Climate and site management as driving factors for the atmospheric greenhouse gas exchange of a restored wetland

[摘要] The atmospheric greenhouse gas (GHG) budget of a restored wetland in westernDenmark was established for the years 2009–2011 from eddy covariancemeasurements of carbon dioxide (CO₂) and methane (CH₄) fluxes. Thewater table in the wetland, which was restored in 2002, was unregulated, andthe vegetation height was limited through occasional grazing by cattle andgrass cutting. The annual net CO₂ uptake varied between 195 and983 g m⁻² and the annual net CH₄ release varied between 11 and17 g m⁻². In all three years the wetland was a carbon sink and removedbetween 42 and 259 g C m⁻² from the atmosphere. However, in terms ofthe full annual GHG budget (assuming that 1 g CH₄ is equivalent to25 g CO₂ with respect to the greenhouse effect over a time horizon of100 years) the wetland was a sink in 2009, a source in 2010 and neutral in2011. Complementary observations of meteorological factors and managementactivities were used to explain the large inter-annual variations in the fullatmospheric GHG budget of the wetland. The largest impact on the annual GHGfluxes, eventually defining their sign, came from site management throughchanges in grazing duration and animal stocking density. These changesaccounted for half of the observed variability in the CO₂ fluxes andabout two thirds of the variability in CH₄ fluxes. An unusually longperiod of snow cover in 2010 had the second largest effect on the annualCO₂ flux, whose interannual variability was larger than that of theCH₄ flux. Since integrated CO₂ and CH₄ flux data from restoredwetlands are still very rare, it is concluded that more long-term fluxmeasurements are needed to quantify the effects of ecosystem disturbance, interms of management activities and exceptional weather patterns, on theatmospheric GHG budget more accurately.

[学科分类] 地球化学与岩石