P scaber, 2006, Photo: Katy Juhaszova
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Soil invertebrates are known to greatly influence the rate and pathways of microbial decomposition. We are looking at how native and non-native soil invertebrates affect decomposition and nutrient cycling in anthropogenic environments. We are focusing on species level processes instead of the traditional functional groupings, because different species have different natural histories. In addition to gaining insight into the functioning of urban soil communities, such studies also address “redundancy” in soil communities; a fundamental question in ecology and conservation biology.
We have measured potential N-mineralization and nitrification rates in the presence of earthworms (three species one native and two introduced) and terrestrial isopods (six species, all introduced). In the earthworm study the Asian Amynthas hilgendorfi had the largest impact on N-cycling processes, while there was no difference between the native Eisenoides loennbergi and the European Lumbricus terrestris. In contrast, incubation experiments with six terrestrial isopod species resulted in net immobilization (Figure 1.). The overall effect was the same, but the rates were different among the species. Our results point to strong species effects, which have to be taken into account when different microhabitats are invaded by different species.
Figure 1. Potential N mineralization rates of soil in the presence (blue colors) and absence (brown) of six terrestrial isopod species.
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