並列タイトル等熱帯泥炭地における泥炭分解および温室効果ガス放出に及ぼす土地利用変化と排水の影響
一般注記To evaluate the hypotheses that 1) plant-mediated oxygen supply should oxidize methane (CH4) produced in saturated tropical peat soil, and 2) this CH4 oxidation should reduce total global warming potential (GWP) in a tropical peatland, the author compared the fluxes and dissolved concentrations of greenhouse gases [GHGs; CH4, carbon dioxide (CO2), and nitrous oxide (N2O)] and dissolved oxygen (DO) at multiple peatland ecosystems in Central Kalimantan, Indonesia. Study ecosystems included tropical peat swamp forest and degraded peatland areas that were burned and/or drained during the rainy season. CH4 fluxes were significantly influenced by land use and drainage, which were highest in the flooded burnt sites (5.75±6.66 mgC m−2 h−1) followed by the flooded forest sites (1.37±2.03 mgC m−2 h−1), the drained burnt site (0.220±0.143 mgC m−2 h−1), and the drained forest site (0.0084±0.0321 mgC m−2 h−1). Dissolved CH4 concentrations were also significantly affected by land use and drainage, which were highest in the flooded burnt sites (124±84 μmol L−1) followed by the drained burnt site (45.2±29.8 μmol L−1), the flooded forest sites (1.15±1.38 μmol L−1), and the drained forest site (0.860±0.819 μmol L−1). DO concentrations were influenced by land use only, which were significantly higher in the forest sites (6.9±5.6 μmol L−1) compared to the burnt sites (4.0±2.9 μmol L−1). These results suggested that CH4 produced in the peat might be oxidized by plant-mediated oxygen supply in the forest sites. CO2 fluxes were significantly higher in the drained forest site (340±250 mgC m−2 h−1with the water table level of −20 to −60 cm) than in the drained burnt site (108±115 mgC m−2 h−1 with the water table level of −15 to +10 cm). Dissolved CO2 concentrations were 0.6 to 3.5 mmol L−1, also highest in the drained forest site. These results suggested the enhanced CO2 emission by aerobic peat decomposition and plant respiration in the drained forest site. N2O fluxes ranged from −2.4 to −8.7 μgN m−2 h−1 in the flooded sites and from 3.4 to 8.1 μgN m−2 h−1 in the drained sites. The negative N2O fluxes might be caused by N2O consumption by denitrification under flooded conditions. Dissolved N2O concentrations were 0.005 to 0.22 μmol L−1 but occurred at <0.01 μmol L−1 in most cases. GWP was mainly determined by CO2 flux, with highest levels in the drained forest site. The first hypothesis was supported given that 1) CH4 emissions in the flooded burnt sites were significantly larger than those in the flooded forest sites, 2) dissolved CH4 concentrations in the burnt sites were much higher than those in the forest sites, and 3) DO concentrations in the forest sites were significantly higher than those in the burnt sites and which was contributed on CH4 oxidation under water saturated condition. The CH4 flux and the dissolved CH4 concentration at a depth of 20 cm in the drained burnt site were similar to values observed in the forest sites, suggesting that CH4 oxidation in the surface soil layer occurred. The second hypothesis was weakly supported by the observed GWPs in the flooded burnt sites, which were 20% higher than those in the flooded forest sites. In this study, however, GWP was mainly determined by CO2 flux. Consequently, GWP and CO2 flux in the drained forest site were the highest for all study sites, and N2O flux made little contribution to GWP.
(主査) 教授 波多野 隆介, 教授 石黒 宗秀, 教授 平野 高司
農学院（環境資源学専攻）
コレクション（個別）国立国会図書館デジタルコレクション > デジタル化資料 > 博士論文
受理日（W3CDTF）2015-02-03T05:25:05+09:00
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