Estimation of pathways of the production of greenhouse gases in the tropical swamp forest in Thailand by stable isotope investigation

Abstract

Dynamics of greenhouse gases (N₂O and CH₄) with the dry–wet cycle along with the variation of oxidation–reduction boundaries were investigated in the tropical wetland in monsoon Asia. It was clarified that the production of N₂O and CH₄ was closely related to the development of a redox boundary in the Bang Nara River systems. An intermittent increase in N₂O was observed at the beginning of the rainy season, when a large amount of easily decomposable organic matter was introduced into the river. After 10 days, when dissolved oxygen was consumed completely at the middle reaches, the emission of CH₄ became maximal due to the possible occurrence of denitrification. The distribution of stable isotope ratios in N₂O clearly demonstrated that nitrification is the major process for its production. Furthermore, the production of N₂O in this study area was found to vary in time and space with changes in the redox boundary along the water flow.

Keywords:

• greenhouse gases
• methane
• nitrogen-15
• nitrous oxide
• oxygen-18
• tropical swamp

Acknowledgements

This study was supported by the Grant-in-Aid for IGBP-MESSC (09041159) and Creative Basic Research for Tropical Swamp Forest (09NP0901) from the Japan Ministry of Education, Sciences, Sports, and Culture (MESSC).