Functional, temporal and spatial complementarity in mammal‐fungal spore networks enhances mycorrhizal dispersal following forest harvesting

Abstract

In temperate forests, nearly all tree species form a symbiotic relationship with either arbuscular mycorrhizal (AM) or ectomycorrhizal (ECM) fungi. These fungi colonize plant roots and increase nutrient and water uptake of trees. Small mammals such as mice, voles, and chipmunks play an important ecological role by consuming the fruiting bodies of mycorrhizal fungi (truffles and mushrooms) and dispersing spores to new areas. This dispersal is particularly important as trees regenerate following disturbances such as timber harvests. For effective fungal spore dispersal, small mammals must disperse spores of the correct functional type (AM or ECM fungi), in sufficient quantities, and to appropriate microsite locations where tree seedlings are regenerating. Determining the relative role of small mammal species in dispersing mycorrhizal fungi is key to understanding how to maintain these important mammal-fungal interactions in managed systems. To examine the functional, temporal, and spatial components of mycorrhizal fungal spore dispersal by small mammals following timber harvest, we live trapped and collected scat from rodents and shrews in small patch cuts in the northeastern USA. We tracked the interactions of seven small mammal species and 34 fungal taxa over a two year period directly following harvests. Additionally, we measured species-specific microhabitat associations of small mammals to determine where species deposited spores. We found that small mammal species were complementary in the functional type of fungi that they dispersed, with some species primarily dispersing AM fungal spores and others dispersing ECM fungal spores. However, more species consumed AM fungi, making dispersal of AM spores more robust to changes in the small mammal community compared to ECM spores, which were primarily dispersed by just two small mammal species. Small mammal species varied from having no microhabitat associations to associating with a variety of different conditions, indicating that species play different roles, from broadcasting spores widely to depositing spores in discrete locations. By preserving and enhancing microhabitat characteristics that are associated with small mammals in harvested areas, particularly for species that disperse ECM fungi, forest managers can help maintain dispersal of mycorrhizal fungi by small mammals.