Timing of simulated aboveground herbivory influences population dynamics of root-feeding nematodes

Aims Plant damage inflicted by aboveground herbivores can occur at different stages of plant development and can induce plant responses that affect the growth of belowground herbivores. This study explores impacts of aboveground herbivory at different plant development stages on the population dynamics of root-feeding nematodes. Methods We simulated aboveground herbivory by clipping the foliage of the grass species Holcus lanatus, and tested how plant defoliation at different times (1, 4 or 7 weeks after nematode inoculation) influenced the population of two root-feeding nematode species: the endoparasitic Pratylenchus penetrans and the ectoparasitic Tylenchorhynchus dubius. Results Defoliation increased the total abundance of P. penetrans and the number per unit root mass (density) of both P. penetrans and T. dubius. Defoliation enhanced the density of P. penetrans, however, only when plants were defoliated early. Timing did not influence the density of T. dubius, although both abundance and density increased over time. Defoliation increased the nitrogen concentration of plant roots, but reduced root biomass. The strongest reduction of root biomass occurred after early defoliation. Conclusions Our study indicates that plant responses to aboveground herbivory and their effects on belowground herbivores can be influenced by the time when plants are defoliated, as well as by the belowground herbivore species and their interactions