Abstract: Agricultural non-point source pollution is the main factor of surface water eutrophication. Wetland landscape could retain pollutants or nutrients. Taking region as research object, we collected 36 samples of the surface water in the terraced wetland landscape of Dayutang village in Hani Rice Terraces in June (rainy season) and December (dry season) of 2017. We measured total nitrogen (TN) and total phosphorus (TP) concentrations, analyzed their temporal and spatial characteristics, and evaluated their eutrophication level and retention function by eutrophication composite index (PI) and retention capability, respectively. The results showed that the mean concentrations of TN and TP in all samples in the rainy season were higher than those in the dry season, with such values in ditch being the highest among the four wetland types. In terms of landscape types, the TN and TP concentrations in water from village and rice terraces were higher than those in forests and rivers. The PI value of all water samples in rainy season was higher than that in dry season. The ditch water was moderately eutrophic (with a PI value of 2.01) among the four water types, while the water in the landscape type of village was heavily eutrophic (PI 5.09). Furthermore, ditches (1.38 vs. 0.07 mg·L^-1), rice terraces (0.25 vs. 0.08 mg·L^-1), rice terraces area (2.04 vs. 0.17 mg·L^-1) and rivers (0.05 vs. 0.00 mg·L^-1) were of significant purification function, which kept the downstream river free of non-point source pollution and the entire landscape presenting obvious retention effects. Our results provide a basis for the ecological conservation of Hani Rice Terraces.

Key words: remote sensing ecological index, Poyang Lake area, spatial variation, influencing factor, ecological environment quality