Two common ways that forest fungi spread to new locations are by releasing spores into the wind, and through transport by animals, including the consumption – and defecation – of fungal spores by rodents and other mammals. However, although fungi are arguably just as important to forests as trees, ecologists know much less about how they reproduce in a forest than about plant pollination and propagation.
University of New Hampshire researchers have found that relatively few fungi rely substantially on both processes. As reported in the June 2023 issue of Ecology, the researchers discovered that wind carried the smaller spores of many tree fungi, such as polypores and shelf fungi, as well as wood and leaf litter decomposers and plant pathogens. In contrast, rodents, through their scat, generally dispersed larger spores, including those of many mycorrhizal species.
Led by University of New Hampshire graduate student Ben Borgmann-Winter, the research team, which also included scientists from University of Vermont and ETH Zürich, conducted the study in a northern mixed hardwood forest at the Second College Grant in Coos County, New Hampshire. In both experimental harvest gaps and surrounding undisturbed woods, researchers live-trapped chipmunks, southern red-backed voles, and woodland jumping mice and collected scat from the traps before marking and releasing the animals. They also collected aerial spores using screened funnel traps near the ground. They then examined and identified the spores with both DNA analysis and microscopes.
When the researchers compared spore communities in the harvest area and surrounding forest, they found little difference for the spores transported by the three rodent species. In contrast, the communities of wind-dispersed spores differed between the two areas, with some species of spores missing from the harvest areas, likely because wind only carries spores so far. Given their association with mycorrhizal fungi, and their effectiveness spreading spores – producing tens to hundreds of fecal pellets every day (each pellet containing many thousands of spores) – rodents and other small mammals appear to be especially important for reintroducing fungi after forest disturbances.