Is the protection of habitat directive Eleocharis carniolica in its northern limits really needed? – A life strategy based investigation

Eleocharis carniolica is included in the EU Habitat Directive and legally protected in many European countries. It is also considered as one of the most threatened plants in Poland. It typically occurs in muddy habitats, wet meadows, lake or pond shores or temporary puddles, but in Poland this species usually occurs at disturbed anthropogenic sites such as road verges or drainage ditches. Despite being the focus of a number of ecological and conservation studies, E. carniolica still does not have a fully recognized ecology and life-strategy, particularly with regard to breaking seed dormancy and germination. To find out the population performance and species propagation potential in Poland, we have conducted experiments aimed at assessing the seed germination conditions and efficiency. The main goal was to discover the crucial factors that stimulate germination. The results of the experiments suggest that light is a pivotal factor for triggering germination of E. carniolica seeds. Moreover, E. carniolica’s seed bank consisted of about 80 % dormant seeds. The only effective method for dormancy breaking was warm stratification (placing the seeds at high temperature on a moist substrate) with application of gibberellic acid (GA₃)_, and even a few days of warm stratification resulted in effectively overcoming dormancy. Eleocharis carniolica's germination features are typical for plants adapted to frequent disturbances with a short life expectancy and large reproductive effort. Our results strongly suggest that E. carniolica has a ruderal life strategy at its northern distribution limits and probably can be considered as an alien species in Poland.