Anaerobic methanogenesis in wetland ecosystems: do cut emergent aerenchyma of Typha x glauca facilitate increased atmospheric methane emission?

Abstract

Anaerobic methanogensis by bacteria communities is a major source of global atmospheric methane and therefore an important area of concern regarding climate change. This is particularly relevant to wetland ecosystems whose warm, water-logged, oxygen-poor soil conditions are the ideal environment for the fermentation of methane. In addition to relatively slow diffusion of methane through soil and water, and the sudden ebullition of trapped gas pockets, the aerenchyma (vessel-like tubes composed of mostly airspace that transport essential gases throughout the plant) of plants provide a direct route for gases to reach the atmosphere through the aerenchyma. We tested our hypothesis at a wetland site on the coast of Lake Huron in Cheboygan County, MI called Cheboygan Marsh. Five bucket plots pairs were installed where each pair had one bucket with the Typha stems cut below the water (submerged) and the other had stems cut above the water (emerged). Methane emissions were measured from each plot and we concluded that there was a significantly higher methane flux from emergent Typha than submerged Typha.