Effects of small-scale habitat fragmentation, habitat corridors and mainland dispersal on soil decomposer organisms

Habitat corridors have been suggested to be one possible way to reduce the often negative effects of habitat fragmentation. In the present experiment, we focused on small habitat fragments (humus patches) inhabited by soil decomposer organisms. These fragments were either unconnected or connected with each other by habitat (humus) corridors. Moreover, these systems were either isolated from the mainland by a dispersal barrier (plastic “walls”) or were open to dispersal from the mainland. The fragments and corridors were embedded in a matrix of mineral soil that was expected to be uninhabitable or at least an unpreferred habitat for the organisms studied. Undisturbed forest soil functioned as the mainland. The results showed that habitat fragmentation decreased the abundance of microarthropods (Acari). Presence of corridors affected positively the abundance of mites, but only after the first 4 months of the experiment: later on, this effect disappeared. Furthermore, this “corridor rescue effect” was only seen in the systems isolated from the mainland, whereas in the open systems, dispersal from the mainland apparently overwhelmed the effect of corridors. Also soil fungi benefited from the corridors. The results indicate that soil decomposer organisms, microarthropods in particular, may be useful as model organisms in studies focusing on the ecological consequences of habitat fragmentation. It is also suggested that connecting otherwise isolated small habitat fragments with each other by habitat corridors may increase the persistence time of fragment-inhabiting populations.