Ectomycorrhizal fungal communities in wind-disturbed forests
Cowden, Charles Clark
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In this dissertation, I describe the effects of wind disturbance in woody plant communities on the composition and structure of ectomycorrhizal fungal (EMF) communities. To evaluate these effects, EMF communities in windthrow gaps were compared to those in nearby undisturbed forests. A combination of morphotype analysis and molecular identification techniques were utilized to identify fungal species from EMF root tips. I first examined the effects of a catastrophic wind disturbance occurring in the fall of 2002 on EMF communities in a mixed oak and pine forest in northern Georgia. I was able to characterize both seasonal and annual differences between the gap and undisturbed forest EMF communities. The EMF community in the undisturbed forest was consistently more diverse that the EMF community in the windthrow gap, and composition of EMF differed substantially. The EMF assemblages did not differ significantly among seasons in the windthrow gap, but the EMF community during fall season in the undisturbed forest was significantly more diverse than in the spring or summer. The second study expands the temporal scale of the first study, and investigates the soil inoculum potential of EMF in different stages of forest recovery following windthrow. Soil was collected from disturbance gaps aged 2-, 11-, and 20- years since windthrow and from old-growth (undisturbed) forest stands in the Tionesta Scenic Area of western Pennsylvania, and soil inoculum potential was evaluated using a seedling bioassay. The results of this study suggest that compositional changes in the plant community strongly influence EMF community composition. Furthermore, there is a severity threshold for wind disturbance that must be crossed in order to affect EMF community composition. Lastly, I developed a computer simulation based on biological market theory that generates community composition hypotheses of fungal functional types under different environments that affect nutrient availability. The trade of carbon for nutrients based on the demands of both the host plant and the fungal functional types result in different fungal functional type assemblages when mineralized nutrients are readily available or when nutrients are bound in humified organic matter.