Colonization behaviour of Collembola under different conditions of dispersal

In soil dumps of the opencast mine site Berzdorf near Gorlitz (Eastern Germany), different kinds of colonization behaviour of Collembola have been observed. In immigration test plots, exposed on a nearly vegetation free dump site between May 1997 and September 1998, 17 species of Collembola were proved to have been transported by air. The first immigrant was Bourletiella pistillum. After 4 months, stable populations were established by Mesaphorura florae and Parisotoma notabilis. The open area around the test plots was inhabited by 20 species of epedaphic Collembola. From these, only 6 species were found in the immigration test plots. The fauna was caught in drift-protected and normal pitfall traps. Nearly 80% of the individuals profited from wind drifting. Of these, Bourletiella pistillum and Isotoma viridis were dominant. Lepidocyrtus cyaneus, L. paradoxus, Orchesella cincta and O. villosa were mainly caught in protected pitfall traps. Thus, their main means of dispersal might be through active locomotion. Subterranean immigration to litter-filled minicontainers was tested in two 45-year-old afforested dump sites by successively checking the minicontainers in 6-week intervals from October 1997 to January 1999. Altogether, 26 species of Collembola invaded the minicontainers. Some species found in the humus layer only in recedent frequencies reached considerably higher dominances in the minicontainers 30 weeks after their installation: Folsomia candida even colonized minicontainers closed by gauze of 20-mum mesh size at high densities. Mesaphorura tenuisensillata, Protaphorura meridiata, and Proisotoma minuta occurred preferentially in minicontainers with larger mesh-sizes. Biological and methodical conclusions from the observations are discussed.