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 (480KB)
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25,217,000Yen (FY1998;8,061,000Yen)
Land-use/cover features are changing due to the large scale deforestation in South Asia. The emission inventory of green-house gases, especially carbon dioxide (CO2) is investigated through the field observation. The main sources in this case are soil and covered vegetation. The flux from soil to the atmosphere is measured using the chamber and the flux from vegetation to the atmosphere is measured by the eddy correlation system over the canopy layer. Chambers were set at different land-use/cover in Pasirmayan, Jambi Province, Sumatra. Eddy-correlation system is to set up at Pusrehut, Kalimantan Timur.
The CO2 flux from soil is large during rainy season and small dry season. This tendency is found at all test sites. CO2 flux in dry season at open space after the slash-and-burn is smaller than other site due to the soil desiccation. The fluxes in rain and dry seasons are smaller than the former researches at the tropical moist forest and dry forest, Nitrogen isotope ratios (¦Ä 15N) as well as CN ratios of soil organic matters (SOM) were determined. The results were compared with those for soil CO2 emission to determine possible relationship between the soil characteristics and the CO2 emission. The SOM accumulation was restricted in the top-soil (0-10 cm), demonstrating that the nitrogen dynamics in soil-plant system was under control of soil mineralization process. The ¦Ä 15N of SOM negatively correlated with the CN ratio, probably due to loss of isotopically lighter nitrogen by denitrification process during the nitrogen turnover. As the CN ratio is known to decrease as the SOM is decomposed, the ¦Ä 15N variation can be proposed as an indicator for the availability of easily decomposable organic matters (EDOM) in soil. The variation in CO2 emission from soils under different land-use during dry season was in accordance with the EDOM availability in top-soils that was predicted from the ¦Ä 15N variation. This fact suggests that the variation in soil CO2 emission among sites under different land-cover can be attributed to the change in availability of the EDOM.
The CO2 concentration over canopy layer shows typical diurnal change. Seasonal ehange in the trace of CO2 concentration is not found in one year observation since February 1998. This may say the characteristic feature for tropical rain forest but difference is found in satellite NDVI.
land-use/cover change, CO2 flux soil organic matter nitrogen isotope ratio, CO2 concentration