| Project/Area Number |
16380168
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Agricultural environmental engineering
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| Research Institution | The University of Tokyo |
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Principal Investigator |
KOBAYASHI Kazuhiko The University of Tokyo, Graduate School of Agricultural and Life Sciences, Professor, 大学院・農学生命科学研究科, 教授 (10354044)
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| Co-Investigator(Kenkyū-buntansha) |
NAKAMOTO Tomomi The University of Tokyo, Graduate School of Agricultural and Life Sciences, Associate Professor, 大学院・農学生命科学研究科, 助教授 (50180419)
ABE Jun The University of Tokyo, Graduate School of Agricultural and Life Sciences, Assistant, 大学院・農学生命科学研究科, 助手 (60221727)
SASAKI Haruto The University of Tokyo, Graduate School of Agricultural and Life Sciences, Assistant, 大学院・農学生命科学研究科, 助手 (60225886)
INUBUSHI Kazuyuki Chiba University, Faculty of Horticulture, Professor, 園芸学部, 教授 (00168428)
OKADA Masumi National Agricultural Research Center for Tohoku Region, Team Leader, 東北農業研究センター, チーム長(研究職) (10355274)
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| Project Period (FY) |
2004 – 2005
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| Project Status |
Completed (Fiscal Year 2005)
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| Budget Amount *help |
¥15,300,000 (Direct Cost: ¥15,300,000)
Fiscal Year 2005: ¥4,900,000 (Direct Cost: ¥4,900,000)
Fiscal Year 2004: ¥10,400,000 (Direct Cost: ¥10,400,000)
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| Keywords | CO_2 / carbon dioxide / methane / rice / lowland field / root / cultivar / FACE / CO_2 / 気泡 / 炭素同位体 |
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| Research Abstract |
We studied impacts of elevated atmospheric CO_2 concentration ([CO_2]) on carbon and nitrogen metabolisms in plant-soil systems under flooded lowland rice production with the major thrusts on the changes in root dynamics, soil dissolved organic carbon and methane emission. The results are summarized as follows :
In a free-air CO_2 enrichment (FACE) experiment, a nominal increase of [CO_2] by 200 ppm increased rice grain yield by 15 %, which was unchanged by applying nitrogen fertilizer beyond the recommended amount, but was reduced to 7 % when the fertilization rate was halved. Root dynamics studied in the FACE experiment by using root-bags and minirhyzotron showed that elevated [CO_2] enhanced new root formation during the vegetative stage, had no effect during the flowering stage, and accelerated root death for mid- to late- maturity stages.
In a sun-lit chamber experiment, an elevation of [CO_2] by 200 ppm increased methane (CH_4) emission for all four rice varieties, which differed i
… More
n CH_4 emission rate but showed no difference in the increase of CH_4 emission due to [CO_2] enrichment. There was no clear difference between [CO_2] levels in dissolved CH_4 concentration in soil water, whereas dissolved organic carbon concentration was increased by [CO_2] elevation in all the varieties. Three of the four varieties showed lower activity of CH_4 oxidation under elevated [CO_2], while one variety showed the opposite response. In the same chamber experiment, it was shown that CH_4 accumulation in soil gas phase can be monitored by using minirhizotron and evaluated by the area of air bubbles in images of the soil profile. The association of air bubbles with roots clearly showed the contribution of rhizodeposition to CH_4 generation. Area of air bubbles was increased by the [CO_2] elevation, which indicated increase of CH_4 generation. The chamber experiment was simulated with a biogeochemistry model : DNDC, which showed an increase in CH_4 emission under elevated [CO_2] in accordance with the observations. The model was also able to simulate seasonal change in the CH_4 emission, whereas it deviated from the observations with respect to the varietal difference in CH_4 emission. Less
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