Abstract
This thesis describes the results of a four-year study into the CH4 cycle of freshwater marshes dominated by reed and bulrush. This research was conducted in the framework of the research theme carbon and nutrient dynamics in vegetated littoral systems of the department of Littoral Vegetation of the Centre for Estuarine and Coastal Ecology (Netherlands Institute of Ecology, Yerseke). Emphasis is given to the biogeochemical processes involved in the production, oxidation and transport of CH4. Reed and bulrush were selected as model plants on the basis of the significant differences in CH4 emission rates from reed and bulrush marshes in the Scheldt estuary. Moreover, reed and bulrush are used regularly in biological wastewater treatment facilities and the fundamental results of our study are therefore of great use to civil and environmental engineers designing and optimizing such constructed wetland filter beds. In situ rates of rhizospheric CH4 oxidation were measured and results showed a significant seasonal pattern for reed and bulrush and a significant difference between both plant species. The relatively large capacity of bulrush plants for rhizosphere oxidation apparently also attenuated availability of substrate for methane producing bacteria. A detailed experimentally derived CH4 balance revealed that this suppression of CH4 production was quantitatively a more important phenomenon than CH4 oxidation in attenuating CH4 emission
