Pedobiologia 49 (2005) 221—228 Abundance and trophic structure of macro- decomposers on alpine pastureland (Central Alps, Tyrol): effects of abandonment of pasturing Julia Seeber a,Ã , G.U.H. Seeber b , Wolfgang Ko ¨ssler a , Reinhard Langel d , Stefan Scheu c , Erwin Meyer a a Department of Terrestrial Ecology and Taxonomy, Institute of Zoology and Limnology, University of Innsbruck, Technikerstr. 25, A-6020 Innsbruck, Austria b Department of Statistics, University of Innsbruck, Universita¨tsstr. 15, A-6020 Innsbruck, Austria c Institute of Zoology, Technische Universita¨t Darmstadt, Schnittspahnstr. 3, D-64287 Darmstadt, Germany d Kompetenzzentrum Stabile Isotope, Forschungszentrum Waldo ¨kosysteme, Universita¨t Go ¨ttingen, Bu ¨sgenweg 1, D-37077 Go ¨ttingen, Germany Received 26 April 2004; accepted 29 October 2004 Summary On four differently managed and abandoned alpine meadows and pastures densities, biomasses and 15 N signatures of the macrofauna were assessed to evaluate the structural and functional changes of the decomposer food webs. The composition of the macrofauna decomposer community changes remarkably after the abandonment of alpine meadows and pastures. Lumbricus rubellus functions as key primary decomposer on alpine meadows and pastures whereas on abandoned sites other primary decomposers including Dendrobaena octaedra, Cylindroiulus meinerti, C. fulviceps and diptera larvae become more important. Decomposer species, such as Enantiulus nanus, presumably function as both primary and secondary decomposers and endogeic earthworms, such as Octolasion lacteum and Aporrectodea rosea, uniformly function as secondary decomposers. Abandonment of pasturing causes a shift in the composition of the macrofauna and the newly established fauna is unable to process and translocate the litter materials produced by the plants of the abondoned sites. & 2005 Elsevier GmbH. All rights reserved. ARTICLE IN PRESS www.elsevier.de/pedobi KEYWORDS Soil fauna; Trophic structure; 15 N; Alpine meadows 0031-4056/$ - see front matter & 2005 Elsevier GmbH. All rights reserved. doi:10.1016/j.pedobi.2004.10.003 Ã Corresponding author. Tel.: +43 512 507 6132; fax: +43 512 507 2930. E-mail address: julia.seeber@uibk.ac.at (J. Seeber).