The role of seed rain, seed bank, and clonal growth in plant colonization of ancient and restored grasslands

Understanding the establishment of plant species is important to inform management of restored grasslands and to preserve biodiversity in ancient grasslands. In grassland communities, plant species can establish from seeds arriving via spatial dispersal, from seeds in the soil seed bank or through vegetative spread from nearby source individuals. However, this colonization potential and the likelihood of species establishment can vary in grasslands with different land-use history. We investigated the relative importance of local species recruitment sources, such as dispersal in space and time and species presence in adjacent grasslands, in determining establishment of plant species in eight grasslands with different land-use history (paired ancient grasslands continuously managed as pasture vs. restored grasslands on former forest). At each grassland, we established plots (0.25 m2) to monitor seedling emergence from seed dispersal, seed bank, and recorded clonal growth over two growing periods. We found that the likelihood of species establishment was highest from local seed rain, and that species present in the local species pool were more able to germinate and establish in both type of grasslands. Species from the seed bank and clonal growth contributed to a lesser extent to species establishment, but represented a greater proportion of the recolonization and regeneration of species in ancient grasslands. These results demonstrate that surrounding grasslands serve as a source for colonizing species and that dispersal from the adjacent grasslands is the key process in regeneration and colonization of plants. These results imply that the recovery of grasslands depends heavily upon to links to species source in grasslands, especially in restored grasslands. Therefore, management plans should incorporate rotational livestock grazing and larger networks of grassland in restoration efforts, which will enable to desirable species to establish and persist in grasslands. In our experiment we followed the assembly of the species over 2 years on different grassland types (ancient continuously managed vs. restored grasslands) with special focus on the origin of the species. We found that that the colonizing species are spatially dispersed and established from local species pools. Species from the seed bank mostly recruited in continuously managed grasslands rather than the restored grassland.image