Increased N deposition can cause critical transitions in grasslands that result in lasting declines in biodiversity and shifts in community composition. The mechanisms preventing the recovery of biodiversity following cessation of N addition are not well understood. We examined long-term responses of productivity and species richness to restoration treatments in a grassland that had experienced N fertilization and cessation. The treatments consisted of a full-factorial combination of organic carbon addition, litter removal, and seed addition. We sampled percent cover and aboveground biomass data 1 year and 10 years following the intervention. Results from the first year of the experiment were previously reported. Here we report new results after resampling a decade later.
Results/Conclusions
One year after the intervention, seed addition and litter removal increased species richness. The combination of litter removal and seed addition produced the greatest increase in species richness. Ten years later, seed addition was the only treatment to significantly increase the species richness, inverse Simpson’s Diversity and biomass production. Also, seed addition reduced the proportional biomass of two invasive species, E. repens and P. pratensis, that become co-dominant after sufficient N inputs. Other treatments did not have a significant effect on productivity or biodiversity. Treatment combinations with seed addition all increased productivity and species richness, however, seed addition alone had the greatest effect. These results indicate that dispersal or recruitment limitation could be an important factor preventing recovery of biodiversity after cessation of N addition.