Processes driving the production, transformation and transport of methane (CH₄) in wetland ecosystems are highly complex. We present a simple calculation algorithm to separate open-water CH₄ fluxes measured with automatic chambers into diffusion- and ebullition-derived components. This helps to reveal underlying dynamics, to identify potential environmental drivers and, thus, to calculate reliable CH₄ emission estimates. The flux separation is based on identification of ebullition-related sudden concentration changes during single measurements. Therefore, a variable ebullition filter is applied, using the lower and upper quartile and the interquartile range (IQR). Automation of data processing is achieved by using an established R script, adjusted for the purpose of CH₄ flux calculation. The algorithm was validated by performing a laboratory experiment and tested using flux measurement data (July to September 2013) from a former fen grassland site, which converted into a shallow lake as a result of rewetting. Ebullition and diffusion contributed equally (46 and 55 %) to total CH₄ emissions, which is comparable to ratios given in the literature. Moreover, the separation algorithm revealed a concealed shift in the diurnal trend of diffusive fluxes throughout the measurement period. The water temperature gradient was identified as one of the major drivers of diffusive CH₄ emissions, whereas no significant driver was found in the case of erratic CH₄ ebullition events.

Peat extraction leaves a land surface with a strong relief of deep cutover areas and higher ridges. Rewetting inundates the deep parts, while less deeply extracted zones remain at or above the water level. In temperate fens the flooded areas are colonized by helophytes such as Eriophorum angustifolium, Carex spp., Typha latifolia or Phragmites australis dependent on water depth. Reeds of Typha and Phragmites are reported as large sources of methane, but data on net CO₂ uptake are contradictory for Typha and rare for Phragmites. Here, we analyze the effect of vegetation, water level and nutrient conditions on greenhouse gas (GHG) emissions for representative vegetation types along water level gradients at two rewetted cutover fens (mesotrophic and eutrophic) in Belarus. Greenhouse gas emissions were measured campaign-wise with manual chambers every 2 to 4 weeks for 2 years and interpolated by modelling. All sites had negligible nitrous oxide exchange rates. Most sites were carbon sinks and small GHG sources. Methane emissions generally increased with net ecosystem CO₂ uptake. Mesotrophic small sedge reeds with water table around the land surface were small GHG sources in the range of 2.3 to 4.2 t CO₂ eq. ha⁻¹ yr⁻¹. Eutrophic tall sedge – Typha latifolia reeds on newly formed floating mats were substantial net GHG emitters in the range of 25.1 to 39.1 t CO₂ eq. ha⁻¹ yr. They represent transient vegetation stages. Phragmites reeds ranged between −1.7 to 4.2 t CO₂ eq. ha⁻¹ yr⁻¹ with an overall mean GHG emission of 1.3 t CO₂ eq. ha⁻¹ yr⁻¹. The annual CO₂ balance was best explained by vegetation biomass, which includes the role of vegetation composition and species. Methane emissions were obviously driven by biological activity of vegetation and soil organisms. Shallow flooding of cutover temperate fens is a suitable measure to arrive at low GHG emissions. Phragmites australis establishment should be promoted in deeper flooded areas and will lead to moderate, but variable GHG emissions or even occasional sinks. The risk of large GHG emissions is higher for eutrophic than mesotrophic peatlands. Nevertheless, flooding of eutrophic temperate fens still represents a safe GHG mitigation option because even the hotspot of our study, the floating tall sedge – Typha latifolia reeds, did not exceed the typical range of GHG emissions from drained fen grasslands and the spatially dominant Phragmites australis reed emitted by far less GHG than drained fens.

Bioenergy crop production is rapidly expanding in Europe, and the potential emissions of biogenic volatile organic compounds (BVOCs) might change the chemical composition of the atmosphere, influencing in turn air quality and regional climate. The environmental impacts of bioenergy crops on air chemistry are difficult to assess due to a lack of accurate field observations. Therefore, we studied BVOC fluxes from a bioenergy maize field in North‐Eastern Germany throughout the entire reproductive growth stage of the plants. Combining automated large chambers and proton transfer reaction mass spectrometry (PTR‐MS), we successfully measured fluxes of the highly reactive hydrocarbons monoterpenes (MTs) and sesquiterpenes (SQTs), together with several other BVOCs, including alcohols, aldehydes, ketones, benzenoids, and fatty acid derivatives. Emissions of MTs and SQTs were relatively high (17.0% and 3.6% of total mean molar BVOC emission, respectively) compared to methanol emissions (17.6%). Seasonal MT and SQT fluxes were clearly associated with the flowering phase, originating mainly from the flowering tissues as shown in additional laboratory experiments. From the observations of CO₂ net ecosystem exchange and evapotranspiration rates, we could exclude heat and drought stress‐induced BVOC emissions. Standard emission factors calculated for all compounds, chemical groups, and growth stages, showed that the temperature dependency of volatile terpenoid fluxes decreased distinctively with proceeding development stage. The results indicate that emissions from large‐scale bioenergy maize fields should be better differentiated and considered in regional estimates of aerosol formation. For the implementation of such relation into biogeochemical modelling, it should be considered that not only seasonal weather development but also phenological growth stages are determining the BVOC patterns and emission potentials.