Data from: 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 another’s effect. Additionally, at elevated N, aboveground
herbivory increased the abundance of fungal-feeders relative to
bacterial-feeders, which indicates changes in decomposition pathways
induced by N and herbivory. Belowground herbivory increased the abundance
of omnivorous nematodes. The shifts in both the herbivorous and detrital
parts of the soil food web demonstrate that above- and belowground
herbivory does not only mediate the response of the plant community to N
eutrophication, but in extension also the soil food web sustained by the
plant community. We conclude that feedbacks between effects of above- and
belowground herbivory mediate the response of the grassland ecosystem to N
eutrophication.