Contrasting effects of land use legacies on grassland restoration in burnt pine plantations

Legacies of previous land use may affect ecosystem recovery after the specific land use has ceased. Determining which legacies do limit ecosystem recovery is critical to perform effective ecological restoration. Pine (Pinus spp.) plantations have replaced various natural habitats including woodlands, shrublands and grasslands worldwide. Following pine tree removal, the restoration of these habitats may be complicated by pine plantation legacies. In this study, we tested three factors that may constrain grassland recovery in a former pine plantation following burning in an inland sand dune region in Hungary. We evaluated the effects of pine litter removal, native grass seeding and the presence of invasive Asclepias syriaca on vegetation composition during seven years of recovery using generalised linear mixed effect models and non-metric multidimensional scaling. We found that litter removal did not facilitate grassland regeneration. Grass seeding led to a fast recovery of grass cover, but negatively affected the abundance of unseeded target species. The presence of Asclepias had only transient effects on seeded grasses but positively affected unseeded target species richness. We conclude that sand grasslands have high restoration potential in burnt pine plantations despite the presence of several land use legacies. We found no evidence that pine litter or the presence of Asclepias would negatively influence grassland recovery, which implies that their removal is not necessary for a successful restoration. We suggest that moderate seeding densities of native grasses need to be applied to avoid the suppression of other target species.