2005 Fiscal Year Final Research Report Summary
Emission and oxidation of CH4 and N2O in forest catchment and effect of hydrological process
| Project/Area Number |
15580124
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
林学・森林工学
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| Research Institution | HOKKAIDO UNIVERSITY |
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Principal Investigator |
SUGIMOTO Atsuko Hokkaido Univ., Faculty of Environ.Earth Sci., Prof., 大学院・地球環境科学研究院, 教授 (50235892)
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| Co-Investigator(Kenkyū-buntansha) |
SIBATA Hideaki Hokkaido Univ., Field Sci.Center for Northern Biosphere., Asso.Prof., 助教授 (70281798)
TAKAGI Kentaro Hokkaido Univ., Field Sci.Center for Northern Biosphere., Inst., 助手 (20322844)
OHTE Nobuhito Kyoto Univ., Grad.School of Agr., Asso.Prof., 大学院・農学研究科, 助教授 (10233199)
TOKUCHI Naoko Kyoto Univ., Grad.School of Agr., Asso.Prof., 大学院・農学研究科, 助教授 (60237071)
KOBA Keisuke Tokyo Inst.Tech., Interdisciplinary Grad.School of Sci.and Engineer., Lec., 大学院・総合理工学研究科, 講師 (90311745)
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| Project Period (FY) |
2003 – 2005
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| Keywords | carbon dioxide / methane / forest catchment / hydrology / anoxic environment / denitrification |
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| Research Abstract |
To elucidate the mechanisms of N_2O and CH_4 gas exchange in the forested catchment, the field experiments have been conducted at the Kiryu Experimental Watershed located in the southern Shiga prefecture, focusing on the hydrologic controls on biogeochemical processes for N_2O and CH_4 dynamics. Gas emitting rate and concentration in soil gas and dissolved gas concentration in soil and ground waters were measured both for CH_4 and N_2O at the stream side wetland and riparian zones in the headwater (zero-order) catchment. In addition to those observations, the stable isotope ratio of carbon in CH_4 was measured. The results provides following findings.
1.Continuous absorption was observed at the relatively dry soil in the Japanese cypress forest all through the year, while emission was constantly observed at the streamside wetland. Especially in the summer, the emission rate from the wetland was remarkably higher than the absorption rate at the slope side in the Japanese cypress stands.
2.CH_4 production and emission in the wetland was essentially controlled by soil temperature and groundwater level. Absorption was mainly controlled by the soil moisture content of surface horizon.
3.Seasonal variation in the d13C of CH_4 synchronized with that of dissolved CH_4 concentration in groundwater, suggesting that the major origin of CH_4 was the CO_2 produced by the decomposition of the organic matters mainly supplied by litter fall.
4.N_2O was mainly produced in the rim of the groundwater zone where the DOC was supply sufficiently from the slope side soils. The N_2O was considered to be produced through denitrification due to saturated condition in reduced environment below the groundwater level. In the deepest horizon in the groundwater zone, N_2O concentration was lower than that of ambient N_2O concentration, suggesting conversion of N_2O to N_2.
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