A study site located at 2600 m elevation in Tartarchia Anpu, Nantou county, Taiwan, exhibits a unique grassland community composed of two principal species, Miscanthus transmorrisonensis and Yushinia niitakayamensis, and 35 other species. The relative frequencies of the two species are 12% and 11%, while their relative coverages are 25% and 19.5%, respectively. The values for the remaining 35 species are lower than 4% each, while species diversity of the community is -3.04839, indicating great diversity. To elucidate the mechanism of dominance of M. transmorrisonensis, allelopathic evaluation of the plant was conducted. Aqueous extracts of M. transmorrisonensis plant parts with two ecotypes were bioassayed. The extracts showed significant phytotoxic effects on seed germination and radicle growth of four tested plants: rye grass, lettuce, and two varieties of Chinese cabbage. In addition, rhizosphere soils under Miscanthus also exhibited significant phytotoxicity, indicating that allelopathic interaction was involved. Some responsible phytotoxic phenolics, namely, p-coumaric, ferulic, vanillic, protocatechuic, o-hydroxyphenylacetic, and m-hydroxyphenylacetic acids, and 4-hydroxycoumarin and phloridzin were identified. Allelopathy thus can play an important role in regulating plant diversity in the field.
