Abstract
To characterize carbon and nitrogen stable isotope ratio of terrestrial materials is essential for the food web analysis in the paddy ecosystem. We have analyzed carbon and nitrogen stable isotope ratios of deciduous leaves, forest soil and canal sediment in a paddy field at hill-bottom (Yatsuda) area. Correlation was not observed between carbon stable isotope ratios (δ13C) of leaves and soil. However, negative correlation was observed between δ13C of soil and soil water content. It is likely that decomposition rate which will be considerably controlled by soil water content was involved with the δ13C values. Negative nitrogen stable isotope ratios (δ15N) of leaves indicated that forest in the Satoyama absorbed the nitrogen derived from rain water. There was correlation between δ15N of soil and soil water content at the right bank.δ15N values of sediment in the right canal where the water velocity is low were significantly higher than the left. Denitrification, which is affected by water velocity, will be promoted at the right bank. Ascents of δ13C and δ15N accompanied by decay of terrestrial organic matter mainly occur in terrestrial area in comparison with aqua area.
