| Project/Area Number |
17208028
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Boundary agriculture
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| Research Institution | Kyoto University |
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Principal Investigator |
KOSAKI Takashi Kyoto University, Graduate School of Global Environmental Studies, Professor (00144345)
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| Co-Investigator(Kenkyū-buntansha) |
NAWATA Eiji Kyoto University, Graduate School of Agriculture, Professor (30144348)
TANAKA Ueru Kyoto University, Graduate School of Global Environmental Studies, Associate Professor (10231408)
FUNAKAWA Shinya Kyoto University, Graduate School of Agriculture, Associate Professor (20244577)
YANAI Junta Kyoto Prefectural University, Graduate School of Agriculture, Associate Professor (00273491)
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| Project Period (FY) |
2005 – 2007
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| Project Status |
Completed (Fiscal Year 2007)
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| Budget Amount *help |
¥34,970,000 (Direct Cost: ¥26,900,000、Indirect Cost: ¥8,070,000)
Fiscal Year 2007: ¥4,290,000 (Direct Cost: ¥3,300,000、Indirect Cost: ¥990,000)
Fiscal Year 2006: ¥3,770,000 (Direct Cost: ¥2,900,000、Indirect Cost: ¥870,000)
Fiscal Year 2005: ¥26,910,000 (Direct Cost: ¥20,700,000、Indirect Cost: ¥6,210,000)
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| Keywords | amorphic properties of sesquioxides / climatic conditions / dissolved organic carbon / giostatistics / humid tropics / parameters / soil acidity / soil organic matter / 酵素活性 / ストレス要因 / 土壌微生物 / 有機物動態モデル / 乾湿変動 / 純一次生産量 / 人工降雨実験 / 土壌酸性化速度 / 土壌有機物動態 / 微生物バイオマス |
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| Research Abstract |
The main results obtained in the present study, in which soil organic matter (SOM) dynamics in humid tropics were investigated, are listed below:
1) In situ SOM dynamics were measured together with detailed monitoring on environmental conditions such as soil temperature and moisture, and parameters that primarily control the SOM dynamics in various regions of humid tropics were determined. The regions included: Japanese natural forests, Indonesia natural forest with different soil parent materials, shifting cropland fields and fallow forests used by Karen people in northern Thailand, sandy cropland in Northeast Thailand, and different home gardens in Indonesia.
2) To optimize regional crop rotation systems for mitigating SOC depletion, spatial and temporal variation of the SOM dynamics was analyzed using a giostatistics technique in sandy croplands in Northeast Thailand. A clear spatial variation was observed for organic C and N soil content, particle size distribution, and other related
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properties. The SOM dynamics and soil erosion were postulated to be driving forces behind the observed heterogeneity in soil properties. The results also indicated that the methodology of geostatistics were useful to simulate SOM dynamics in a regional scale considering spatial heterogeneity of soil resources according to topography.
3) Soil-related parameters controlling SOM dynamics were determined in different regions of humid tropics. The C and N dynamics in the shifting cropping fields in East Kalimantan were influenced by the degree of soil acidity. The volcanic-derived properties of soils (or amorphic properties of sesquioxides) also strongly controlled SOM dynamics in different soils investigated.
4) Thus the decomposition rates of SOM varied widely even in the limited areas of humid Asia, depending not only on climatic conditions but also on soil properties relating to particle size and/or amorphous characteristics, the latter of which reflects both the climatic (i. e., cool) and geological (i. e., volcanic origin) conditions. Soil acidity can affect C fluxes in different ways; that is, through changing decomposition rate constant and splitting ratio for decomposition to assimilation, or forming DOC that migrates to downward in soil profiles. Some of these conditions are specific for humid tropics. Therefore, these conditions should be taken into account to establish SOM dynamics model that could actually be applied to ecosystems in humid tropics. Less
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