Exotic plant invaders alter ecosystem process rates compared to natives, but the extent to which this is driven by (1) higher productivity, (2) trait differences compared to native plants, or (3) novel biotic interactions in recipient communities, remains unknown. We created plant communities varying in exotic dominance, plant traits, soil organisms and invertebrate herbivores and measured ecosystem C and N cycling effects.
Results/Conclusions
Biotic interactions with both soil organisms and herbivores were the strongest drivers of exotic effects on ecosystem functions, particularly measures of carbon loss from communities. Exotic traits, but not biomass, drove intermediate functions that explained how biotic interactions with invaders increased carbon losses. These results suggest that differences in the way soil microbes and herbivores respond to particular traits of exotic plants can explain the heightened rates of ecosystem cycling in invaded systems.