Interactions among soil microbes or between soil microbes
and larger soil fauna have been shown to produce a wide variety
of responses in plants. For example, earthworms have been
shown to alter foliar nitrogen (Newington et al., 2004), and
combinations of earthworms and mycorrhizal fungi alter plant
quality through changes in constitutive levels of plant defensive
compounds (Wurst et al., 2004). The distribution of litter has
also been shown to influence plant defensive compounds (Wurst
et al., 2004).