Alien Invasive Plant Effect on Soil Fauna Is Habitat Dependent

Abstract

Invasive alien plants often modify the structure of native plant communities, but their potential impact on soil communities is far less studied. In this study, we looked at the impact of invasive Asian knotweed (Reynoutria spp.) on two major soil mesofauna (Collembola) and microfauna (Nematodes) communities. We expected ingress of knotweed to differentially affect faunal groups depending on their trophic position, with the lower trophic levels being more impacted than the higher trophic groups according to the closer relationship to plants for basal trophic groups. Furthermore, we expected the knotweed impact to depend on habitat type (forest vs. meadow) with more pronounced changes in abundances of soil invertebrate in invaded meadows. Plant and soil invertebrates were sampled in six sites (three forest and three meadows) in northern France in both control and invaded plots. Our results showed that the presence of knotweed strongly reduced native plant species’ diversity and abundance. Soil fauna also responded to the invasion by Asian knotweed with different responses, as hypothesized, according to trophic position or life-forms. Furthermore, abundances of several collembolan life-forms were influenced by the interaction between the factors “Habitat” and “Knotweed”. This may explain the difficulty to easily generalize and predict the consequences of plant invasion on belowground diversity, although this is of crucial importance for alleviating negative consequences and costs of biological invasion.