This post was inspired, once more, by wild boar as I have been considering their beneficial effects on ecosystems.
However, rooting activity (and, indeed, burrowing activity or other types of foraging that result in disturbance at the root level) is performed by many other species that can be herbivores (cervids, voles etc.), omnivores (bears etc.) and, indirectly (not aimed at the foraging on the root itself), by carnivores, as well (foxes, badgers etc.).
Some of these species and their activities might be relevant to this theory in the same manner wild boar are.
During such activities parts of the root system are disturbed and transferred (scattered).
These effects have been studied widely regarding the dispersal of the plants which roots have been foraged on (as endozoochory or exozoochory) (e.g., Karimi. S. et al., 2020).
My theory, meanwhile, concerns not the dispersal of the targeted plant (the foraging resource) but rather dispersal of associated fungal organisms or, more specifically, their propagules that have colonized root systems of the targeted plants or other nearby plants (e.g., arbuscular mycorrizha, ectomycorrizha etc.).
These organisms would likely become dispersed inadvertently through accidental consumption (surviving digestion and exiting the organism in the form of faeces), accidental transfer (through moving around the soil substrate or root parts etc.), through attachment to body parts of the animal engaged in the rooting activity etc.
Many of these fungal organisms are beneficial to the plants they colonize and some of them are parasites or even pathogens to the host plants.
Their redistribution might bear impact on the health and regeneration of the ecosystem.
My interest mostly lies, on this occasion, with a longer-distance dispersal of the fungal organisms and the potential of these fungi to colonize new areas, e.g., vegetation communities that belong to a succession state in which colonization by certain fungi might significantly alter the succession rates or dynamics by favouring or limiting some of the plant species.
For example, study by Terwilliger, J. & Pastor, J., 1999, suggests – low colonization rates by trees and shrubs on beaver meadows are not the result of the periodical flooding and inundation as much as they may be the result of lack of facilitation by beneficial ectomycorrizhal organisms that are not found in the soil of the beaver meadow and that are possibly limited in their dispersal from forest habitats to beaver meadow habitats.
Similarly, trees and shrubs might establish faster on grasslands if they form fungal associations that allow them to compete with grasses or other tall herbs.
In these circumstances, mammals that may assist the dispersal of symbiotic fungal organisms between different habitats (between a forest and a grassland etc.) could alter the successional dynamics.
Dynamics could be affected also by dispersal of parasitic fungi or pathogens.
Long distance dispersal is easier achieved by larger organisms (such as medium-sized or large mammals) that can distribute propagules in their faeces or attached to their fur, hooves etc.).
Trees and shrubs are not the only plants that are associated with the helping (or impeding) fungi.
Forbs can also benefit from fungal associations.
Propagule dispersal might be meaningful not only between different habitats but also between different patches (microhabitats) of the same larger habitat.
For example, it could assist colonization by woody plant or herbacous plant species of new patches distant to the parent individuals where the respective mycorrhizal organisms might not exist in the soil due to the lack of the associated plant species.
Mycorrhizal associations thus could prove essential for seedling establishment far from the population of origin.
It might be useful and interesting to study fungal propagule dispersal by wild boar and other rooting, burrowing etc. mammalian species between habitats or between habitat patches focusing on arbuscular mycorrizhal fungi and ectomycorrizhal fungi (although possibly also endomycorrizhal fungi because root-eaters penetrate the root cells of the plants, as well) and the consequent impacts on vegetation community regeneration, colonization or succession dynamics.
Notes by Ieva 