Top-Down Cascade Effects of the Long-Clawed Shrew (Sorex unguiculatus) on the Soil Invertebrate Community in a Cool-Temperate Forest
2016
Namba, Tomoyuki | Ohdachi, Satoshi D.
In a soil ecosystem, bottom-up control is generally considered more influential than topdown control, although some empirical studies have suggested that predators have a trophic cascade effect on soil animals at lower trophic levels. In the present study, the effects of the long-clawed shrew, a mammalian predator at a high trophic level, on the soil invertebrate community and litter decomposition were investigated in a field experiment using enclosures. In the presence of the shrew, the population densities of earthworms, isopods and spiders tended to decrease, whereas that of large springtails and centipedes appeared to increase. This result might have been caused by the shrew's direct predation on the former invertebrates and the release from predation by spiders on springtails. The reason of the increase of centipedes was unknown. Shrew had no effects on litter decomposition rates both by litter trap analysis and litter-bag test. The top-down effects of shrews on litter decomposition might have been diluted through a complex food-web and the observing period of the present study might be too short to detect litter decomposition process. Experiment for longer time might demonstrate more explicit effect of the shrew on the soil ecosystem.
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