Abstract: To better understand the ecological adaptability of alien species Flaveria bidentis, the anatomical characters of its vegetative organs were studied with scanning electron microscope and optical microscope. F. bidentis leaf was of isobilateral type, and had thicker epidermis cell wall and cuticle, obvious cryptopores, and highly developed palisade tissue, with typical C4-plant Kranz anatomy. The collenchymas and vascular tissue in stem and the aerenchyma in root were well developed. Secretory structure was found in all vegetative organs. According to the analyses of soil physical and chemical properties and relevant ecological factors, F. bidentis preferred to live under strong light and high temperature conditions, and exhibited strong tolerance against drought, saline/alkaline, and poor nutrients, being able to coexist with some drought- and salt-tolerant plants. It was suggested that the strong adaptability of F. bidentis to harsh environment had definite relations to the anatomical characters of its vegetative organs, being one of the causative factors responsible for the invasiveness of F. bidentis.

Key words: Chinese fir plantation, Natural secondary forest, Soil biological activity