Abstract:
Mangrove forest is one of the net sources of the atmospheric methane. The magnitude of emission from this source varies from location to location due to the difference of local factors. This study aims to investigate methane emission variations among different plant species and to understand environmental factors influencing emissions from the mangrove ecosystem in Thailand, focused on Kung Kraben Bay (KKB) and Ranong Biosphere Reserve (RN). Methane was measured by using a closed chamber technique, and analyzed by gas chromatography with a flame ionization detector. The results revealed that methane emissions from different mangrove plants were different, emission rate was the highest at Avicennia spp. and the lowest at Rhizophora spp. The higher flux from Avicennia spp. and Sonneratia spp. was associated with the presence of pneurnatophore (aerial root). Methane emissions showed both diurnal and seasond variations. Tidal fluctuation was the important factor of diurnal variation. During the low tide period methane emission was higher than during the high tide period. Furthermore, seasond variations of methane emissions at KKB site led to a positive correlation with soil temperature, resulting in the highest methane emission during summer and the lowest emission during cold season. While, at the RN site seasonal variation of methane emission led to a negative correlation with water conductivity. As the highest methane emission occurred during the rainy season (the lowest water conductivity values) and the lowest emission occurred during the cold season (the highest water conductivity values). The spatial variation of methane emission between different sites depended on both sulfate concentration and organic matter content in soil. The methane emission led to a negative correlation with sulfate and the positive correlation with organic matter content. The estimated annual rates of methane emission from KKB, at Rhizophora spp., Avicennia spp., Sonneratia spp. were 125.30 mg/m2, 250.97 rng/m2, 178.61 mg/m2, respectively and from Ranong Biosphere Reserve (RN) at Rhizophora spp. and Avicennia spp. were 157.32 mg/rn2, 645.45 mg/m2, respectively.
King Mongkut's University Technology Thonburi. Library