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Greenhouse gas emissions were measured from tropical peatlands of Kalimantan, Indonesia. The effect of hydrological zone and land-use on the emission of N 2 O, CH 4 and CO 2 were examined. Temporal and annual N 2 O, CH 4 and CO 2 were then measured. The results showed that the emissions of these gases were strongly affected by landuse and hydrological zone. The emissions exhibited seasonal changes. Annual emission of N 2 O was the highest (nearly 1.4 g N m −2 y −1 ) from site A-1 (secondary forest), while there was no significant difference in annual N 2 O emission from site A-2 (paddy field) and site A-3 (rice-soybean rotation field). Multiplying the areas of forest and non-forest in Kalimantan with the emission of N 2 O from corresponding land-uses, the annual N 2 O emissions from peat forest and peat non-forest of Kalimantan were estimated as 0.046 and 0.004 Tg N y −1 , respectively. The emissions of CH 4 from paddy field and non-paddy field were estimated similarly as 0.14 and 0.21 Tg C y −1 , respectively. Total annual CO 2 emission was estimated to be 182 Tg C y −1 . Peatlands of Kalimantan, Indonesia, contributed less than 0.3% of the total global N 2 O, CO 2 or CH 4 emission, indicating that the gaseous losses of soil N and C from the study area to the atmosphere were small.

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This research aims at elucidating the greenhouse gas emissions and its related soil microbial properties in continuously flooded or intermittently drained paddy soils in Japan and Indonesia. The study in Japan comprises alluvial soil and peat, cultivated to rice variety Nipponbare, while in Indonesia comprised alluvial soil cultivated to rice variety Siam Pandak. Intermittent drainage was performed to half number of the plot in 6 days interval, starting at tillering or heading stage of rice, while the other half number of plot was kept flooded as control. The experiments were carried out to follow the randomized block design with three replications. Gas samples were taken in weekly basis, except during the treatments (i.e., every 2 days interval) and analyzed for methane (CH 4 ) and nitrous oxide (N 2 O) concentrations. Soil samples were and analyzed for the population of methanogenic bacteria, denitrifiers, methane production and consumption potentials, and methanogenic substrate. Plant growth parameters were also observed. The results showed that intermittent drainage significantly reduced greenhouse gas emission from paddy soil of Indonesia and Japan without significant changes in soil microbial population. The reductions of greenhouse emission from Japanese peaty and alluvial paddy soil due to intermittent drained were about 32 and 37%, respectively. Meanwhile, the reductions in greenhouse gas emission from alluvial soil of Indonesia due to intermittent drainage were very similar to that of in Japan, i.e., average about 37%. This suggests that intermittent drainage can be an appropriate technology option to reduce the greenhouse gas emission from paddy soil in Japan and Indonesia.

Effects of land-use change in tropical peatlands on the microbial population and emissions of nitrous oxide (N 2 O), methane (CH 4 ) and carbon dioxide (CO 2 ) were studied in the field and laboratory. The study area covered secondary forest, paddy field and paddy-soybean rotation field in Indonesia.ATP content, and numbers of viable bacteria and fungi, cellulolytic bacteria and fungi, NH 4 + oxidizers and denitrifiers in a paddy-soybean rotation field and paddy field were reduced to 1-30% and 3-90% of those in secondary forest, respectively. The field measurements of greenhouse gas emissions showed that significantly more CH 4 was emitted from paddy field than secondary forest, but no significant difference in the emission of either N 2 O or CO 2 . The laboratory incubation experiment showed that the soil moisture level and land-use change significantly affected the emission of N 2 O, CH 4 and CO 2 . These results suggested that land-use change significantly affected the microbial population and emissions of greenhouse gases.