Date of Award

Spring 2022

Project Type

Thesis

Program or Major

Natural Resources

Degree Name

Master of Science

First Advisor

Rebecca J Rowe

Second Advisor

Serita D Frey

Third Advisor

Ryan B Stephens

Abstract

Forest-dwelling fungi are critical to ecosystem function in their roles as decomposers and nutrient cyclers, food sources, pathogens, and mycorrhizal symbionts. In northern New England, a region with a substantial timber industry, the degree to which fungal communities are resilient to timber harvest, as well as their ability to recolonize post-disturbance, may impact ecosystem function and forest regeneration. In this thesis, we investigate the impacts of (1) timber harvest on fungal fruiting, an important element of fungal reproduction, and (2) the dispersal mechanisms by which fungi may re-colonize harvested areas. In Chapter 1, we investigate the impact of timber harvest on epigeous fungal fruiting patterns. 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 x 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. In Chapter 2, we compare fungal spore dispersal between wind and small mammals. Spore dispersal has important impacts on fungal diversity and ecosystem function. Dispersal can occur via several mechanisms, but wind is perhaps the best-studied and is often assumed to be the primary dispersal mechanism for most aboveground fungi. Mycophagy is another commonly reported dispersal mechanism, particularly as performed by small mammals, which are often speciose and abundant in forested systems. Few studies directly compare wind- and mammalfacilitated spore dispersal. Thus, it is unclear whether these pathways are complementary or redundant in the taxa they disperse and the ecosystem functions they provision. Here we compare the diversity and morphology of fungi dispersed by wind and three species of small mammals (Myodes gapperi, Napaeozapus insignis, and Tamias striatus) in recently harvested patch cuts using a combination of microscopy and Illumina sequencing. We demonstrate that fungal communities dispersed by wind and small mammals differ in taxonomy and species xi richness, as well as functional group membership. A large proportion of wind-dispersed spores belong to wood saprotrophs, litter saprotrophs, mycoparasites, and plant pathogens, whereas most spores dispersed in mammal scat come from mycorrhizal and unspecified saprotrophic taxa. We note substantial dispersal of truffles, mushrooms, AM sporocarps, jellies, and crusts by small mammals. In addition, we find that mammal-dispersed spores are larger on average than wind-dispersed spores, but do not differ in melanization or the presence of ornamentation. We quantify dispersal distances of small mammals by modeling home range and core area size using kernel density estimators from mark-recapture survey data, finding the distance to be comparable to those reported in the literature for wind-based dispersal. Our findings suggest that wind- and small mammal-facilitated dispersal are complementary processes, which highlights the importance of maintaining robust small mammal communities, particularly following timber harvest.

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