1) Universität Essen, Abteilung Hydrobiologie, Essen, Germany;
2) Universität Hannnover, Institut für Landschaftspflege und Naturschutz, Hannover, Germany;
3) Hochschule Vechta, Institut für Naturschutz und Umweltbildung, Vechta, Germany

Review Study on Near-natural Conditions
of Cetral European Mountain Streams,
With Particular Reference to Debris and Beaver Dams:
Results of the "REG Meeting" 2000

DANIEL HERING ¹⁾, MARC GERHARD ²⁾, ELLEN KIEL ³⁾, THOMAS EHLERT ¹⁾ & TANJA POTTGIESSER¹⁾

With 5 Tables

Key words: Debris dams, beaver dams, Castor fiber, Central Europe, reference conditions, potentially natural conditions, stream morphology

Abstract

This paper summarises the results of the "Rhitron Ecology Group" meeting in Essen (March 2000), supplemented by a literature evaluation.
  An extended view of small mountain streams in Central Europe under "potentially natural conditions" is presented. We focus on the potential impact of natural transverse structures (debris dams and beaver dams) on stream morphology, hydrology, habitat composition and communities. Furthermore, impact of other stream mophological features, which are presently lacking in the Central European landscape, is described.
  We suggest that Central European mountain streams are characterised by a higher proportion of lentic zones under "potentially natural conditions". Morphological degradation leads to a loss of lentic zones and to an increase of current velocities and coressponding changes in faunal composition, particularly higher abundance and proportion of reophilic species and a decrease of species preferring lentic zones. This should be regarded in future stream assessment.