| 研究実績の概要 |
While the proposal has been adopted in November 2021, the research started in September 2022 due to the Covid 19 and border restrictions. However, the project was successfully completed.
Two additional team trips were organized this year, one in August 2023 (4 researchers + 3 students) and one in February 2024 ( 4 persons + 1 students) for intensive measurements and samplings (CH4 fluxes from soils and tree stems, soil CH4 concentration, microbiology, nitrogen cycling, soil nutrient capture).
The 18-month series of CH4 flux measurements showed a very clear effect of fertilization on the soil CH4 fluxes, not only reducing aerobic oxidation of methane as we hypothesized but also increasing methane production in the soil. We found that fertilization has turned a rubber plantation from sink to CH4 source. The reduction in soil methane oxidation was not related to difference in gas diffusivity. Higher nitrogen concentrations in the fertilized treatments inhibited methanotrophy and enhanced methanogenesis while concomitantly higher concentrations of dissolved organic carbon provided substrates for methanogenesis. Tree stems emitted methane but had a negligible contribution to the CH4 budget of a rubber plantation
Our Thai partners have successfully applied for a large “Reinventing KU” program which includes our JSPS project and through which two of us have been invited twice as Visiting Professors during the last fiscal year which allowed us to experiment in other provinces of Thailand, paving the road for a new research proposal.
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