Abstract: Based on allaround floristic information, and by using geographical information system and cluster analysis, this paper studied the spatial pattern of seed plant floristic elements in Yunnan Province of China. It was indicated that the proportions of cosmopolitan and temperate elements increased with increasing latitude, while those of tropical elements had a decreasing trend. Cluster analysis showed that the study area could be divided into two parts, with the latitude about 24.5°N as a division line. To the south of the line, the dominant flora was tropical elements, and the vegetation was dominated by tropical mountain rainforest, seasonal rain forest, monsoon rain forest, and monsoon evergreen broadleaved forest. To the north of the line, there were much greater proportions of temperate elements, and the vegetation was dominated by the evergreen, hard and broadleaved forest, temperate coniferous forest, coniferous and broadleaved mixed forest, alpine meadow, and evergreen broadleaved forest (moist or semimoist, showing strong floristic transition). This division line was different from “Tanaka Line”, possibly due to different study aims and contents.

Key words: Rice-duck mutualism, Nutrition ecology, Rice quality