Experimental ecology and habitat specificity of the endangered plant Apium repens (Jacq.) Lag. at the northern edge of its range

Abstract

Background: Successful conservation of endangered species such as Apium repens requires sound information about their ecology and habitat demands. Currently, knowledge about this species is very limited.

Aims: Our objectives were to analyse the ecology and habitat demands of A. repens to achieve a better understanding of the factors relevant for its conservation.

Methods: We set up a transplantation trial and conducted experiments on competitive ability and inundation tolerance of A. repens; these were complemented by an analysis of 85 vegetation relevés and land use and soil analyses of 24 north German populations.

Results: Both intra- and interspecific competition had negative impacts on the growth of A. repens. Disturbance alleviated the impact of competition. Apium repens tolerated fresh water inundation of up to 56 days; salt water inundation proved to be fatal. Transplantation showed that seedlings are suitable founder propagules for reintroduction schemes and that disturbance is vital for their prospering.

Conclusions: Apium repens is a light-demanding weak competitor that is dependent on disturbances and well-adapted to ground-water fluctuations and inundation. We recommend that disturbance regimes and hydrological conditions of extant populations should be maintained and suggest seedling-based reintroductions as a valuable tool for conserving the species.

Keywords:

• Apium repens
• competitive ability
• conservation
• grazing
• Habitats Directive
• indicator values
• rare plant

Acknowledgements

We thank the State Agency for Nature and Environment Schleswig-Holstein (LANU) for allowing us to collect A. repens seeds on Fehmarn and the farmers and landowners for allowing us to work on their land. Klaus Jödicke, Andreas Mohr, Joachim Stuhr, Ulrich Voigtländer, Jennifer Wimmer and Walter Wimmer carried out the monitoring of north German A. repens populations (the latter two acting on behalf of the Lower Saxony Water Management, Coastal Defence and Nature Conservation Agency, NLWKN) and kindly provided the respective data. The analytic laboratory of the Institute of Soil Science at the University of Hamburg is gratefully acknowledged for carrying out the soil chemistry analyses. Lutz Eckstein provided valuable comments that improved the quality of the manuscript. This research was funded by the EU-LIFE project Rehabilitation of the Baltic Coastal Lagoon Habitat Complex (BaltCoast, LIFE05NAT/D/000152).