Abstract: Delineation of regional boundary is an important procedure in ecological regionalization, but at present, this delineation for aquatic eco-regionalization is mostly dependent on qualitative analysis and expert judgment. In this paper, a two-level eco-region framework was established to delineate the aquatic eco-regions in Erhai Lake Basin. In this framework, sub-basin was taken as the basic unit based on GIS technique, and the indices for the two-level regionalization were quantitatively screened by correlation analysis. Altitude, slope, and normalized difference vegetation index were identified as the indices for level I, and farmland and urban area percentages were the indices for level Ⅱ. The index maps were overlaid and reclassified, and the sub-basins were further merged into several regions. Five levelI eco-regions and nine levelⅡ eco-regions were delineated finally. The examination through the comparison of the distribution of algal communities in different eco-regions showed that the regionalization result was reasonable. It was suggested that applying quantitative analysis and sub-basin boundaries in aquatic eco-regionalization could make the delineation of regional boundary more scientific and the actual management more operational. This study provided a new method for the study of aquatic eco-egionalization, and the basic units for the aquatic ecological management of Erhai Lake Basin.

Key words: forest ecosystem, carbon stock, carbon sequestration, regional distribution.