Two approaches were used to quantify the methane and carbon dioxide fluxes from two peatland areas (Oukoop and Stein in The Netherlands) under different water table regimes during the period 2005 – 2007. Methane and carbon dioxide fluxes were determined using data from chamber flux measurements. Analysis of the chamber flux measurements yielded average fluxes of methane and carbon dioxide of 113.3 ± 23.0 ton CO2 ha-1 and 0.73 ± 0.53 ton CH4 ha-1 at Oukoop and 93.1 ± 19.7 ton CO2 ha-1 and 0.69 ± 0.54 ton CH4 ha-1 at Stein. Comparison of these results with daily measurements at the same location, show that the discontinuous chamber flux measurements and daily flux measurements yield different results which can be attributed to method and scale of data gathering and the data analysis that was applied. Furthermore, the CO2 fluxes were derived from respiration data instead of NEE data which were not measured with the flux chamber measurements.
Correlation analysis showed that there was no consistent trend between water table level and CO2 and CH4 emissions and between (air) temperature and these emissions. This inconsistency can be attributed to the fact that CO2 and CH4 emissions cannot only be related to water table level, but are determined by many other factors which have not been studied in this research.
The model FOURSCALES was then used to simulate the effect of water table management on the emissions of methane and carbon dioxide. These model results were also compared with data obtained from daily flux measurements at these locations. Despite incomplete parameterization of the model, simulations with real measured ground water levels gave carbon dioxide fluxes that corresponded well with the real measured carbon dioxide fluxes.
Simulations with different water table levels were carried out to study the effect of water table management on carbon dioxide and methane fluxes. Model results show that a water table level of 30 cm below the field will result in minimum changes of CO2 and CH4 emissions.
A sensitivity analysis of parameters (specific root length, electron acceptors in reduced and oxidized form, time constant of labile and stabile carbon) showed only big changes in methane fluxes but not for carbon dioxide fluxes. Electron acceptors in reduced and oxidized form, time constant of labile and stabile carbon affected methane fluxes in different ways such as increasing or reducing the environment necessary or unfavourable (oxic or reduced conditions) for methane production or reducing or increasing the available carbon for methane production. Methane and carbon dioxide production are controlled by different processes and different parameters affect the production of these gases in different ways. Testing the effect of a parameter does not have to result in an increase or decrease of both studied greenhouse gases, as was shown in this study.