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Floristically, Taiwan is a very rich island due to her varied geography, topography and habitats. Through extended historical research involving past and present botanical inventories of the central mountains, particularly of the Hehuanshan area of Taiwan, we are now able to examine the floristic composition of four elevation zones, 2,000-2,500 m, 2,500-3,000 m, 3,000-3,500 m, and 3,500-3,950 m. We selected four study sites, namely Shinjenkan (SJK) at 2,250-2,585 m, Shihmenshan (SMS) at 3,000 m, Hehuan East Peak (HEP) at 3,401 m, and Hehuan Major Peak (HMP) at 3,408 m, and determined their α, β, and Y diversities along with their Simpson's diversity indices. Our results clearly showed that the species richness (α diversity) was significantly high and decreased as the altitude increased. Coincidently, Simpson's diversity index at 2,250 m was significantly high at 0.85, drastically decreased to 0.17 at 3,145 m, and continued to decrease to 0.10 at both sites at 3408 m. On the other hand, by comparing plant distribution data collected over a century for the Hehuanshan, Alishan and Yushan areas, we were able to predict that plants would migrate mostly from a lower to a higher elevation when the global temperature increases. For instance, in the Hehuanshan area, 16 species would move towards higher elevations and seven species would remain in their original zone. In the Alishan area, seven species would migrate and four would remain in their original zone, and in Yushan, 15 species would migrate out of their zone and five would remain. Of all of the species, at least six risk extinction, since their expected migration would take them far beyond the limits of the land available above 3,950 m. It is concluded that the alpine vegetation will be redistributed, many plant species will move towards a higher elevation and, eventually, at least six plant species (Anaphalis morrisonicola, Artemisia morrisonensis, Swertia randaiensis, Hypericum nagasawai, Angelica morrisonicola, and Cirsium arisanensis) will become extinct. [ABSTRACT FROM AUTHOR]