Effects of timber harvest on epigeous fungal fruiting patterns and community structure in a northern hardwood ecosystem

Abstract

Epigeous fungal fruiting has important impacts on fungal reproduction and ecosystem function. Forest disturbances, such as timber harvest, impact moisture, host availability, and substrate availability, which in turn may drive changes in fungal fruiting patterns and community structure. We surveyed mushrooms in 0.4-ha patch cuts (18 months post-harvest) and adjacent intact hardwood forest in northern New Hampshire, USA, to document the effects of timber harvest on summer fruiting richness, biomass, diversity, and community structure of ectomycorrhizal, parasitic, and saprobic mushroom taxa. Fungal fruiting richness, diversity, and community heterogeneity were greater in intact forests than patch cuts. Among functional groups, ectomycorrhizal fruiting richness, diversity, and biomass were greater in unharvested areas than in the patch cuts, but parasitic and saprobic fruiting did not differ statistically between the two forest conditions. Our findings suggest that timber harvest simplifies fungal fruiting communities shortly after harvest, in particular triggering declines in ectomycorrhizal taxa which are important symbionts facilitating tree establishment and regeneration. Multi-aged silvicultural practices that maintain mature forest conditions adjacent to and throughout harvested areas through deliberate retention of overstory trees and downed woody material may promote fungal fruiting diversity in regenerating stands.

Wind and small mammals are complementary fungal dispersers

“…Reported rodent home range sizes are similar to our findings (0.36–2.29 ha; see Appendix S1: Figure S6), suggesting that dispersal by small mammals may on occasion be up to 200 m. Because all target species were frequently captured in both the forest and the harvest gaps, small mammals may play a role in returning forest fungi (particularly AM/ECM taxa), to disturbed areas. This conclusion is bolstered by our finding that macrofungal spore communities did not differ between scat samples collected in forests and harvest gaps, even though previous work from this site indicated that the macrofungal fruiting community itself did differ (Borgmann‐Winter et al, 2021).…”

“…To measure spore deposition by wind, we deployed six spore traps at each of the eight study sites for 2 weeks in August 2019. We selected this period to coincide with the approximate peak fruiting of mushrooms (Borgmann‐Winter et al, 2021) and truffles (Stephens et al, 2017) in this region, as well as to capitalize on the occurrence of both early‐ and late‐season fruiters during this period. Spore traps were placed 12 m apart, along a 60 m transect extending 30 m into the harvest gap and 30 m into the forest.…”

Seed or soil: tracing back the plant mycobiota primary sources

“…As for seedlings in vitro, a large share of in situ adult mycobiota is not explained by seeds or bulk soil. Contrary to the in vitro experiment, sources of contaminations in situ may be more diverse, including fungi dispersed by wind and small mammals (Zhou et al, 2021;Borgmann-Winter et al), or even plant debris from the litter (Christian et al, 2017). Though fungi may be transmitted by wind (e.g., spores), the low density of plant individuals (in particular H. salicornicum individuals; fertility islands hypothesis) may limit their dispersion and therefore favor the withholding of verticallytransmitted fungi in H. salicornicum leaves, while the mycobiota of belowground tissues are more likely to be influenced by the environment (horizontal transmission).…”