Wiederfund des Elatino alsinastri-Juncetum tenageiae Libb. 1932 in Niedersachsen: Lebensbedingungen, Syndynamik und Schutzbemühungen

Abstract

Täuber, T; Bruns, E.; Steinhoff, K.-J.: Rediscovery of the „Elatino alsinastri-Juncetum tenageiae Libb. 1932 in Lower Saxony – Ecology, syndynamics and conservation efforts. – Hercynia N. F. 40 (2007): 269 –278.After about 18 years two of the rarest plant-species of Lower Saxony – Schoenoplectus supinus and Elatine alsinastrum – were rediscovered in the lowland of the river Seege in the biosphere reserve „Niedersächsische Elbtalaue“. Both species are typical for the Elatino alsinastri-Juncetum tenageiae (Isoëto-Nanojuncetea, Cyperetalia fusci, Elatino-Eleocharition ovatae). In comparison to relevés made in 1988 the current relevés from 2006 differ significantly in species composition. The Soerensen coefficient of similarity based on all species is only 44 %, but 67 % if based on species with more than 40 % constancy. Especially more species with a lower index of moisture (Ellenberg´s indicator values) are part of the plant community now. Fortunately most of the endangered species could be confirmed (e. g. Anagallis minima, Isolepis setacea, Juncus tenageia, Lythrum hyssopifolia). To protect the species and the Elatino alsinastri-Juncetum tenageiae a periodically removal of biomass from the stands of this community is essential. As shown in the past a periodical occurrence of floods in spring regulary or in intervals of about 5 to 20 years is sufficient to reactivate the seed bank of these rare species of Isoëto-Nanojuncetea. There is a clear relation between the occurrence of this plant community and flood levels taken by a nearby detector.