Changes in the soil detrital food chain associated with Gunnera tinctoria invasions. Soil 16S rRNA

Whilst invasive plants can modify community and ecosystem attributes, there islittle information on their impact at different trophic levels. Here, we examined the effects ofGunnera tinctoria on the soil detrital food chain, the major pathway for energy flow interrestrial ecosystems and the recycling of nutrients. Measurements of the natural abundancesof C and N isotopes, and assessments of soil microbial populations show that G. tinctoriadrives the soil food web and that C is rapidly transferred from decomposing litter to wormpopulations. Based on the C isotope compositions of plant material and detritivorous worms(i.e., earthworms and enchytraeid worms), all worms contribute to G. tinctoria litterdecomposition, irrespective of their feeding preference. The increased role of largerearthworms in litter decomposition was also associated with changes in the soil microbialcommunity, with some bacterial genera absent from invaded areas. Of particular interest wasa three-fold increase in Nitrospira spp. in invaded areas, likely due to an increase inearthworm-related ammonia production, with this being rapidly converted to nitrate. Giventhe poor representation of other ammonia and nitrite oxidizing soil bacteria, many of theNitrospira spp. present in invaded soils may perform complete ammonia oxidation (i.e.,COMAMMOX). Our results indicate a greater role of earthworms in decompositionprocesses in areas invaded by G. tinctoria, resulting in modifications in the other soil biotaand an increase in soil nitrate.