The impact of experimental temperature and water level manipulation on carbon dioxide release in a poor fen in Northern Poland

Peatlands are ecosystems for which carbon budget relies strongly on the meteorological and hydrological conditions. Here, using a manipulative field experiment, we measured ecosystem respiration (RECO) over two years (2013–2014) in a poor fen in Poland to estimate the carbon emission in a changing climate. The experiment consisted of warming (open-top chambers - OTC) and water table manipulation. The application of OTC increased the mean values of daily maximum air temperature by approx. 1.1–1.8 °C. Warming or the increased water table depth separately resulted in an increase in ecosystem respiration by approx. 0.1 μmol CO2 m−2 s−1 and 0.3 μmol CO2 m−2 s−1, respectively. However, our results show also the additive nature of warming and water table drawdown impact on daily RECO during the studied years (2013–0.80 μmol CO2 m−2 s−1 and 2014–1.16 μmol CO2 m−2 s−1). With the natural dry period event which occurred in 2014, the seasonal RECO increased by approx. 0.2 μmol CO2 m−2 s−1 as compared to the previous year. Projected global warming will therefore significantly enhance C loss from poor fens in this region of Europe.