Das Hechtenloch auf dem Weg zur Pfeifengraswiese
Krüsi, B.O. (2012). Das Hechtenloch auf dem Weg zur Pfeifengraswiese. Mitteilungen der Naturforschenden Gesellschaft in Bern, Neue Folge, 69, 93-115. Peer reviewed.; ;
The «Hechtenloch» on the way to a Molinion-type fen
The «Hechtenloch» is an old bend of the River «Aare», between Thun and Berne. Until 2005, the area was used for agriculture and heavily fertilized. During the winter of 2009/10 the «Aaretal Foundation» had removed 30 cm of topsoil in order to eliminate most of the nutrients. Material from a newly created pond was used for establishing the optimal distance between soil surface and groundwater table needed for the development of the envisaged Molinion-type fen already present in the adjacent «Riedli». On nearly 50% of the area the groundwater table is now 50 cm beneath the soil surface.
In order to monitor the development of the vegetation, a monitoring concept
was designed. In 2011, 50 permanent plots, each 1m x 1m in size, were marked with the help of magnets, and vegetation relevés were made both in spring and autumn.
Two years after topsoil removal already 163 vascular plant species were found
on the restoration area, including nine Red List species (Switzerland), three target species and two rare pioneer species. Half of the plant species are typical for ruderal and half-ruderal areas. However, also three invasive alien species of the Black List were already present. In autumn 2011, on the 50 permanent plots the vegetation covered on average already 34%. The weighted average indicator values indicated, despite removal of the topsoil, ample amounts of plant-available nutrients, moderate water supply, favourable light conditions and poor aeration of the soil.
The colonization of the newly created area is well under way. Future surveys
will reveal how quickly and by which successional pathways the vegetation will
develop and whether or not it goes towards the desired fen meadow (Molinion).
To prevent the encroachment of woody species and/or invasive neophytes, the
restoration area will be mowed at least once a year. In addition, the establishment of particularly valuable species is fostered by dispersing seeds collected in the adjacent fen «Riedli».