Erschienen:
American Geophysical Union (AGU), 2009
Erschienen in:Journal of Geophysical Research: Biogeosciences
Sprache:
Englisch
DOI:
10.1029/2008jg000857
ISSN:
0148-0227
Entstehung:
Anmerkungen:
Beschreibung:
<jats:p>Yangtze estuary, lying in the subtropical monsoon region of China, is characterized by a unique environmental setting and endemic wetland plant species (<jats:italic>Scirpus mariqueter</jats:italic>). Methane (CH<jats:sub>4</jats:sub>) 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<jats:sub>4</jats:sub>, and emission fluxes had significant diurnal and seasonal variation. The annual average CH<jats:sub>4</jats:sub> emission flux was 2.06 mg m<jats:sup>−2</jats:sup> h<jats:sup>−1</jats:sup> at the CD marsh site and 0.04 mg m<jats:sup>−2</jats:sup> h<jats:sup>−1</jats:sup> at the CD bare tidal flat (nonvegetated). Wetland plant species (<jats:italic>S. mariqueter</jats:italic>) and temperature were the primary factors controlling the CH<jats:sub>4</jats:sub> 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<jats:sub>4</jats:sub> transported via <jats:italic>S. mariqueter</jats:italic> 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<jats:sub>4</jats:sub> diffusion. There was significant correlation between CH<jats:sub>4</jats:sub> fluxes and temperature, especially the 10 cm depth ground temperature (<jats:italic>R</jats:italic><jats:sup>2</jats:sup> = 0.7784). Although sediment organic carbon content did not determine CH<jats:sub>4</jats:sub> fluxes, net ecosystem production was significantly correlated with CH<jats:sub>4</jats:sub> fluxes, suggesting that the photosynthates of <jats:italic>S. mariqueter</jats:italic> effectively provided the substrate for methanogenic bacteria.</jats:p>