Rare wetland grass Coleanthus subtilis in Central and Western Europe – current distribution, habitat types, and threats

Abstract

The moss grass Coleanthus subtilis (Tratt.) Seidl is a rare, diminutive grass which grows on wet muddy bottoms of drained water bodies displaying a high degree of water level dynamics, such as fishponds or water reservoirs. Due to the temporal character of its habitat, C. subtilis has a very short life cycle of only a few weeks. Therefore, the species and its habitats are legally protected on both national and international levels. This paper focuses on habitats and the conservation of C. subtilis in Central and Western Europe. For the period of 2000–2013, the Czech Republic with more than 200 sites represents the main distribution area of this species in Central and Western Europe. During the same period, C. subtilis was recorded from 45 sites in three regions of Germany (33 Lusatia, 11 Ore Mountains, 1 Mid-Elbe River), 16 sites in France, 13 sites in Poland, and four sites in Austria. Since 2000, the number of records within these seven regions seems to have followed different trends: whereas two regions (Lusatia, Germany and southern Poland) became newly colonized and many populations established, in one region (Ore Mountains, Germany) the number of records diminished. Owing to its specific life cycle, both reproduction success and maintenance of C. subtilis populations are closely linked to the prevailing water level regime, mainly dependent on the management of the water body. Management for the conservation of C. subtilis populations should consider the entire complex of water bodies, as well as individual ponds. For the preservation of the species, at least one pond in each complex should be drained every year and each pond should be drained at least once within 5 years. Depending on local climatic conditions, ponds should be drained for 8–10 weeks during the time period from mid-March to mid-November.

Keywords

• EU Habitats Directive
• fishponds
• Isoëto-Nanojuncetea
• management
• species protection
• temporary wetland vegetation