Disturbance and biomass removal enhance population reinforcement of a plant species of European conservation concern

ABSTRACT Background Arnica montana is a threatened plant species that highly depends on species-specific conservation action. Aims We conducted three experiments in montane heathlands to quantify the role of disturbance for population reinforcement of A. montana. Methods In the first experiment, clusters of A. montana were raked to remove biomass and promote vegetative growth. In two other experiments, we analysed what kind of disturbance intensity is necessary to promote the establishment of A. montana by seeding and planting, respectively. Different traits with respect to population structure and growth of A. montana (e.g. abundance of rosettes and flowering stems) were measured. Results Raking resulted in the removal of bryophytes and parts of the herb layer and strongly fostered vegetative reproduction of A. montana. In general, disturbance enhanced the establishment of A. montana by seeding, however, the establishment rate was low. By contrast, planting of A. montana in plots whose surface was disturbed greatly increased the populations of A. montana. Conclusion Our study highlights that populations of A. montana much depend for reproduction on the disturbance of the above-ground vegetation. We identified (i) disturbance of vegetation within existing populations for fostering vegetative reproduction and (ii) planting of A. montana in previously disturbed vegetation as the most suitable measures for reinforcing populations of this species of European conservation concern.