Methane emission from Yangtze estuarine wetland, China

Abstract

[1] Yangtze estuary, lying in the subtropical monsoon region of China, is characterized by a unique environmental setting and endemic wetland plant species (Scirpus mariqueter). Methane (CH 4 ) emission fluxes were measured at the Yangtze estuarine wetland, Chongming Dongtan (CD), by a static closed chamber technique from May 2004 to April 2005. The results showed that CD is the source of atmospheric CH 4 , and emission fluxes had significant diurnal and seasonal variation. The annual average CH 4 emission flux was 2.06 mg m À2 h À1 at the CD marsh site and 0.04 mg m À2 h À1 at the CD bare tidal flat (nonvegetated). Wetland plant species (S. mariqueter) and temperature were the primary factors controlling the CH 4 emission. The results of the light and dark chamber comparison and plant shoot clipping experiment suggest that molecular diffusion and convective gas flow methods were the two main mechanisms of CH 4 transported via S. mariqueter plants in July. However, molecular diffusion was believed to be the primary transport mechanism from August to October, with leaf resistance as one of the factors regulating CH 4 diffusion. There was significant correlation between CH 4 fluxes and temperature, especially the 10 cm depth ground temperature (R 2 = 0.7784). Although sediment organic carbon content did not determine CH 4 fluxes, net ecosystem production was significantly correlated with CH 4 fluxes, suggesting that the photosynthates of S. mariqueter effectively provided the substrate for methanogenic bacteria.

Effects of semi-lunar tidal cycling on soil CO2 and CH4 emissions: a case study in the Yangtze River estuary, China

“…This suggests that the overall, soil carbon emissions would probably be overestimated if soil CO 2 and CH 4 effluxes are only measured during NTP in wetlands of the Yangtze River estuary, such as in Wang et al (2009).…”

“…For instance, several laboratory incubation studies indicated that artificially simulated seawater addition increased soil CO 2 and CH 4 production compared with freshwater controls (Weston et al 2011), and induced a brief stimulation of soil CO 2 production but continuous suppression of CH 4 production, as compared with dilute seawater controls (Chambers et al 2011). However, in situ measurements of GHG effluxes in most studies were made while tidal flats were not inundated by tidewater, such as in Chen et al (2012), Livesley and Andrusiak (2012) and Wang et al (2009), probably because of operational difficulties during tidal inundations. Thus, estimated GHG emissions from coastal wetland soils have large uncertainties because of insufficient data reflecting tidal effects.…”

Salinity Influence on Methane Emissions from Tidal Marshes

“…In three of the studies, both light and dark measurements were made, allowing a day length-integrated rate to be calculated for a 24-h period. We used the day length-integrated rate reported by Van der Nat and Middelburg (2000) in our analysis, and calculated such a rate from data reported by Hirota et al (2007) and Wang et al (2009) (Table 1).…”

Spatial variations in methane emissions from natural wetlands in China

“…Yangtze and Min River Estuary, Taihu, Taiwan, and Hainan attracted much attention (Lu et al 1999;Chang and Yang 2003;Wang et al 2009a;Tong et al 2010). These studies showed that CH 4 emissions from herbaceous swamps were much higher than those from mangroves, and the emission rates from beaches were greatly influenced by tidal stages.…”