Evaluating Native Plant Community Characteristics After Restoration Efforts in Invaded Tallgrass Prairies

Abstract

Invasive grasses reduce native plant diversity in North America's tallgrass prairies and are commonly controlled using herbicide followed by seeding of native plants. Despite the long-term development of plant communities after seeding, evaluations of restoration outcomes rarely exceed 2 yr. Further, plant community development may be influenced by grazing by domestic cattle, a dominant land use in working landscapes that typify the Great Plains, yet this relationship is seldom explored. In the eastern Great Plains, we evaluated plant community characteristics over 8 yr in tallgrass prairies invaded by tall fescue (Schedonorus arundinaceus) after treatment with herbicide followed by seeding native plants. We compared 16 restoration sites seeded once between spring 2014 and 2021 to 2 unrestored, invaded sites and 3 high-diversity reference sites that were not restored. Domestic cattle grazed six restoration sites and one unrestored, invaded site; the remaining sites were ungrazed. In July 2021, we quantified the dominance and cover of herbaceous plants and the composition and richness of seeded species. Annual forb dominance, seeded species establishment and composition, native forb cover, and seeded species richness of older restorations closely resembled references. However, grazed restorations resembled high-quality references less closely than ungrazed restorations. Future studies should consider identifying high-quality reference sites that are grazed because ungrazed references may represent inappropriate target conditions for grazed restorations. The similarities we observed between older restorations and references highlight the importance of long-term evaluations when quantifying restoration outcomes and indicate that treatment with herbicide followed by native seeding has long-lasting positive effects for restoring native plant communities in invaded tallgrass prairies. Enhancing the practicality and effectiveness of restoration efforts in working landscapes is key to supporting grassland restoration.