Aboveground insects may also influence belowground communities
through other direct and indirect pathways (Hunter,
2001a). The quantity and quality of plant biomass have the
strongest influence over soil detrital communities (Wardle et al.,
2006). Herbivore changes in litter composition through the
induction of secondary compounds in leaf tissue will probably
influence decomposer communities (Fig. 3) although this has
yet be explicitly tested. Aboveground invertebrate herbivory has
also been shown to influence negatively root feeders (reviewed in
Masters & Brown, 1997). Herbivory by aphids, but not grasshoppers,
has been shown to increase collembola populations in
the top soil layer where host plant root density is reduced (Sinka
et al., 2007, 2009).