A natural corollary to the rules which is also implicit in this model is that, depending on
the intensity and relative importance of constraints operating at the upper levels of the
hierarchy, the role of soil invertebrates as measured by their effect on rates of a specific
ecosystem process may, or may not, be significant. In the former case, discussing their
function is a relevant issue; in the latter, invertebrates may simply be used as indicators
of ecosystem function since their impact is not significant to soil functioning.