Doctor of Philosophy (PhD)


Renewable Natural Resources

Document Type



Methane has a warming potential 28 times that of carbon dioxide and has been increasing in the Earth’s atmosphere since 1750. An understanding of the dynamics of methane emissions from natural sources is becoming increasingly important as we may need to mitigate emissions from these sources in the future to help reduce the effects of climate change. Wetlands are the single largest natural source of methane; however, little attention has been given to how plant species, biota, and interactions between above and belowground communities and microbial communities may affect methane emissions. First, microbial community structure and function was assessed for two salt marsh plant species, Spartina alterniflora and Juncus romerianus via bacterial, archaeal, and fungal gene fragments, and extracellular enzyme assays to determine whether wetland microbial communities were structured by vegetation, and whether communities were functionally different. Bacterial communities were differentiated by plant species in two of three sites, suggesting while vegetation likely plays a role in structuring these communities, specific site characteristics are likely of equal importance. Fungal communities were influenced more by site than vegetation, and archaeal communities appeared to be structured by vegetation. Second, four freshwater wetland plants (Sagittaria lancifolia, Panicum hemitomon, Eleocharis macrostachya, Echinochloa walteri) were transplanted and grown in large mesocosms, and clipped to differing heights under different nutrient treatments to detect changes in methane emissions, methanogen, and methanotroph communities. Methane emission rates were plant species specific, and a three way interaction indicated that species, nutrient level, and clipping level altered methane emission. Methanogen and methanotroph communities were not altered by the treatments. Lastly, densities of marsh periwinkle snails and southern ribbed mussels were manipulated inside fenced enclosures within a S. alterniflora salt marsh, and methane emissions and extracellular enzyme activities were measured over the course of a year. Southern ribbed mussels increased the emission of methane when present, but marsh periwinkle snail density had no effect. The data collected show that microbial community structure in wetlands are influenced by vegetation, that methane emission rates are plant species specific, and that southern ribbed mussels have the potential to increase methane emissions from S. alterniflora marshes.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Nyman, John Andrew