify native species that may be more resistant to soil legacies left by B. inermis and P. pratensis and to examine the effects of soil treatments (bacterial inoculant, fungal inoculant, fungicide, and a fungicide/bactericide combination) on seedling establishment and performance. A two-phase conditioning and bioassay experiment in environmentally controlled conditions with field-collected soil was performed.
Results/Conclusions
Six native species including cool-season grasses, warm-season grasses, and forbs demonstrated species-specific differences to soil legacies left by the invasive grasses. Native cool-season grass Elymus canadensis and native forb Echinacea angustifolia were not significantly impacted by soil legacies of B. inermis nor P. pratensis and therefore may be strong candidates for restoration. However, native warm-season grass Schizachyrium scoparium was the most negatively impacted by soil legacies and might not be a strong candidate for restoration when soil legacies are anticipated. Soil fungicide did increase the seedling performance of S. scoparium in soil with a P. pratensis legacy but not in the B. inermis legacy soil. Overall, none of the soil treatments improved the performance of all native species in the legacy soil. The implication of this project are that identification of species less responsive to legacies left by invasive species (such as E. canadensis and E. angustifolia) may be more useful to restoration than microbial inoculants or biocides for restoration for grasslands in the northern Great Plains.