Wetlands are responsible for emitting 20-39% of total global methane (CH4), an important greenhouse gas that traps 24x more heat per molecule than CO2. Variation in wetland plant species composition may affect CH4 emissions by influencing the composition and activity of microorganisms producing CH4 in wetlands, by acting as conduits, via their aerenchyma, for emission from sediments to the atmosphere, and by providing methanogenic substrates for bacteria through their leaf litter. Wetlands are particularly prone to invasion, and even though only 6% of global landmass is made up of wetlands ~24% of the world’s most invasive plants species are wetland species. The ecological consequences of large plant species monocultures created by invasive plants altering or increasing wetland CH4 emissions is poorly understood. This research addresses the following questions: This research addresses the following questions: What is the relative importance of plants as a pathway for evasion of methane to the atmosphere and how do two common invasive wetland plants differ in their impact on the flux of methane from wetlands to the atmosphere? How does plant litter influence sediment methane release and how does this differ between cattail and phragmites? I sought to determine the relative importance of two common invasive wetland plants on methane emissions by measuring flux from Phragmites australis and Typha x glauca, in order to determine how these invasive species impact methane flux from wetlands. We used a closed system chamber to sample CH4 over time and used gas chromatography, with a flame ionizing detector (FID), to compare concentrations to a known standard. To determine how plant litter chemistry influenced methanogenesis, a mesocosm jar incubation study was performed, in which plant litter was incubated under anoxic conditions in the lab for one week after which CH4 flux was measured also using gas chromatography.
Results show that Typha x glauca had 3x greater CH4 emissions than Phragmites australis. Both species had 10x greater CH4 emissions than from their associated sediments alone. Results showed higher CH4 emissions from Phragmites australis litter than from Typha x glauca litter. These results demonstrate that CH4 emissions differ spatially when the plant community composition changes, and that presence and/or absence and species of plants existing in a wetland play an integral role in the amount of CH4 released into the atmosphere.