Above- and belowground insect herbivores mediate the impact of nitrogen eutrophication on the soil food web in a grassland ecosystem

Insect herbivores are important drivers of ecosystem processes in grasslands, and can mediate the grassland’s response to environmental change. For example, recent evidence shows that above- and belowground herbivory, individually and in combination, can modify how a plant community responds to nitrogen (N) eutrophication, an important driver of global change. However, knowledge about how such effects extend to the associated soil food web is lacking. In a mesocosm experiment, we investigated how communities of soil nematodes – an abundant and functionally important group of soil organisms – responded to above- and belowground insect herbivory at contrasting N levels. We found that the strongest influence of above- and belowground herbivory on the nematode community appeared at elevated N. The abundance of root-feeding nematodes increased when either above- or belowground insect herbivores were present at elevated N, but when applied together the two herbivore types cancelled out one an...