Testing the usefulness of habitat corridors in mitigating the negative effects of fragmentation:: the soil faunal community as a model system

The corridor hypothesis predicts that habitat corridors should attenuate the negative effects of fragmentation on populations or communities by enhancing the dispersal of organisms between the habitat fragments (the 'rescue effect'). In the present 12-month mesocosm experiment, this hypothesis was tested using the soil micro- and mesofaunal community in humus patches-either connected or unconnected with humus corridors to each other-as a model system. Of particular interest was to explore whether faunal groups with differing life strategies (e.g. in trophic position and dispersal capacity) would differ in their responses to the corridors. The results showed that enchytraeid worms were the only faunal group affected by the corridors: population growth of the worms was promoted by the presence of the corridors. The lack of corridor effects on other soil fauna, such as microarthropods, is likely to be due to unexpected increases in the populations and species richness of this fauna in the humus patches, thus providing no grounds for the rescue effect to operate. The results of the experiment indicate that the faunal groups studied are not sensitive to fragmentation-induced changes in their landscape. It is suggested that the high heterogeneity and availability of resources (including space) even in a small volume of soil render the use of corridors by this soil fauna ineffective. (C) 2003 Elsevier B.V. All rights reserved.