炭素?窒素安定同位体比に基づく流域圏生態系健全性評価法の開発

摘要

In this study, a new ecosystem assessment method using carbon and nitrogen stable isotope analysis is proposed to evaluate health of river basin ecosystem. The health is mainly based on the material cycling through river, and therefore is able to evaluate by the stable isotope ratios of carbon (δ~(13) C) and nitrogen (δ~(15)N) in the sediments between river mouth and upstream end. The index of health is defined as dimensionless shift length of observed value from ideal value in three dimensional map δ~(15)N-δ~(13)C-L (distance from river mouth). This ecosystem assessment method is applied to the various rivers in the main island of Okinawa. The result shows that the dimensionless shift length can be a reasonable index of health in the river basin ecosystems.