The Survival of Transplants of Rare Ligularia sibirica is Enhanced by Neighbouring Plants

Reintroduction programs are often initiated to restore the viability of endangered plant populations, whose decline is usually caused by loss of suitable habitats. Ligularia sibirica is a species associated with wetlands. It is endangered in Europe and has declined considerably in Estonia since the cessation of traditional management and, in addition, drainage leading to the overgrowth of habitats. The purpose of this work was to estimate the extent of the impact of competition from neighbouring plants and habitat change caused by overgrowing on the survival of transplants of L. sibirica and thereby assess the effectiveness of reinforcement. Laboratory-grown transplants were planted back into their original populations in plots arranged in a two × two (vegetation intact or removed × open or overgrown habitat) factorial experimental design, and their survival was followed for three years. The survival differed notably among populations, but the percentage of surviving plants per plot was on average higher in plots with intact vegetation and in open habitats. The latter indicates that overgrowing indeed decreases habitat quality for this species, despite the fact that plants of L. sibirica can often be found in forested habitats. The lower survival in plots where vegetation had been removed can largely be explained by increased damage caused by animals. In intact plots, by contrast, neighbouring plants provide shelter and protection. Our results stress the importance of restoration and preservation of habitat quality for the protection of this rare species, for which reinforcement may be effective.