13.2.2012: Forschung CH

Lebensraum Gletschervorfeld im Wandel der Zeit

Les marges proglaciaires au fil du temps


Jürg Schlegel und Matthias Riesen

Es bestehen nur rudimentäre Kenntnisse über die faunistische Besiedlung von Gletschervorfeldern. Die Resultate des Forschungsprojektes «Gletschervorfeld Morteratsch» der Fachstelle Umweltplanung der ZHAW Wädenswil illustrieren die Bedeutung des Alters der Eisfreiheit für die Raumnutzung von Laufkäfern. Artenzahlen und Bestandesdichten der Laufkäfer steigen in den ersten 40 Jahren Eisfreiheit kontinuierlich an und erreichen nach einem Rückgang (bei 50 bis 90 Jahren Eisfreiheit) einen zweiten Höhepunkt.

Nos connaissances sur la colonisation faunistique des marges proglaciaires sont rudimentaires. Les résultats du projet de recherche «marges proglaciaires Morteratsch» de la Fachstelle Umweltplanung de la ZHAW Wädenswil illustrent l’importance de la durée libre en glace pour l’utilisation du terrain par les carabes. Le nombre d’espèces et la densité de peuplement des carabes augmentent continuellement au cours des 40 premières années libérées des glaces et atteignent après un recul (vers 50 à 90 années libre en glace) un deuxième pic.


Accelerated by global warming, retreating glaciers leave behind spatially ordered moraines with underlying primary succession and disturbance. Current knowledge of primary succession comes mainly from studies of vegetation dynamics. Information about aboveground macroinvertebrates is still scarce. We used carabid beetles (Coleoptera; Carabidae) as indicator taxon to assess the effects of (1) terrain age (species turnover along the proglacial chronosequence) and (2) small-scale habitat architecture (vegetation cover, surface texture) on the carabid assembly. For this purpose, 33 sampling sites with pitfall traps were installed throughout the glacier foreland Morteratsch (Engadine, Switzerland), adjacent sparse forests serving as reference sites. With a total of 33 carabid species on the foreland and another 2 on the reference sites, the study area yielded a very high carabid species diversity compared to other glacier forelands. In general, the age of deglaciation proved to be a highly significant predictor for the carabid distribution, especially for particularly discriminant species. Observed species richness and activity densities showed bimodal patterns with a steep increase within the first ca. 40 years, a decline between around 40–90 years, and a further increase towards the terminal moraine. There was no evidence of dispersal-stochasticity: distinct clusters of sites with similar species composition were found. Microhabitat suitability proved to be a secondary effect, embedded in a temporal framework of primary succession. Surface cover with litter, herbs and dwarf-shrubs turned out to be the crucial habitat factors.

Keywords:
Gletschervorland, Wirbellose, Sukzession, Klimawandel

Art der Publikation:
Fachpublikation

Literatur:
Schlegel J., Riesen M. (in press*). Environmental gradients and succession patterns of carabid beetles (Coleoptera: Carabidae) in an Alpine glacier retreat zone. Journal of Insect Conservation, Springer, 19 pages. *published online 30/11/2011
http://www.springerlink.com/content/h4xk83r177826821/

Kontaktadresse:
Jürg Schlegel
Zürcher Hochschule für Angewandte Wissenschaften ZHAW
Institut für Umwelt und Natürliche Ressourcen
Grüental, Postfach
CH-8820 Wädenswil

juerg.schlegel@zhaw.ch
Tel: +41 (0)58 934 58 67


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