Unassisted recovery of plant diversity after reductions in nutrient
inputs can be slow and incomplete. Increased nutrient availability,
light limitation and recruitment limitation are thought to be primary
barriers to diversity recovery. In a full-factorial experiment, we
tested whether removing these obstacles promoted recovery of plant
diversity in a previously cultivated and fertilized old-field. Results
immediately following manipulations demonstrated that these factors
increased diversity to varying degrees, but it was unknown whether these
restorative processes would continue or diminish over time. Here, we
examine long-term responses 13 years after these manipulations and find
that seed addition was the only treatment that continued to increase
plant diversity and productivity. Seed addition also reduced the biomass
of two invasive species that become co-dominant in this grassland after
sufficient nutrient inputs. Our results suggest that alleviating
recruitment limitation can accelerate the recovery of plant diversity,
and ecosystem functions that depend on plant diversity.