Plant-pollinator interactions represent a crucial ecosystem function that is threatened by anthropogenic landscape alterations. Wild pollinator declines have been recorded in various regions around the world resulting from the use of agricultural chemicals; parasites; diseases; habitat loss, alteration and fragmentation; and invasive species. Habitat alteration and destruction often result in significant reductions of plant abundance, diversity, and population size; and pollinator declines in many habitats have been linked to the loss of diverse floral communities. Therefore, restoring habitat to benefit pollinators is a major conservation concern that depends on the successful long-term reestablishment of diverse floral communities. However, most restoration projects occur over relatively short timelines (less than five years), so the persistence of long-term restoration strategies is largely unexplored. To understand how restoration treatments change over time, we characterized plant community richness and floral resource abundance in 48 prairie restoration plots one and eight years after experimental restoration efforts ceased on a reclaimed strip mine in central OH, USA. Sixteen plots were seeded with a low diversity seed mixture consisting of nine prairie species. The remaining 32 plots were seeded with a high diversity seed mixture that consisted of 20 prairie species considered important resources for pollinators.
Results/Conclusions
One year following seeding treatments floral richness was significantly higher in high compared to low diversity seed mixture plots, but seeding treatment had no effect on floral resource abundance within plots. Only 50% of seeded restoration species were recorded in the plots one year after application, and species from the restoration mixtures only represented 51% of total floral abundance. Exotic flowering plant species quickly colonized the plots and represented 35-40% of the total floral resources one and eight years after seeding application. Eight years after initial seeding treatments floral resource abundance in the plots was reduced by half, relative to year one measurements, and there were no differences in species richness or floral plant abundance in high vs. low diversity plots. Eight year trends also indicated that low diversity plots experienced greater exotic plant establishment relative to high diversity seed mixture plots. Rapid establishment and long-term persistence of exotic plant species suggests that some exotic plants may contribute important floral resources to pollinators in degraded habitats, but this hypothesis requires additional analysis. Low restoration plant recruitment in our plots also suggests that long-term native plant establishment will likely depend on a small suite of highly competitive flowering plants.