• grassland;
  • invasive;
  • mean C;
  • phenology;
  • succession;
  • tallgrass

Restored grasslands comprise an ever-increasing proportion of grasslands in North America and elsewhere. However, floristic studies of restored grasslands indicate that our ability to restore plant communities is limited. Our goal was to assess the effectiveness of restoration seeding for recovery of key plant community components on former exotic, cool-season pastures using a chronosequence of six restoration sites and three nearby remnant tallgrass prairie sites in West-Central Iowa. We assessed trends in Simpson's diversity and evenness, richness and abundance of selected native and exotic plant guilds, and mean coefficient of conservatism (mean C). Simpson's diversity and evenness and perennial invasive species abundance all declined with restoration site age. As a group, restoration sites had greater richness of native C3 species with late phenology, but lower richness and abundance of species with early phenology relative to remnant sites. Total native richness, total native abundance (cover), mean C, and abundance of late phenology C3 plants were similar between restoration and remnant sites. Observed declines in diversity and evenness with restoration age reflect increases in C4 grass abundance rather than absolute decreases in the abundance of perennial C3 species. In contrast to other studies, restoration seeding appears to have led to successful establishment of tallgrass prairie species that were likely to be included in seeding mixtures. While several floristic measures indicate convergence of restoration and remnant sites, biodiversity may be further enhanced by including early phenology species in seeding mixes in proportion to their abundance on remnant prairies.