Omnivory in soil systems is facilitated by the allometric distribution of trophic links’ lengths

The real occurrence of omnivory belowground is quite debated, as often the soil black box is idealized into a kind of larger-eats-smaller jungle law. Our aim is to propose and to illustrate the application of the lengths of trophic links to soil systems to better define the actual weight of omnivory for the structuring of ecological networks. We can in fact quantify mathematically the trophic links’ length (hereafter: TLL) on a Cartesian plane, making our indicator robust and different from the common links as simply parts of a given path or chain. We sought to explicitly test for relationships between length, frequency and distribution of all the trophic links computable for bacteria, fungi, protists and soil invertebrates and the omnivory of the latter. As only very few studies in literature quantified in orders of magnitude TLL, and as far as we know none investigated omnivory for entire soil biota, such an almost provocative approach is needed, making uniformity of terminology and unambiguousness of ecological meaning desirable.