Effects of flooding and drainage on CO2 flux in Dongting Lake wetlands, China

English Abstract:

Wetlands have been recognized as a main carbon sink on the earth. However, the role of carbon sink of flooding wetlands might be weakened due to the flooding duration time changes induced by anthropic disturbances. In this study, we quantified the effects of the flooding and drainage on CO₂ flux from a Miscanthus sacchariflorus marsh in Dongting Lake wetlands by eddy covariance technique from 20^th June to 31^st October, 2014. The results showed that the mean of CO₂ flux was -2.72μmol s^-1 m^-2 during 20^th June to 8^th July (before flooding), and it was reduced significantly to -4.29μmol s^-1 m^-2 during 9^th July to 30^th September (under flooding). However, the mean of CO₂ flux was 0.69μmol s^-1 m^-2 during 1^st to 31^th October (drained after flooding). The principal component analysis (PCA) among the environmental factors (water level (WL), sensible heat flux (H), latent heat flux (LE), air heat capacity (HC), air temperature (T), air pressure (P), air molar volume (molV), evapotranspiration (ET), water vapour density (WVD), relative humidity (RH), wind speed (S), friction velocity (U^*)) indicated that the CO₂ flux was mainly effected by WL and air properties (i.e., T, P, HC, molV, and WVD), which explained 44.78% of total variance, while the RH and energy characters (i.e., H, LE, ET) explained 24.91% of total variance and 14.58% of total variance was explained by S and U^*. Our results indicated that the flooding in wetlands can enhance the ability of carbon fixing while the drainage might accelerate the carbon loss. The artificial controlling of water level might be an effective way to fix the atmosphere carbon in flooding wetlands.