Habitat restoration often involves adding seeds of native plant species but it is not well understood what ecological factors influence whether they establish. We studied how multiple plant consumers and habitat edge effects influence plant establishment in recently restored prairies. At Kellogg Biological Station in Western Michigan we applied herbicide to 12 old-field sites and sowed them with native prairie species. To test how edge effects and vertebrate consumers influence sown species establishment we constructed 48 exclosures out of hardware cloth each with a paired pseudoexclosure. Each site had two exclosures near the edge and two in the middle. To test the effects of insects and molluscs we established plots that got treatments of either insecticide, molluscicide, both, or a water control during the growing season. We sampled plant communities in all plots near the end of the 2016-growing season.
We found that excluding mammals and birds increased the number of sown species by 30% with similar effects for edge and center plots. This was likely because of direct consumption of sown seeds or seedlings rather than through changes in non-sown species abundance because we found that the overall community compositions were not different. We also found that plots near the edges of our recently restored prairies had a 40% reduction in sown species richness compared to the middle. This was possibly caused by changes in composition of weedy species, which were quite different between edge and center. Finally, we found that the insecticide and molluscicide treatments did not impact sown species richness. These results suggest that management that suppresses weeds, especially near the edges of sites, and that reduces seed predation by mammals and birds could help increase native plant biodiversity during restoration.