Plant-pollinator interactions represent a crucial ecosystem function that is threatened by anthropogenic landscape alterations. To successfully conserve wild pollinators in degraded landscapes, it is critical that management efforts result in the successful long-term reestablishment of diverse flowering plant communities. Exotic plant invasions represent a major challenge to pollinator habitat restoration and most restoration projects occur over relatively short timelines (less than five years), so long-term evaluations of pollinator habitat enhancement and the effect of exotic plant invasions on pollinator habitat restoration are largely unexplored. To understand exotic plant impacts on pollinator habitat restoration treatments, we characterized floral resource abundance and plant community richness and diversity in 48 prairie restoration plots for 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
Exotic flowering plant species quickly colonized the plots and represented the majority of the floral resources in the early summer. Exotic flowers represented 66% of total flowers produced one year following seeding treatments and as much as 88% by 2015. Only 50% of seeded restoration species were recorded in the plots one year after application, and by 2017 only small suite of restoration plants were represented in the plots. Eight years after initial seeding treatments floral resource abundance in the plots was reduced 4 times 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 plots seeded with high diversity mixes experienced greater exotic plant establishment relative to high diversity 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.