Consistent effects of a non-native earthworm on soil microbial communities in three subtropical forests

Non-native earthworms have increasingly become a global problem due to the strong effects they exert on biodiversity and ecosystem functions in their introduced habitat. Quantifying interactions between non-native earthworm and microbial communities in forest ecosystems should increase our understanding of non-native earthworm-induced changes in soil biogeochemical cycles and plant diversity. In a microcosm experiment, we investigated non-native earthworm-microbial interactions in soils originating from three typical subtropical forests in which pan-tropical non-native Pontoscolex corethrurus (Muller, 1857) was the dominant earthworm. Our study showed that P. corethrurus strongly affected the soil microbial communities in all three soils. The cast production and burrowing activities of P. corethrurus significantly reduced total soil microbial biomass and soil bacterial biomass, but did not change soil fungal biomass. As a consequence, P. corethrurus substantially increased the ratio of fungi to bacteria. For most soil microbial properties, these effects occurred in all three soils, i.e., they were independent of habitat type. Furthermore, the microbial communities in the three forest soils were found to be more similar with than without P. corethrurus. These results suggest that P. corethrurus can greatly affect soil microbial communities in a variety of habitats where the earthworm has been introduced. Our results also showed that microbial biomass was substantially higher in the P. corethrurus gut than in the surrounding soil and that new habitat types can modify the microbial community in the gut of P. corethrurus.